ML22143A951

Draft Guidelines Document for Additive Manufacturing - Laser-Directed Energy Deposition

ML22143A951
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Issue date:	05/23/2022
From:	Anchondo-Lopez I NRC/NRR/DNRL/NVIB
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THE NRC STAFF HAS PREPARED THIS DRAFT DOCUMENT AND IS RELEASING IT TO SUPPORT THE JUNE 2022, PUBLIC MEETING ON ADVANCED MANUFACTURING TECHNOLOGIES. THIS DRAFT DOCUMENT IS SUBJECT TO CHANGE AND ITS CONTENT SHOULD NOT BE INTERPRETED AS OFFICIAL AGENCY POSITIONS. SUBSEQUENT TO THE PUBLIC WEBINAR, THE NRC STAFF PLANS TO CONTINUE WORKING ON THIS DOCUMENT AND COULD INCORPORATE STAKEHOLDER FEEDBACK RECEIVED AT THE PUBLIC WEBINAR.

Draft Guidelines Document for Additive ManufacturingLaser Directed Energy Deposition

1. Introduction and Purpose When finalized, this draft guidelines document (DGD) will provide U.S. Nuclear Regulatory Commission (NRC) staff with guidelines for conducting reviews of submittals that include components manufactured using additive manufacturinglaser directed energy deposition (L-DED). These guidelines are based on the NRC assessment of the impact on component performance of the identified differences between L-DED and traditional manufacturing methods as documented in NRC Technical Assessment of Additive ManufacturingLaser Directed Energy Deposition, (Agencywide Documents Access and Management System (ADAMS)

Accession No. ML21292A188) (hereafter, NRC technical assessment), which builds on the Oak Ridge National Laboratorys (ORNLs) technical information and gap analysis, Review of Advanced Manufacturing Techniques and Qualification Processes for Light Water Reactors Laser Directed Energy Deposition Additive Manufacturing, (ADAMS Accession No. ML21292A187). This document provides L-DED-specific draft guidelines under Subtask 2C, Action Plan for Advanced Manufacturing Technologies (AMTs), Revision 1, dated June 23, 2020 (ADAMS Accession No. ML19333B973), as a supplement to the AMT generic draft guidelines document, Draft AMT Review Guidelines (ADAMS Accession No. ML21074A037) (hereafter, draft generic guidelines).

When reviewing an AMT submittal, the NRC staff can refer to the generic guidelines, once finalized, which can assist the NRC staffs review of a submittal requesting the use of an AMT.

The finalized generic guidelines along with this DGD will identify the generic and L-DED-specific information that could be necessary in a submittal in order to provide a timely and efficient review. The NRC technical assessment is also available for additional background and technical information to support the review of a submittal.

2. Brief Description of the NRC Technical Assessment of Laser Directed Energy Deposition This section describes the purpose of the NRC technical assessment of L-DED, which provides the technical basis for the technical review guidelines described in this DGD. The primary objective of the NRC technical assessment is to describe the differences between an L-DED-fabricated component and a traditionally manufactured component, assess the impact that the identified difference has on component performance, and identify relevant technical information pertaining to these differences for L-DED-fabricated components. This DGD is intended to build on the NRC technical assessment and provide guidelines, when finalized, to

the NRC staff by identifying important considerations when reviewing a submittal requesting the use of L-DED.

The overall impact to plant safety (e.g., safety significance) is a function of component performance and the specific component application (e.g., its intended safety function). These reports do not address the impact on plant safety, as such an assessment would not be possible without considering a specific component application. In addition to the technical review guidelines in this document, the NRC staff should consider the specific component application and the potential for secondary consequences, such as debris generation and associated impacts, when assessing the impact to overall plant safety.

As discussed in the NRC technical assessment, the NRC staff identified differences between AMT and traditional manufacturing processes by reviewing the information and gap analysis rankings from the ORNL report, as well as other relevant technical information (e.g., NRC regulatory and research experience, technical meetings and conferences, codes and standards activities, Electric Power Research Institute and U.S. Department of Energy products and activities).

