Tribological properties of Al-Ni-Co-Si quasicrystalline coatings against Cr-coated cast iron disc

Abstract

The tribological behavior of Al-Ni-Co-Si quasicrystalline (QC) coatings prepared by air plasma spray (APS) and high velocity oxy-fuel (HVOF) techniques was investigated in dry sliding condition against a Cr-coated cast iron disc. Tests were performed for different parameters of the load, sliding velocity, and temperature under a reciprocal motion. Our results demonstrated the influence of the coating microstructure on the frictional and wear behavior. Values of the coefficient of friction measured for HVOF coatings against Cr-coated cast iron disc were found to be about 14% lower than those of APS coatings. Under the standard condition, HVOF coatings exhibited a better wear resistance than APS coatings, however, this difference was reduced for tests performed under the highest values of the load and temperature investigated in this study. The sliding conditions imposed in this study led to significant modifications of the contacting surfaces characterized by the formation of a transfer film on the counterpart material, densification of the coating subsurface, and generation of wear particles. The variations of the coefficient of friction with the testing parameters were explained by the third body concept. It was also shown that the wear performance was dependent on the local surface properties of the QC coatings. (C) 2002 Elsevier Science B.V. All rights reserved.