Active Standard ASTM B874 | Developed by Subcommittee: B08.03
Book of Standards Volume: 02.05
Historical (view previous versions of standard)
This specification covers the requirements for chromium diffusion of metals applied by pack cementation process. The four classes of chromium diffusion coating, defined by the type of base metal, are as follows: Class I (carbon steels); Class II (low-alloy steels); Class III (stainless steels); and Class IV (nickel-based alloys). Specimens shall adhere to processing requirements such as substrate preparation, materials (masteralloys, activators, and inert fillers), loading, furnace cycle, post cleaning, post straightening, visual inspection, and marking and packaging. Specimens shall also adhere to coating requirements such as diffusion thickness, decarburization, chromium content, appearance, and mechanical properties (tensile strength, and macro- and micro-hardness).
This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.
1.1 This specification covers the requirements for chromium 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 chromium (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 chromium halides which transfers chromium to the substrate for subsequent diffusion. The chromium-rich surface enhances corrosion, thermal stability, and wear-resistant properties.
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 determine the applicability of regulatory limitations prior to use.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
B374 Terminology Relating to Electroplating
B487 Test Method for Measurement of Metal and Oxide Coating Thickness by Microscopical Examination of Cross Section
B602 Test Method for Attribute Sampling of Metallic and Inorganic Coatings
B697 Guide for Selection of Sampling Plans for Inspection of Electrodeposited Metallic and Inorganic Coatings
B762 Test Method of Variables Sampling of Metallic and Inorganic Coatings
C664 Test Methods for Thickness of Diffusion Coating
D3951 Practice for Commercial Packaging
E766 Practice for Calibrating the Magnification of a Scanning Electron Microscope
E1077 Test Methods for Estimating the Depth of Decarburization of Steel Specimens
F1330 Guide for Metallic Abrasive Blasting to Descale the Interior of Pipe
ICS Number Code 25.220.40 (Metallic coatings)