3. NRC Generic Guidelines for Advanced Manufacturing Technologies and Laser Directed Energy Deposition -Specific Guidelines The finalized generic guidelines will identify the information that could be necessary in a submittal to ensure a timely and efficient review. Appendix A to the generic guidelines identifies the five primary topics to be addressed in a submittal:

(1) Quality Assurance (QA): process followed during the manufacture and implementation of AMTs to ensure adherence to QA requirements (e.g., Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic licensing of production and utilization facilities, Appendix B, Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants), established methods (e.g., commercial -grade dedication), or both (2) Process Qualification: steps taken to demonstrate that the component will be produced with characteristics that will meet the intended design requirements (3) Supplemental Testing: testing conducted to demonstrate that those material and component properties required to meet the design requirements are acceptable in the applicable service environmental conditions, and thus the performance of the component in service will be acceptable (4) Production Process Control and Verification: steps taken to ensure that each component will be produced in accordance with the qualified process and, if the production process fails to meet the qualification essential variables, the steps taken to reestablish the qualified process (5) Performance Monitoring: actions taken to provide assurance that the component will continue to meet its design requirements until the end of its intended service life Table 1 includes the identified differences between L-DED and traditional manufacturing outlined in the NRC technical assessment (both generic and 316L material-specific) and identifies those primary elements from Appendix A to the generic guidelines that are expected to be most commonly applicable to each of the differences. However, the applicable primary elements may vary on a case-by-case basis, depending on the licensees approach to demonstrating quality and safety. Therefore, this table provides an example of applicable

elements and reflects that not every element in Appendix A to the generic guidelines is applicable to every difference listed in Table 1.

QA comprises all those planned and systematic actions necessary to provide adequate confidence that a system or component will perform satisfactorily in service. QA processes implemented during the manufacture and implementation of AMTs ensure that QA requirements (e.g., 10 CFR Part 50, Appendix B), established methods (e.g., commercial-grade dedication),

or both, have been satisfied. For AMTs, a QA program will specifically address novel or unique aspects of manufacturing or implementation specific to the AMT. Therefore, Table 1 does not explicitly include QA as a distinct column, but QA is applicable to each of the differences between traditional manufacturing and L-DED processes identified in the table and achieved through successful performance of the other four Appendix A items: process qualification, supplemental testing, production process control and verification, and performance monitoring.

Tables 2A and 2B provide the technical review guidelines. Table 2A lists the generic differences between traditional manufacturing and L-DED. Table 2B lists the material-specific differences between traditional manufacturing and L-DED 316L stainless steel. 316L is the alloy relevant to L-DED-fabricated nuclear applications with the most information currently available in the open literature. While Table 2B is also based on the available information in the open literature for 316L, the differences identified in Table 2B involving material-specific properties and performance would need to be considered for any newly fabricated material using L-DED.

In general, material-specific data for the proposed processing and post-processing parameters are important for any nuclear L-DED-fabricated component to ensure adequate component performance in the applicable environment, including properties (e.g., fracture toughness, tensile strength) and resistance to aging mechanisms (e.g., thermal aging, irradiation effects, and stress corrosion cracking (SCC)). It is important to note that the feedstock (i.e., powder vs.

wire) may impact the differences listed in the tables. The impact that feedstock selection has on a specific difference is noted as appropriate in Tables 2A and 2B.

Tables 2A and 2B provide technical review guidelines related to the differences for the L-DED process and component performance through the following columns:

• Difference: identifies the differences between L-DED and traditional manufacturing outlined in the NRC technical assessment

• Key Technical Information: summarizes the key technical information documented in the NRC technical assessment for easy reference

• Technical Review Guidelines: provides additional guidelines related to the differences between L-DED and traditional manufacturing that the staff should consider when evaluating how a licensees or applicants submittal addresses the differences between L-DED and traditional manufacturing It is important to note that a given submittal need not include all elements of these tables.

Table 1. Relevant Elements from Appendix A to the Generic Guidelines Process Supplemental Production Process Performance Difference Qualification Testing Control and Verification Monitoring L-DED Machine Process Control X X Powder Feedstock Quality X X Wire Feedstock Quality X X L-DED Build Process Management and Control X X Witness Specimens X X Thermal Post-Processing X X Local Geometry Impacts on Component Properties and X X Performance Heterogeneity and Anisotropy in Properties X X Residual Stress X X Porosity X X Surface Finish X X X Tensile Properties X X Initial Fracture Toughness X X Thermal Aging X X SCC and Corrosion Resistance X X Fatigue X X Irradiation Effects X X High Temperature Time-Dependent Aging Effects (e.g., X X

Creep and Creep-Fatigue)

