Transfer of elements and MML across the interface during reciprocal dry sliding wear of Al-SiCp MMC against steels

During dry sliding wear, extrinsic factors need to be examined (sliding speed, debris reprocessing, counterface, oxides) as they relate specifically to mechanically mixed layer (MML) formation, allowing its wear resistance to be more fundamentally understood. Effort is taken to understand the transfer of elements and counterface material that occurs in forming mechanically mixed layers between sliding surfaces by using different counterface materials in dry sliding contact against composite aluminum. The three counterface materials, 316 stainless steel, 440C, and 52100 bearing steel were tested against A356 Al-20% SiC to compare elemental transfer and MML formation behaviour. Unlubricated reciprocal, ball on block, testing was chosen to examine its effect on the reprocessing of debris between surfaces in contact and to help further understand how contact geometry affects mechanical mixing. It was observed that under reciprocating motion a MML caused by transfer of steel across the interface is less likely to form on the Al-MMC. Mixing of elements of both surfaces is seen to be limited by mass transfer of the Al-MMC to the steel counterface. The formation of a mechanically mixed layer is proposed to depend more on the process of delamination and debris particle dynamics than on the hardness or composition of the counterface during sliding wear. (author)