The sliding wear behaviour of reactively hot pressed nickel aluminides

The sliding wear behaviour of reactively hot pressed nickel aluminides has been studied. The influence of load and intermetallic stoichiometry on wear rate has been considered using a block-on-ring test method with 440C as the counterface material. The results show that wear rate increases linearly with load and decreases as the nickel content increases. Stoichiometric NiAl exhibits wear rates similar to 440C, with material removal proceeding by the formation of sub-surface voids and cracks and the generation of plate-like wear debris typical of a delamination mechanism. The higher nickel containing materials such as Ni-40% Al, undergo severe deformation with the formation of an ultra-fine grained sub-surface region. The hardness of this region exceeds 750 Hv. Metal transfer from the 440C counterface is followed by oxidation of the transferred film to form a FeO rich layer resulting in mild wear and an order of magnitude reduction in wear rate compared with NiAl and 440C. (C) 1998 Elsevier Science S.A. All rights reserved.