Weld Integrity X X Weldability / Joining X X

Table 2A. Technical Information and Review GuidelinesL-DED Generic Difference Key Technical Information Technical Review Guidelines

• Control of L-DED files is needed to Process Qualification ensure process control. Improper

• The applicant should identify the essential variables related to L-DED machine file control can significantly impact process control and demonstrate that controlling these variables within identified final component properties and ranges will ensure reliable, adequate, and repeatable component properties and performance and affect fabrication performance.

replication. Cybersecurity,

• At a minimum, the process qualification should consider the following essential database traceability, managing variables:

software updates, and similar items o software file preparation (e.g., L-DED software version, and L-DED software L-DED are highly important to ensuring settings)

Machine end-use component quality. o calibration of L-DED machine and subsystems (e.g., build stage, feedstock Process

• Machine calibration is vital for deposition, laser optics, atmosphere control)

Control fabrication replication, particularly

• The applicant should identify additional specific essential variables and their ranges ensuring correct feedstock as appropriate.

deposition parameters, laser Production Process Control and Verification power, laser spot size, travel

• During production, the applicant should demonstrate that process control and speed, and atmospheric quality verification will maintain the production process within the qualified essential control in addition to geometric variable ranges.

tolerances. For LP-DED, this

• The applicant can use a variety of machine process controls approaches to includes contamination demonstrate process control and verification, including, but not limited to periodic minimization if recycling powder. machine calibration verification.

• Detailed powder characterization Process Qualification and control, preventing powder

• Through process qualification, the applicant should provide sufficient data to identify contamination, and maintenance of the essential variables related to powder quality and demonstrate that controlling an inert gas environment are these variables within identified ranges will ensure reliable and adequate important factors in ensuring component properties and performance.

powder quality and reducing

• At a minimum, the process qualification should consider the following essential powder variability. variables for powder quality:

Powder

• Powder contamination is a critical o chemical composition, including trace elements Feedstock issue that may adversely affect o powder size and morphology distribution Quality material properties and process by o powder flowability introducing oxides and changing o acceptance criteria or limits for powder reuse chemical composition.

• The applicant should identify additional specific essential variables and their ranges

• Thorough cleanliness activities, as appropriate.

dedication of LP-DED machines to Production Process Control and Verification specific alloys, and periodic

• During production, the applicant should demonstrate that process control and replacement of feedstock verification will maintain the production process within the qualified essential conveying tubes and components variable ranges.

Difference Key Technical Information Technical Review Guidelines can be conducted to address

• The applicant can use a variety of powder quality approaches to demonstrate powder contamination. process control and verification, including, but not limited to, the following:

• LP-DED can achieve high powder o testing final components on a sampling basis utilization exceeding 90% in some o characterizing essential variables by routine powder sampling before initial use cases, which makes powder reuse and reuse less essential than in LPBF. o implementing procedures to minimize powder contamination during production

• Powder reuse can provide substantial cost benefits but can introduce significant variability in powder composition. Powder characterization and associated acceptance criteria may be warranted to reuse powder, especially for safety significant components.

• Welding wire feedstock is almost Process Qualification always used for LW-DED

• Through process qualification, the applicant should provide sufficient data to identify applications that is certified by the the essential variables related to wire feedstock quality and demonstrate that manufacturer to conform to AWS or controlling these variables within identified ranges will ensure reliable and adequate ISO standards for the specific alloy component properties and performance.

and wire product in question.

• At a minimum, the process qualification should consider the following essential

• There is a long-established history variables for wire feedstock quality:

of ensuring welding consumables o chemical composition conform to applicable standards for o material homogeneity Wire industrial welding applications. o surface condition, e.g., roughness Feedstock

• Wire chemistry and processing- o size Quality path must be tightly controlled.

• The applicant should identify additional specific essential variables and their ranges

• Contamination concerns are well as appropriate.

understood and are less of a Production Process Control and Verification concern as compared to powder

• During production, the applicant should demonstrate that process control and feedstock. verification will maintain the production process within the qualified essential variable ranges.

• The applicant can use a variety of wire feedstock quality approaches to demonstrate process control and verification, including, but not limited to testing final components on a sampling basis.

Difference Key Technical Information Technical Review Guidelines

• Build interruptions (planned and Process Qualification unplanned) can have a very

• The applicant should identify the essential variables related to L-DED build process significant impact on quality of the management and control and demonstrate that controlling these variables will component and should be avoided. ensure reliable, adequate, and repeatable component properties and performance.

