ASTM B946-23

Standard Test Methods for Surface Roughness of Powder Metallurgy (PM) Products

SIGNIFICANCE AND USE
3.1 The surface roughness of PM parts is an important characteristic in relation to factors such as their load-bearing, wear, sealing, sliding, adhesion, electrical contact, and lubricant retention properties.  
3.2 Surface roughness may also be critical for component assembly or system performance. Dimensional fit and mating surface interaction may require certain surface roughness requirements to meet performance specifications.
SCOPE
1.1 These test methods cover measuring the surface roughness of powder metallurgy (PM) products at all stages of manufacturing from green compact to fully hardened finished component.  
1.2 These test methods provide the definition and schematic of some common surface roughness parameters (Ra, Rt, and RzISO)  
1.3 This standard specifies two different standardized procedures for measuring the surface roughness of PM parts.  
1.3.1 Method 1 uses a conical stylus and a Gaussian filter.  
1.3.2 Method 2 uses a chisel (knife) edge stylus.  
1.3.3 Each test method results in a different measure of surface roughness and the results are not directly comparable.  
1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Jan-2023
• ICS: 25.220.40 - Metallic coatings
• ICS: 77.160 - Powder metallurgy
• Technical Committee: B09 - Metal Powders and Metal Powder Products
• Drafting Committee: B09.05 - Structural Parts

Relations

• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM E456-13A(2017)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E456-13A(2017)e3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E456-13ae2 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13a - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13ae1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13ae3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Aug-2013
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E456-12e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-May-2012
• Refers: ASTM E456-12 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-May-2012
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM E691-08 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Oct-2008
• Refers: ASTM E456-08e2 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2008
• Refers: ASTM E456-08e3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2008

Overview

ASTM B946-23: Standard Test Methods for Surface Roughness of Powder Metallurgy (PM) Products defines reliable procedures for measuring the surface roughness of PM components throughout all manufacturing stages, from green compacts to fully finished parts. Surface roughness is a key quality indicator for PM products, influencing properties such as load-bearing capacity, wear resistance, sealing effectiveness, sliding performance, adhesion, electrical contact performance, and the ability to retain lubricants. Ensuring appropriate surface texture is also critical for successful assembly, achieving specified tolerances, and optimal system integration.

Key Topics

• Scope of Application
  • Applicable to PM products at any manufacturing stage.
  • Two primary measurement methods: conical stylus with Gaussian filtering, and chisel (knife) edge stylus.
• Surface Roughness Parameters
  • Defines commonly used metrics: Ra (arithmetic average), Rt (maximum peak-to-valley height), and Rz (ISO ten-point height).
• Measurement Methods
  • Method 1: Utilizes a conical stylus and a Gaussian filter as per ISO 16610-21. Appropriate for general measurements where porosity does not dominate.
  • Method 2: Employs a chisel or knife edge stylus designed to minimize stylus drop into open porosity-a frequent characteristic of PM surfaces.
  • The two methods yield different (non-comparable) results; selection must be agreed upon between supplier and purchaser.
• Result Reporting
  • Results should include the measured roughness values, method details (stylus tip radius, filter, evaluation length, measurement direction), and test locations.
• Precision and Bias
  • Measurement precision assessed through interlaboratory studies.
  • Repeatability and reproducibility depend on stylus type and surface, highlighting the importance of method selection.

Applications

ASTM B946-23 is widely adopted in industries where powder metallurgy parts are used, such as automotive, aerospace, electronics, and industrial machinery. Surface roughness measurement according to this standard is crucial for:

• Quality control: Verifying that PM parts meet industry specifications or customer requirements.
• Functional performance: Ensuring optimal wear resistance, friction control, sealing, and lubrication behavior.
• Assembly and System Performance: Achieving correct dimensional fit and ensuring good mating between components.
• Research and Development: Supporting process optimization and new material development by providing quantitative, consistent surface texture data.

