ASTM B875-96(2018)
(Specification)Standard Specification for Aluminum Diffusion Coating Applied by Pack Cementation Process
Standard Specification for Aluminum Diffusion Coating Applied by Pack Cementation Process
ABSTRACT
This specification covers the requirements for aluminum diffusion of metals applied by pack cementation process. The three classes of aluminum diffusion coating, defined by the type of base metal, are as follows: Class I (carbon and low alloy steels); Class II (stainless steels); and Class III (nickel-based alloys). Specimens shall adhere to processing requirements such as substrate preparation, high and low activity pack mix, materials (masteralloys, activators, and inert fillers), loading, furnace cycle, post cleaning, diffusion heat treatment, post straightening, visual inspection, and marking and packaging. Specimens shall also adhere to coating requirements such as diffusion thickness, aluminum content, appearance, and mechanical properties (tensile strength, and macro- and micro-hardness).
SCOPE
1.1 This specification covers the requirements for aluminum diffusion of metals by the pack cementation method. Pack diffusion employs the chemical vapor deposition of a metal which is subsequently diffused into the surface of a substrate at high temperature. The material to be coated (substrate) is immersed or suspended in a powder containing aluminum (source), a halide salt (activator), and an inert diluent such as alumina (filler). When the mixture is heated, the activator reacts to produce an atmosphere of aluminum halides which transfers aluminum to the substrate for subsequent diffusion. The aluminum-rich surface enhances corrosion, thermal stability, and wear-resistant properties.
1.2 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.
1.3 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
Relations
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: B875 −96 (Reapproved 2018)
Standard Specification for
Aluminum Diffusion Coating Applied by Pack Cementation
Process
This standard is issued under the fixed designation B875; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope B697Guide for Selection of Sampling Plans for Inspection
of Electrodeposited Metallic and Inorganic Coatings
1.1 Thisspecificationcoverstherequirementsforaluminum
B762Test Method of Variables Sampling of Metallic and
diffusion of metals by the pack cementation method. Pack
Inorganic Coatings
diffusion employs the chemical vapor deposition of a metal
C664Test Methods for Thickness of Diffusion Coating
whichissubsequentlydiffusedintothesurfaceofasubstrateat
D3951Practice for Commercial Packaging
high temperature. The material to be coated (substrate) is
immersed or suspended in a powder containing aluminum
3. Terminology
(source), a halide salt (activator), and an inert diluent such as
alumina (filler). When the mixture is heated, the activator
3.1 Definitions used in this specification are in accordance
reacts to produce an atmosphere of aluminum halides which
with Terminology B374.
transfers aluminum to the substrate for subsequent diffusion.
3.2 Definitions of Terms Specific to This Standard:
The aluminum-rich surface enhances corrosion, thermal
3.2.1 diffusion coating—a diffusion coating is one produced
stability, and wear-resistant properties.
bycausinganelementtoreactwithordiffuseinto,orboth,the
1.2 This standard does not purport to address all of the
surface of a metallic substrate, thus, chemically altering the
safety concerns, if any, associated with its use. It is the
surface of the substrate.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3.2.2 retorts—containers in which powder and parts are
mine the applicability of regulatory limitations prior to use.
packed for processing. They can be constructed of carbon,
1.3 This international standard was developed in accor-
stainless, or high alloys and fabricated in all shapes and sizes
dance with internationally recognized principles on standard-
to accommodate parts being processed.
ization established in the Decision on Principles for the
3.2.3 significant surface—areas that are essential to the
Development of International Standards, Guides and Recom-
serviceabilityorfunctionofthearticle.Thesesurfacesmustbe
mendations issued by the World Trade Organization Technical
identifiedonadrawingormarked-upsampleofproduct.Areas
Barriers to Trade (TBT) Committee.
can fall into one of three categories as follows:
2. Referenced Documents
3.2.4 coating required—these surfaces must be in accor-
2.1 ASTM Standards:
dance with all quality requirements of this specification.
B374Terminology Relating to Electroplating
3.2.5 no coating required—these surfaces are areas where
B487Test Method for Measurement of Metal and Oxide
no coating is allowed due to a number of reasons including
Coating Thickness by Microscopical Examination of
dimensional, fabrication, and welding, as well as others.
