Definitions Revised ceramic second phase, material lot, and metallic phase definitions to keep consistent with F2730. Added discussion for material lot. Added definition for snowflakes, which was revised from the one in F2730. Added definitions for color variation, cracks (from F2730), c-cracks, cuts, metallic smears (from F2730), pits (from F2730), porosity (from F2730), pressing defects (from F2730), scratches, and scuffs. Added definition for raw material lot. Starting Powder Composition Changed the wording of 6.2 and Table 1 so that the starting powder composition requirements only apply to a Class I material. Lower class materials can be made with lower cost powders that dont meet the current specification. However, the requirement should be kept for Class I materials to provide additional assurance of quality since Class I materials are used for the most critical applications. Ideally, there would be no material composition specifications in the standard at all. But until we can incorporate an RCF test that confirms the performance level of the material, we need to try to assure that materials that meet the Class I requirements will provide Class I performance in bearing applications. Requiring high quality powder to be used is one part of providing this assurance. Inspection and Verification Changed the word defects to observable indications. Not everything that is seen is a defect as to me that means it is rejectable. It is only rejectable, and therefore a defect if the customer and vendor agree that it is based on some established criteria based on the customer and application requirements. This is my opinion of how this should be worded so Ill throw it out there and see what other people say. Changed the list of observable indications to divide up into those of material origin (not using the word faults), processing origin, and material or processing origin to make it consistent with how ASTM F2730 is organized. All the listed observable indications have associated definitions now.
Keywordsball bearings; bearing balls; ceramic; silicon nitride; Si
Ballot Item Approved as F2094/F2094M-2014 and Pending Publication