By following ASTM B946-23, manufacturers can improve product reliability, extend component service life, and enhance customer satisfaction.

Related Standards

Several other standards complement or are referenced within ASTM B946-23:

• ASME B46.1: Surface Texture (Surface Roughness, Waviness, and Lay) - general guidelines for surface measurement.
• ISO 16610-21: Linear Profile Filters: Gaussian Filters - addresses profile filtering used in surface metrology.
• MPIF Standard 58: Determination of Surface Finish of Powder Metallurgy Products - additional PM-specific guidance.
• ASTM E456: Terminology Relating to Quality and Statistics - for consistent terminology.
• ASTM E691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method.

These documents ensure measurement consistency and global compatibility throughout the powder metallurgy industry.

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Keywords: ASTM B946-23, surface roughness, powder metallurgy, PM products, test methods, Ra, Rt, Rz, conical stylus, chisel stylus, quality control, component assembly, surface finish, industry standards

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B946 − 23
Standard Test Methods for
Surface Roughness of Powder Metallurgy (PM) Products
This standard is issued under the fixed designation B946; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1.1 These test methods cover measuring the surface rough-
2.2 MPIF Standard:
ness of powder metallurgy (PM) products at all stages of
MPIF Standard 58 Method for Determination of Surface
manufacturing from green compact to fully hardened finished
Finish of Powder Metallurgy Products
component.
2.3 ASME Standard:
1.2 These test methods provide the definition and schematic
ASME B46.1 Surface Texture (Surface Roughness,
of some common surface roughness parameters (R , R , and
a t
Waviness, and Lay)
R )
zISO
2.4 ISO Standard:
1.3 This standard specifies two different standardized pro-
ISO 16610-21 Geometric Product Specifications (GPS) –
cedures for measuring the surface roughness of PM parts.
Filtration–Part 21: Linear Profile Filters: Gaussian Filters
1.3.1 Method 1 uses a conical stylus and a Gaussian filter.
3. Significance and Use
1.3.2 Method 2 uses a chisel (knife) edge stylus.
1.3.3 Each test method results in a different measure of
3.1 The surface roughness of PM parts is an important
surface roughness and the results are not directly comparable.
characteristic in relation to factors such as their load-bearing,
wear, sealing, sliding, adhesion, electrical contact, and lubri-
1.4 The values stated in SI units are to be regarded as
cant retention properties.
standard. The values given in parentheses after SI units are
provided for information only and are not considered standard.
3.2 Surface roughness may also be critical for component
1.5 This standard does not purport to address all of the assembly or system performance. Dimensional fit and mating
safety concerns, if any, associated with its use. It is the surface interaction may require certain surface roughness
responsibility of the user of this standard to establish appro- requirements to meet performance specifications.
priate safety, health, and environmental practices and deter-
4. Interferences
mine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accor-
4.1 Because many conventional PM materials contain open
dance with internationally recognized principles on standard-
porosity at the surface, special consideration should be taken
ization established in the Decision on Principles for the
when measuring surface roughness. As most roughness param-
Development of International Standards, Guides and Recom-
eters are defined by measuring the microscopic peaks and
mendations issued by the World Trade Organization Technical
valleys, the porosity in sintered powder metallurgy products
Barriers to Trade (TBT) Committee.
will negatively influence this value.
4.2 Because the direction of pressing may cause direction-
2. Referenced Documents
ality in surface roughness values, the direction of measurement
2.1 ASTM Standards:
should be specified and reported.
E456 Terminology Relating to Quality and Statistics
5. Apparatus
5.1 Method 1 (Conical Stylus):
