ASTM G196-08(R2021) pdf free download

ASTM G196-08(R2021) pdf free download.Standard Test Method for Galling Resistance of Material Couples
1. Scope
1.1 This test method covers a laboratory test that ranks the galling resistance of material couples using a quantitative measure. Bare metals, alloys, nonmetallic materials, coatings, and surface modified materials may be evaluated by this test method. 1.2 This test method is not designed for evaluating the galling resistance of material couples sliding under lubricated conditions, because galling usually will not occur under lubricated sliding conditions using this test method. 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 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 appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.5 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Terminology
3.1 Definitions used in this test method are given in Termi- nology G40. 3.2 Definitions: 3.2.1 apparent area ofcontact—area ofcontact between two solid surfaces defined by the boundaries of their macroscopic interface. 3.2.2 galling—form of surface damage arising between sliding solids, distinguished by macroscopic, usually localized, roughening and creation of protrusions above the original surface; it often includes plastic flow or material transfer, or both. 3.2.3 triboelement—one of two or more solid bodies that comprise a sliding, rolling, or abrasive contact, or a body subjected to impingement or cavitation. (Each triboelement contains one or more tribosurfaces.) 3.2.4 tribosurfaces—any surface (of a solid body) that is in moving contact with another surface or is subjected to im- pingement or cavitation. 3.2.5 tribosystem—any system that contains one or more triboelements, including all mechanical, chemical, and envi- ronmental factors relevant to the tribological behavior. (See also triboelement.) 3.3 Definitions ofTerms Specific to This Standard: 3.3.1 galling 50 —stress at which the probability of galling occurring on one or both of the test specimens is 50%.
4. Summary of Test Method
4.1 This test method uses available laboratory equipment capable of maintaining a constant, compressive load between two flat specimens, such as hydraulic compression testing machines. One specimen is slowly rotated one complete revolution relative to the other specimen. The surfaces are examined for galling after sliding. The criterion for whether galling occurs is the appearance of the specimens based on unassisted visual examination. 4.2 Appropriate load intervals are chosen to determine the threshold galling stress within an acceptable range. 4.3 The higher the Galling 50 value, the more galling resis- tant is the test couple.
5. Significance and Use
5.1 This test method is designed to rank material couples in their resistance to the failure mode caused by galling and not merely to classify the surface appearance of sliding surfaces.5.2 This test method has been shown to have higher repeatability than Test Method G98 in determining the galling resistance. Test Method G98 can be used for initial ranking of galling resistance. 5.3 This test method should be considered when damaged (galled) surfaces render components non-serviceable. Experi- ence has shown that galling is most prevalent in sliding systems that are slow moving and operate intermittently. The galling and seizure of threaded components is a classic example that this test method most closely simulates. 5.4 Other galling-prone examples include: sealing surfaces of valves that may leak excessively due to galling and pump wear rings that may function ineffectively due to galling. 5.5 If the equipment continues to operate satisfactorily and loses dimension gradually, then galling is not present, and the wear should be evaluated by a different test method. 5.6 This test method should not be used for quantitative or final design purposes, since many environmental factors influ- ence the galling performance of materials in service. Lubrication, alignment, stiffness, and geometry are only some of the factors that can affect how materials perform. This test method has proven valuable in screening materials for proto- typical testing that more closely simulates actual service conditions.