• In situ monitoring without feedback

• At a minimum, the process qualification should consider defining essential variables control can be used to identify with demonstration for the following:

issues in the build process in real o build interruption (e.g., duration, frequency, component location, and geometry) time and may be used in o loss of environmental control (e.g., event time, degree of air ingress).

conjunction with other approaches

• The applicant should identify additional specific essential variables as appropriate.

to demonstrate process control. Production Process Control and Verification

• In situ monitoring with feedback

• The applicant should demonstrate that process control and verification will maintain control is still a developing area of the production process within the qualified essential variable ranges.

L-DED Build research and should be carefully

• The applicant can use a variety of approaches to demonstrate process control and Process managed and strongly verification, including, but not limited to, the following:

Management demonstrated if proposed for use o monitoring build issues (e.g., incomplete spreading, delamination, or other and Control during production. events that may result in component rejection)

• Management, storage, retrieval, o confirming build parameters, such as chemical composition and contamination and analysis of the data generated (e.g., oxides) during the L-DED process is critical o for location-specific measurements, measuring of materials properties for accelerating process (e.g., strength, hardness), appropriately demonstrating how they are optimization, although proper representative of geometry, size, location, and spatial orientation identification, handling, and o confirming of expected material microstructure and characteristics (e.g., residual evaluation of this information is still stress, porosity, surface finish) under development. o scrapping any builds that deviate from the qualified essential variable ranges.

• Due to the lack of maturity of the approach, in situ monitoring with feedback control should be adequately supported with a strong basis on the effectiveness of the approach.

• The most highly representative test Process Qualification specimens are obtained from end-

• The applicant should identify the component properties and characteristics for use component geometries. which witness testing will be used to demonstrate process qualification.

o Geometry impacts, particularly o Component properties and characteristics for which witness testing could be Witness thickness, on witness specimen used include various microstructure and material properties (e.g., composition, Specimens microstructure and properties density, hardness, microstructure, tensile, fatigue, fracture toughness, corrosion should be considered and testing).

addressed.

• The applicant should demonstrate that witness specimens are representative of the

• Optimal witness specimen end-use component in terms of microstructure and material properties. At a parameters (geometry, size, minimum, the applicant should address the effects of differences between

Difference Key Technical Information Technical Review Guidelines location, spatial orientation, and the witness specimens and the end-use component (e.g., geometry, size, frequency) depends highly on the location, and spatial orientation).

end-use component geometry and o One acceptable approach would be to benchmark witness specimen results to the goal of the witness testing end-use component results.

approach (e.g., monitoring build

• The applicant should discuss the witness testing methodology with regard issues as part of process control or to evaluation technique and frequency.

generating representative material properties data as part of process Production Process Control and Verification qualification).

• The applicant should discuss how witness testing will be used for process control

• When sectioning end-use and verification such that essential variables will be maintained within the qualified geometries is not feasible, ranges during the production process.

functional evaluations the

• The applicant can use a variety of witness specimen approaches to relationship between the demonstrate process control and verification, including, but not limited to, the acceptability of the end-use following:

geometries (e.g., burst tests, o monitoring build issues (e.g., incomplete spreading, delamination, or other inspections) and the use of events that may result in component rejection) simplified witness specimen o confirming build parameters, such as chemical composition and contamination geometries would need to be (e.g., oxides) demonstrated. o for location-specific measurements, measuring of materials properties (e.g., strength, hardness), appropriately demonstrating how they are representative of geometry, size, location, and spatial orientation o confirming of expected material microstructure and characteristics (e.g., residual stress, porosity, surface finish)

Difference Key Technical Information Technical Review Guidelines

• Post-processing heat treatments Process Qualification without hot isostatic pressing (HIP)

• For process qualification, the applicant should identify appropriate thermal post-generally are designed to provide processing techniques for the fabricated component and demonstrate the intended two benefits: stress relief and/or effects of thermal post-processing on the final component.

annealing, but likely have little

• The applicant should provide sufficient data to identify the essential variables impact on porosity or flaws. related to thermal post-processing and demonstrate that controlling these variables o Stress relief heat treatments will within identified ranges will ensure reliable and adequate component properties and primarily reduce residual performance.

stresses from the as-built part

• At a minimum, the process qualification for thermal post-processing should consider without otherwise affecting the the following essential variables microstructure or properties. o for heat treatment: temperature profile over time, including heating rate, cooling o Annealing heat treatments rate, hold time at temperature, and environment during heat treatment should greatly reduce or o for HIP: temperature and pressure profile over time, including heating rate, eliminate residual stress as well cooling rate, hold time at temperature, and environment during heat treatment as coarsen the microstructure

• The applicant should identify additional specific essential variables as appropriate.