Cross Section
Materials used for masking are commercially available.
B602Test Method for Attribute Sampling of Metallic and
Inorganic Coatings
3.2.6 optional—these surfaces do not require coating, but at
the same time do not require masking.
This specification is under the jurisdiction of ASTM Committee B08 on
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
4. Classification
B08.03 on Engineering Coatings.
Current edition approved June 1, 2018. Published June 2018. Originally
4.1 Therearethreeclassesofaluminumdiffusiondefinedby
approvedin1996.Lastpreviouseditionapprovedin2013asB875–96(2013).DOI:
base (basis) metal category.
10.1520/B0875-96R18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 4.1.1 Class I—Carbon steel and low alloy.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.1.2 Class II—Stainless steels.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 4.1.3 Class III—Nickel-based alloys.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B875 − 96 (2018)
5. Ordering Information 6.4.2 Low-activity packs are heated to a temperature be-
tween1650and2100°Fandheldfortheamountoftimeneeded
5.1 In order to make the application of this specification
to produce the desired depth of diffusion.
complete,thepurchasershallsupplythefollowinginformation
to the vendor through a purchase order and drawings:
NOTE3—Duetothehightemperatureoftheprocess,apositivepressure
ofaninertgas,usuallyargon,mustbemaintainedinretortsthroughoutthe
5.1.1 Title,ASTM designation number, and date of issue of
entire furnace cycle.
this specification.
6.5 Post-Cleaning—Retorts should be allowed to cool suf-
5.1.2 Deposit by classification (see Section 4).
ficiently before opening.When parts are removed from retorts,
5.1.3 Composition and metallurgical condition of substrate
residual pack mix is removed from surfaces by a supplier-
to be coated.
approved method.
5.1.4 Location of significant surfaces (see 3.2.3).
6.6 Diffusion Heat Treatment—Parts processed in high ac-
5.1.5 Samples for destructive metallurgical test (see 8.1).
tivity packs are placed in the retort and under inert atmosphere
5.1.6 Any post heat treatment required.
ofargonorhydrogenareheatedto1900to2000°Fandheldfor
5.1.7 Acceptance inspection procedure to be used (see
the amount of time needed to produce the desired level of
Section 9).
diffusion.
5.1.8 Any requirement for certification (see Section 11).
6.7 Post-Straightening—Long tubes may have distortion
6. Processing Requirements
due to the high temperature of process. Use rotary straightener
or hydraulic press to restore straightness and ovality.
6.1 Substrate Preparation—The metal to be aluminized
shallbefreeofflawsanddefectsthatwillbedetrimentaltothe 6.8 Visual Inspection—Inspect in accordance with 7.3.
coating. Thorough cleaning is essential to ensure satisfactory
6.9 Marking and Packaging—To be defined by the pur-
diffusion. Materials used for cleaning should not damage the
chaser in the purchase order. Parts processed for the U.S.
base metal. Oils, dirt, grease, and stains must be removed.
government and military, including subcontracts, shall be
Whenblastingisalsorequired,usealuminumoxide(90to220
packaged in accordance with Practice D3951.
mesh) at 60 to 80 psi from 4 to 6 in. standoff.
7. Coating Requirements
6.2 Pack Mix—Can be categorized by the following:
6.2.1 Types of Activity: 7.1 Diffusion Thickness—The following are minimums for
the different classes of materials based on standard process
6.2.1.1 High Activity—Deposit aluminum rapidly and per-
parameters. Thicker coatings require special processing and
form at temperatures (1000 to 1500°F). This is usually fol-
must be called out for in the purchase order if required.
lowed by a diffusion heat treatment at (1900 to 2000°F).
6.2.1.2 Low Activity—Deposit aluminum slowly and per- Class Minimum, in.
Class I (carbon and low alloy) 0.005
form at temperatures in excess of 1650°F.
Class II (stainless steels) 0.003
6.2.2 Materials:
Class III (nickel-base alloys) 0.001
6.2.2.1 Masteralloy with 50 to 100 % Pure Aluminum
7.2 Aluminum Content—The outer 15% of coating shall
—Sold under a number of trade names in various mesh sizes.
contain a minimum of 28% (by weight) aluminum.
Percentag
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.