These test methods are under the jurisdiction of ASTM Committee B09 on
Metal Powders and Metal Powder Products and is the direct responsibility of
Subcommittee B09.05 on Structural Parts. Available from Metal Powder Industries Federation (MPIF), 105 College Rd.
Current edition approved Feb. 1, 2023. Published February 2023. Originally East, Princeton, NJ 08540, http://www.mpif.org.
approved in 2006. Last previous edition approved in 2016 as B946 – 11 (2016). Available from American Society of Mechanical Engineers (ASME), ASME
DOI: 10.1520/B0946-23. International Headquarters, Two Park Ave., New York, NY 10016-5990, http://
For referenced ASTM standards, visit the ASTM website, www.astm.org, or www.asme.org.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Available from International Organization for Standardization (ISO), ISO
Standards volume information, refer to the standard’s Document Summary page on Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
the ASTM website. Switzerland, https://www.iso.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B946 − 23
5.1.1 Surface Finish Measuring Instrument—Suitable for
complying with ASME B46.1.
5.1.2 A profiling, contact, skidless instrument for measuring
displacements of a stylus relative to an external datum.
5.1.3 Stylus with an appropriate radius (for example, 2 μm,
5 μm, or 10 μm (0.00008 in., 0.0002 in., or 0.0004 in.)).
NOTE 1—Because the stylus tip is subject to wear and mechanical
damage, even when made of diamond, regular checks of the stylus are
recommended. Techniques for checking the stylus condition are discussed
in ASME B46.1.
5.2 Method 2 (Chisel (Knife) Edge Stylus):
5.2.1 Surface Finish Measuring Instrument—Suitable for
complying with ASME B46.1. FIG. 2 R Arithmetic Mean Roughness Value
a
5.2.2 Stylus—Chisel (knife) edge, 1.27 mm (0.050 in.)
length and 0.010 mm 6 30 % (0.0004 in. 6 30 %) tip radius as
shown in Fig. 1. The chisel tip shall be oriented so that its long
edge is perpendicular to the direction of travel of the probe.
6. Sampling, Test Specimens, and Test Units
6.1 The test surface shall be clean and free of any oil, dirt,
debris, or foreign material.
FIG. 3 R Maximum Peak-to-Valley Height
6.2 Sufficient surface area shall be available to permit t
multiple traverses by the measuring instrument.
evaluation length as shown in Fig. 4. R is also known as the ISO 10-point
z
6.3 The test surface shall be flat over a sufficient length (in
height parameter.
accordance with instrument instructions) to allow proper
7.1.3 Use a stylus with a tip radius of either 2 μm, 5 μm, or
movement of the stylus.
10 μm [0.00008 in., 0.0002 in., or 0.0004 in.] as agreed be-
7. Procedure
tween the producer and purchaser.
7.1.4 Use a Gaussian filtered profile (for example, ISO
7.1 Method 1 (Conical Stylus):
16610-21) with a cut-off agreed between the producer and the
7.1.1 Measure the surface roughness in accordance with
purchaser.
ASME B46.1 by using the following parameters:
7.1.5 Use a total evaluation length that is five times the
7.1.2 The surface roughness parameter to be measured
cut-off value. For example, if the cut-off is 0.8 mm (0.03 in.),
should be agreed upon by the producer and purchaser; for
the total evaluation length shall be 4 mm (0.16 in.).
example, R , R , R .
a t z
7.1.6 The PM parts producer and the purchaser shall agree
NOTE 2—R , is the arithmetic average value of the filtered roughness
a
on the desired location and direction for the surface roughness
profile determined from deviations about the centerline within the
measurement.
evaluation length I as shown in Fig. 2. R , is the maximum peak-to-valley
m t
height over the tested length (absolute value between the highest peak and
NOTE 3—If the roughness is higher than 4.0 R increase the cut-off so
a
lowest valley) as shown in Fig. 3. R , is the ten-point height, or the
z
that the evaluation length is longer. This is because the surface is so
absolute value of the five highest peaks and five lowest valleys over the
irregular that a longer evaluation length is necessary to obtain a real
statistical approach.
7.1.7 Place the surface finish instrument in a position
suitable for measuring the test sample.
7.1.8 Zero and verify the instrument ov