(to improve toughness) and reduce heterogeneity in Production Process Control and Verification microstructure and properties.

• During production, the applicant should demonstrate that process control and Thermal Post-

• HIP may be beneficial for reducing verification will maintain the production process within the qualified essential Processing residual stress, porosity, variable ranges for thermal post-processing.

heterogeneity, and internal cracks,

• The applicant can use a variety of approaches to demonstrate process control and while also coarsening the verification, including, but not limited to, the following:

microstructure (to improve o testing final components on a sampling basis toughness). o witness specimens

• For all thermal post-processing o validated monitoring of post-processing parameters during heat treatment or approaches, material-specific HIP process.

demonstration is important to identify adequate heat treatment or HIP parameters to achieve desired improvements in microstructure, properties, heterogeneity, porosity, and fabrication flaws.

• Thermal post-processing may significantly impact considerations related to the other L-DED-specific topics identified in lower rows (e.g.,

porosity, residual stress, initial fracture toughness).

Difference Key Technical Information Technical Review Guidelines

• The role of geometry on local Process Qualification microstructure and properties is

• Through process qualification, the applicant should provide sufficient data to one of the key differences between demonstrate that local geometry impacts on material properties and microstructure L-DED produced components and will be addressed to ensure reliable and adequate component properties and conventionally produced ones. performance.

• Local geometry significantly

• In the absence of demonstrated post-processing or build scan strategy to minimize impacts thermal profiles during or eliminate the local geometry impacts, the applicant needs to use an appropriate fabrication, which affects the local sampling methodology during process qualification to quantify the variability in microstructure and properties. materials properties and ensure adequate performance.

o For example, a thin section with

• The applicant should consider the following key factors affecting local geometry relatively rapid cooling rates will impacts by changing cooling rates and the resulting microstructure and properties:

likely have a much finer o local thickness variation microstructure than a thicker o local size or shape section with a slower cooling

• The applicant should identify additional specific key factors as appropriate.

rate due to more surrounding Supplemental Testing material being melted.

• The applicant should demonstrate that the local geometry impacts in an L-Local o As a result, local material DED-fabricated component will not unacceptably degrade material properties and Geometry properties such as strength, performance due to in-service aging.

Impacts on ductility and toughness will be o This demonstration should be performed on a sample that is representative of, Component affected by the variation in or bounds, the components qualified pre-service condition, including post-Properties microstructure as a function of processing.

and geometry.

Performance

• Post-processing and/or scan strategy refinement have the potential to minimize the local geometry impacts, however, the effects on properties and performance can vary significantly based on the geometry and materials used.

• If used, witness specimens representing the thinnest section are needed to bound material properties of component.

• The advantages of L-DED to fabricate components with as-built internal features can make inspection of the component features more difficult.

Difference Key Technical Information Technical Review Guidelines

• Heterogeneity generally manifests Process Qualification with different properties in the build

• Through process qualification, the applicant should provide sufficient data to direction relative to the other two demonstrate that heterogeneity and anisotropy in the L-DED build process will be directions due to the nature of the addressed to ensure reliable and adequate component properties and performance.

layer-by-layer build process. This

• In the absence of demonstrated thermal post-processing to minimize or eliminate impacts the microstructure and the heterogeneity, the applicant needs to use an appropriate sampling methodology fabrication defect structure and during process qualification to quantify the variability in materials properties and generally creates poorer properties ensure adequate performance.

Heterogeneity between build layers.

and

• Thermal post-processing with Anisotropy in appropriate parameters would be Properties expected to make material Supplemental Testing properties and performance more

• The applicant should demonstrate that the heterogeneity and anisotropy in an L-homogeneous and similar to DED-fabricated component will not unacceptably degrade material properties and conventional forged materials. performance through the service life of the component, including the effects of in-

• For example, in as-fabricated and service aging.

stress-relieved 316L, the variation o This demonstration should be performed on a sample that is representative of, in microstructure due to geometry or bounds, the components qualified pre-service condition, including thermal causes preferential crack growth post-processing.

directions for fatigue cracks.

