Studies of high temperature sliding wear of metallic dissimilar interfaces - II: Incoloy MA956 versus Stellite 6

摘要

The development of wear surfaces formed during limited debris retention sliding wear of Incoloy MA956 against Stellite 6 between room temperature and 750 ℃, and sliding speeds of 0.314 and 0.905 m s{sup}(-1) (7 N applied load, 4522m sliding distance) were investigated. At 0.314ms{sup}(-1), mild oxidational wear was observed at all temperatures, due to oxidation of Stellite 6-sourced debris and transfer to the Incoloy MA956; this debris separated the Incoloy MA956 and Stellite 6 wear surfaces. Between room temperature and 450 ℃, the debris mainly took the form of loose particles with limited compaction, whilst between 510 ℃ and 750 ℃ the debris were compacted and sintered together to form a Co-Cr-based, wear protective 'glaze' layer. The behaviour was identical to that previously observed on sliding Nimonic 80A versus Stellite 6 at 0.314ms{sup}(-1). At 0.905 ms{sup}(-1), mild oxidational wear was only observed at room temperature and 270 ℃ and dominated by Incoloy MA956-sourced debris. At 390 and 450 ℃, the absence of oxide debris allowed 'metal-to-metal' contact and resulted in intermediate temperature severe wear; losses in the form of ejected metallic debris were almost entirely Incoloy MA956-sourced. This severe wear regime was also observed from 510 up to 630 ℃, but increasingly restricted to the early stages of wear by development of a wear protective Incoloy MA956-sourced 'glaze' layer. This 'glaze' layer formed so rapidly at 690 ℃ and 750 ℃, that severe wear was all but eliminated and wear levels were kept low. The behaviour observed for Incoloy MA956 versus Stellite 6 at 0.905ms{sup}(-1) contrasts sharply with that previously observed for Nimonic 80A versus Stellite 6, in that the Incoloy MA956-sourced high Fe-Cr debris formed a protective oxide 'glaze', whilst the Nimonic 80A-sourced Ni and Cr oxides formed an abrasive oxide that at high sliding speeds assisted wear. The data indicates that the tendency of oxide to form a 'glaze' is readily influenced by the chemistry of the oxides generated.