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: B946 − 11 (Reapproved 2016) B946 − 23
Standard Test MethodMethods for
Surface FinishRoughness of Powder Metallurgy (PM)
Products
This standard is issued under the fixed designation B946; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Scope*
1.1 This test method coversThese test methods cover measuring the surface finishroughness of powder metallurgy (PM) products
at all stages of manufacturing from green compact to fully hardened finished component.
1.2 This test method providesThese test methods provide the definition and schematic of some common surface finishroughness
parameters (R , R , and R )
a t zISO
1.3 This standard specifies two different standardized procedures for measuring the surface roughness of PM parts.
1.3.1 Method 1 uses a conical stylus and a Gaussian filter.
1.3.2 Method 2 uses a chisel (knife) edge stylus.
1.3.3 Each test method results in a different measure of surface roughness and the results are not directly comparable.
1.4 The values stated in inch-poundSI units are to be regarded as standard. The values given in parentheses are mathematical
conversions to after SI units that are provided for information only and are not considered standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and to safety, health, and environmental practices
and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
This test method isThese test methods are under the jurisdiction of ASTM Committee B09 on Metal Powders and Metal Powder Products and is the direct responsibility
of Subcommittee B09.05 on Structural Parts.
Current edition approved April 1, 2016Feb. 1, 2023. Published April 2016February 2023. Originally approved in 2006. Last previous edition approved in 20112016 as
B946 – 11. DOI: 10.1520/B0946-11R16.11 (2016). DOI: 10.1520/B0946-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B946 − 23
2.2 MPIF Standard:
MPIF Standard 58 Method for Determination of Surface Finish of Powder Metallurgy Products
2.3 ASME Standard:
ASME B46.1 Surface Texture (Surface Roughness, Waviness, and Lay)
2.4 ISO Standard:
ISO 16610-21 Geometric Product Specifications (GPS) – Filtration–Part 21: Linear Profile Filters: Gaussian Filters
3. Significance and Use
3.1 The surface finish of a component may be critical for certain applications, affecting properties such as wear resistance, fatigue
strength, and coefficient of friction.roughness of PM parts is an important characteristic in relation to factors such as their
load-bearing, wear, sealing, sliding, adhesion, electrical contact, and lubricant retention properties.
3.2 Surface finishroughness may also be critical for component assembly or system performance. Dimensional fit and mating
surface interaction may require certain surface finishroughness requirements to meet performance specifications.
4. Interferences
4.1 Because many conventional PM materials contain open porosity at the surface, special consideration should be taken when
measuring surface finish.roughness. As most roughness parameters are defined by measuring the microscopic peaks and valleys,
the porosity in sintered powder metallurgy products will negatively influence this value.
4.2 The use of a conical point stylus may result in inaccurate or inconsistent surface finish results because the sharper point of
the stylus may drop into open porosity on the surface of the component.
4.3 A chisel point stylus may be used for better accuracy and consistency.
4.2 Because the direction of pressing may cause directionality in surface finishroughness values, the direction of measurement
should be specified and reported.
5. Apparatus
5.1 Surface Finish Measuring Instrument.Method 1 (Conical Stylus):
5.1.1 Surface Finish Measuring Instrument—Suitable for complying with ASME B46.1.
5.1.2 A profiling, contact, skidless instrument for measuring displacements of a stylus relative to an external datum.
5.1.3 Stylus with an appropriate radius (for example, 2 μm, 5 μm, or 10 μm (0.00008 in., 0.0002 in., or 0.0004 in.)).
NOTE 1—Because the stylus tip is subject to wear and mechanical damage, even when made of diamond, regular checks of the stylus are recommended.
Techniques for checking the stylus condition are discussed in ASME B46.1.