• L-DED components typically Process Qualification experience significant as-fabricated

• Through process qualification, the applicant should provide sufficient data to residual stress. demonstrate that residual stress will be addressed to ensure reliable and adequate

• High residual stress may result in component properties and performance and prevent unacceptable warping, warping, cracking, and cracking, and delamination.

delamination; however, these

• Post-processing through heat treatment, HIP, or both, would be expected to events typically can be visually address residual stress but should be demonstrated.

detected.

Residual

• In addition, residual stress can Supplemental Testing Stress make the component susceptible to

• The applicant should address, by testing if necessary, that the residual stresses in future degradation such as SCC or an L-DED-fabricated component will not significantly increase the susceptibility to fatigue from the presence of high in-service degradation mechanisms, such as SCC or fatigue.

tensile residual stress on the o This demonstration can be performed on a sample that is representative of, or surface. bounds, the components qualified pre-service condition, including post-

• Thermal post-processing with processing.

appropriate parameters would be expected to relieve residual stress.

Difference Key Technical Information Technical Review Guidelines

• Porosity is known to adversely Process Qualification affect fatigue life, SCC, and

• Through process qualification, the applicant should provide sufficient data to irradiation-assisted stress corrosion demonstrate that porosity will be managed sufficiently to ensure reliable and cracking (IASCC), though the adequate component properties and performance.

precise quantitative impact

• Post-processing through heat treatment, HIP, or both, may significantly reduce depends on the material and porosity; the applicant should demonstrate this.

porosity characteristics (pore

• The applicant should consider the following key characteristics of porosity when frequency, pore size, pore assessing porosity:

morphology, and total void o pore density fraction). o pore distribution (e.g., location relative to the surface)

• Machine parameters and scan o pore size strategy refinement have the o pore morphology potential to address porosity o total void fraction concerns; however, they may vary

• The applicant should identify additional specific characteristics as appropriate.

Porosity significantly based on the geometry Supplemental Testing and materials used.

• The applicant should demonstrate that the porosity in an L-DED-fabricated

• Porosity is more prevalent in LP- component will not unacceptably degrade material properties and performance due DED than LW-DED due to the to in-service aging.

internal porosity and trapped gas in o This demonstration should be performed on a sample that is representative of, powder feedstock that does not or bounds, the components qualified pre-service condition, including post-exist in wire feedstock. processing.

• For post-processing, HIP with appropriate parameters has been demonstrated to reduce porosity and produce properties more similar to conventionally forged materials.

• Surface roughness is generally Process Qualification greater in as-built L-DED parts

• Through process qualification, the applicant should provide sufficient data to compared to similar forged demonstrate that surface roughness will be managed sufficiently to ensure reliable Surface materials. and adequate component properties and performance.

Finish o The layer-by-layer nature of LP-

• Post-processing through precision machining, shot peening, or other surface DED combined with the treatment may be able to significantly reduce surface roughness but should be tendency to weld unmelted demonstrated.

Difference Key Technical Information Technical Review Guidelines powder particles to the Supplemental Testing component surfaces produces a

• The applicant should demonstrate that the surface finish in an L-DED-fabricated rough outer surface in LP-DED. component will not unacceptably degrade material properties and performance due o LW-DED typically has a bead- to in-service aging.

like surface due to the layer-by- o This demonstration should be performed on a sample that is representative of, layer deposition but does not or bounds, the components qualified pre-service condition, including post-have the added roughness of processing.

attached particles. Production Process Control and Verification

• Higher surface roughness can lead

• During production, the applicant should demonstrate that process control and to reduced fatigue life and reduced verification will maintain the production process within the qualified essential SCC and corrosion resistance. variable ranges for post-processing.

• Surface finish can be improved by

• The applicant can use a variety of approaches to demonstrate process control and post-processing such as verification, including, but not limited to, the following:

subtractive machining, or other o testing final components on a sampling basis surface treatments. o validated monitoring of post-processing parameters.

• For components with complicated geometries, hybrid manufacturing approaches (iterating between additive and subtractive steps) may be necessary to reach all surfaces for post-processing.

Table 2B. Technical Information and Review GuidelinesL-DED 316L Material-Specific Difference Key Technical Information Technical Review Guidelines

• High porosity would likely Process Qualification/Supplemental Testing degrade tensile performance

• For process qualification and supplemental testing, the applicant should provide an but would have a greater analysis, supported by sufficient data in representative or bounding environments, to impact on other material show adequate tensile properties for the design of the component.

Tensile properties. o The corresponding analysis can demonstrate acceptable safety margins using Properties approaches such as the following:

demonstrating equal or superior performance by comparison to tensile properties for conventionally manufactured materials analyzing design requirements to demonstrate sufficient tensile properties for the component

• Limited data on 316L L-DED Process Qualification/Supplemental Testing materials have shown

• For process qualification and supplemental testing, the applicant should provide an significantly lower initial analysis, supported by sufficient data in representative or bounding environments, to fracture toughness show adequate fracture toughness for the intended function of the component.

depending on post- o The corresponding analysis can demonstrate acceptable safety margins using processing than similar approaches such as the following:

forged materials. This may demonstrating equal or superior performance by comparison to fracture be due to porosity or other toughness for conventionally manufactured materials defects that may be reduced analyzing design requirements to demonstrate sufficient fracture toughness for with optimized processing design and flaw evaluation purposes parameters and thermal Initial Fracture post-processing.

Toughness o However, 316L L-DED is still expected to have adequate initial toughness.

• Data in representative environments is important to demonstrate that fracture toughness will be adequate to meet component design assumptions.

• Thermal post-processing with appropriate parameters would be expected to improve fracture toughness.

Thermal Aging

• Data in representative Supplemental Testing/Performance Monitoring environments is important to

Difference Key Technical Information Technical Review Guidelines demonstrate that fracture

• Through supplemental testing and performance monitoring, the applicant should provide toughness does not degrade an analysis, supported by sufficient data in representative or bounding environments, to excessively due to thermal show adequate fracture toughness after thermal aging throughout the service life of the aging and will be adequate to component.

meet component design o The corresponding analysis can demonstrate acceptable safety margins using assumptions. approaches such as the following:

• Thermal post-processing with demonstrating equal or superior performance by comparison to fracture appropriate parameters toughness after thermal aging for conventionally manufactured materials would be expected to make addressing uncertainties in the data on fracture toughness after thermal aging material properties and and the implications to in-service performance through conservative design performance more similar to assumptions, additional margins in analyses, surveillance programs, or additional conventional forged performance monitoring materials.

• Data in representative Supplemental Testing/Performance Monitoring environments is important to

• Through supplemental testing and performance monitoring, the applicant should provide demonstrate that changes in an analysis, supported by sufficient data in representative or bounding environments, to material performance due to show adequate SCC and corrosion resistance for the intended function of the SCC will not be degraded to component.

a greater degree in L-DED o The corresponding analysis can demonstrate acceptable safety margins by using materials than forged approaches such as the following:

materials. demonstrating equal or superior performance by comparison to SCC and

• Post-processing with corrosion resistance performance for conventionally manufactured materials appropriate parameters addressing uncertainties in the data on SCC and corrosion resistance and the SCC and would be expected to make implications to in-service performance through additional performance monitoring Corrosion material properties and as appropriate Resistance performance more similar to conventional forged materials.

• In 316L, the silicon content in the powder can create oxides that have adverse effects on SCC growth rates.

Consideration should be given on oxide content in powder acceptance (virgin and recycled) criteria.

Fatigue

• Without adequate post- Supplemental Testing/Performance Monitoring processing, surface

Difference Key Technical Information Technical Review Guidelines roughness is known to be a

• Through supplemental testing and performance monitoring, the applicant should provide greater issue with L-DED an analysis, supported by sufficient data in representative or bounding environments and materials and can reduce loading conditions, to show adequate fatigue performance throughout the service life of fatigue life. the component.

• Fatigue properties are also o The applicant can use current fatigue management approaches supported by dependent on post- sufficient data for L-DED 316L to manage metal fatigue (e.g., cumulative usage processing heat treatment factors, cycle counting, EAF penalty factors).

and component porosity. o The corresponding analysis can demonstrate acceptable safety margins by using

• Limited data suggest high- approaches such as the following:

cycle fatigue life may be demonstrating equal or superior performance by comparison to fatigue testing for reduced compared to conventionally manufactured materials conventional 316L, while low- addressing uncertainties in the data on fatigue and the implications to in-service cycle fatigue life is performance through conservative design assumptions, additional margins in comparable to conventional analyses, surveillance programs, or additional performance monitoring 316L.