5.2 Stylus—Method 2 (Chisel (Knife) Edge Stylus): Chisel point, 0.050 in. (1.27 mm) length and 0.0004 in. 6 30 % (0.010 mm
6 30 %) tip radius as shown in Fig. 1. To limit the possibility of the stylus dropping into open surface porosity, a chisel point stylus
is recommended. If a cone stylus is used, filtering software shall also be used to remove the influence of open surface porosity.
5.2.1 Surface Finish Measuring Instrument—Suitable for complying with ASME B46.1.
5.2.2 Stylus—Chisel (knife) edge, 1.27 mm (0.050 in.) length and 0.010 mm 6 30 % (0.0004 in. 6 30 %) tip radius as shown in
Fig. 1. The chisel tip shall be oriented so that its long edge is perpendicular to the direction of travel of the probe.
Available from Metal Powder Industries Federation (MPIF), 105 College Rd. East, Princeton, NJ 08540, http://www.mpif.org.
Available from American Society of Mechanical Engineers (ASME), ASME International Headquarters, Two Park Ave., New York, NY 10016-5990, http://
www.asme.org.
Available from International Organization for Standardization (ISO), ISO Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva, Switzerland,
https://www.iso.org.
B946 − 23
FIG. 1 Chisel (Knife) Edge Stylus for Surface FinishRoughness Measurement
6. Sampling, Test Specimens, and Test Units
6.1 The test surface shall be clean and free of any oil, dirt, debris, or foreign material.
6.2 Sufficient surface area shall be available to permit multiple traverses by the measuring instrument.
6.3 The test surface shall be flat over a sufficient length (in accordance with instrument instructions) to allow proper movement
of the stylus.
7. Procedure
7.1 The PM parts manufacturer and purchaser shall agree on the desired location and direction for surface finish measurement.
7.2 Place the surface finish instrument in a position suitable for measuring the test sample.
7.3 Zero and verify the instrument over the surface finish range expected for the test sample.
7.1 Place the test sample under the stylus and then lower the stylus to the measuring position in accordance with the instrument
instructions.Method 1 (Conical Stylus):
7.1.1 Measure the surface roughness in accordance with ASME B46.1 by using the following parameters:
7.1.2 The surface roughness parameter to be measured should be agreed upon by the producer and purchaser; for example,
R ,R ,R .
a t z
NOTE 2—R , is the arithmetic average value of the filtered roughness profile determined from deviations about the centerline within the evaluation length
a
I as shown in Fig. 2. R , is the maximum peak-to-valley height over the tested length (absolute value between the highest peak and lowest valley) as
m t
shown in Fig. 3. R , is the ten-point height, or the absolute value of the five highest peaks and five lowest valleys over the evaluation length as shown
z
in Fig. 4. R is also known as the ISO 10-point height parameter.
z
7.1.3 Use a stylus with a tip radius of either 2 μm, 5 μm, or 10 μm [0.00008 in., 0.0002 in., or 0.0004 in.] as agreed between the
producer and purchaser.
7.1.4 Use a Gaussian filtered profile (for example, ISO 16610-21) with a cut-off agreed between the producer and the purchaser.
7.1.5 Use a total evaluation length that is five times the cut-off value. For example, if the cut-off is 0.8 mm (0.03 in.), the total
evaluation length shall be 4 mm (0.16 in.).
7.1.6 The PM parts producer and the purchaser shall agree on the desired location and direction for the surface roughness
measurement.
B946 − 23
FIG. 2 R Arithmetic Mean Roughness Value
a
FIG. 3 R Maximum Peak-to-Valley Height
t
NOTE 3—If the roughness is higher than 4.0 R increase the cut-off so that the evaluation length is longer. This is because the surface is so irregular that
a
a longer evaluation length is necessary to obtain a real statistical approach.
7.1.7 Place the surface finish instrument in a position suitable for measuring the test sample.
7.1.8 Zero and verify the instrument over the surface roughness range expected for the test sample.
7.1.9 Place the test sample under the stylus and then lower the stylus to the measuring position in accordance with the instrument
instructions.
7.1.10 Measure the surface roughness of the test surface. A minimum of three traverses at different locations is recommend
...