• Stress-relieved (without annealing heat treatment) L-DED 316L shows anisotropic fatigue strength and preferential crack growth directions due to the columnar microstructure.

• Data in representative environments is important to support fatigue calculations including environmentally-assisted fatigue (EAF) in L-DED materials.

• Data in representative Supplemental Testing/Performance Monitoring environments is important to

• Through supplemental testing and performance monitoring, the applicant should provide demonstrate that irradiation an analysis, supported by sufficient data in representative or bounding environments, to Irradiation effects will not be show adequate performance after irradiation (including irradiation-assisted SCC and loss Effects significantly greater in L-DED of toughness) for the intended function of the component throughout its service life.

materials than forged o The corresponding analysis can demonstrate acceptable safety margins by using materials. approaches such as the following:

• Post-processing with demonstrating equal or superior performance by comparison to irradiation effects appropriate parameters for conventionally manufactured materials would be expected to make

Difference Key Technical Information Technical Review Guidelines material properties and addressing uncertainties in the data on irradiation effects and the implications to performance more similar to in-service performance through conservative design assumptions, additional conventional forged margins in analyses, surveillance programs, or additional performance monitoring materials.

• Current studies point to reduced irradiation induced defects in L-DED components compared to conventional manufacturing.

However, the understanding is very limited, and research is ongoing. Additional research is likely needed to understand performance differences.

• For high temperature Supplemental Testing/Performance Monitoring operating environments (as

• Through supplemental testing and performance monitoring, the applicant should provide discussed in ASME Code an analysis, supported by sufficient data in representative or bounding environments, to Section III, Division 5), data show adequate performance after high temperature time-dependent aging effects in representative (including creep and creep-fatigue) for the intended function of the component throughout environments are important its service life.

High to demonstrate that high o The corresponding analysis can demonstrate acceptable safety margins by using Temperature temperature time-dependent approaches such as the following:

aging effects in L-DED demonstrating equal or superior performance by comparison to high temperature Time-Dependent materials will be equivalent to time-dependent aging effects for conventionally manufactured materials Aging Effects or acceptable when addressing uncertainties in the data on high temperature time-dependent aging compared to forged effects and the implications to in-service performance through conservative (e.g., Creep and Creep- materials. design assumptions, additional margins in analyses, surveillance programs, or Fatigue)

• Post-processing with additional performance monitoring appropriate parameters would be expected to make material properties and performance more similar to conventional forged materials.

Difference Key Technical Information Technical Review Guidelines

• Data in representative Supplemental Testing/Performance Monitoring environments is important to

• Through supplemental testing and performance monitoring, the applicant should provide demonstrate that welds with an analysis, supported by sufficient data in representative or bounding environments, to L-DED base materials will show adequate performance of the weld throughout the service life of the component.

perform similarly to those o This analysis can be informed by relevant experience and knowledge of performance with conventionally of welds of conventional materials along with potential limited -scope testing on welds manufactured base of L-DED materials.

materials. o The corresponding analysis can demonstrate acceptable safety margins by using Weld Integrity approaches such as the following:

demonstrating equal or superior performance by comparison to weld performance for conventionally manufactured materials addressing uncertainties in the data on weld performance and the implications to in-service performance through conservative design assumptions, additional margins in analyses, or additional performance monitoring

• There is very limited Process Qualification/Production Process Control and Verification published information on the

• Through process qualification and production process control and verification, the results of traditional joining applicant should provide sufficient data to demonstrate that weldability using traditional methods being used on L- arc welding or other joining processes that may be required for component installation in DED components service can be performed consistently and reliably with sufficient quality to meet Code

• Higher oxygen content, acceptance criteria.

residual stress, and o This should include careful consideration of unique aspects of L-DED-fabricated microstructural segregation materials compared to traditional manufacturing methods, including local geometry Weldability /

may affect the optimal impacts on material properties (e.g., fracture toughness) and Joining parameters for welding on L- heterogeneity/anisotropy, which are described in greater detail previously in this DED 316L compared to document.

conventional 316L.

• Weldability should be demonstrated for L-DED materials, but the existing welding standards and demonstration processes should be sufficient.