Influence of the heat treatment on the tribological behavior of a Ni-P-BN(h) autocatalytic composite coating

Sliding wear experiments were performed in order to evaluate the influence of the heat treatment temperature on both friction coefficient and wear resistance of a Ni-P-BN(h) composite coating with 33 vol% BN(h), thickness of 18.1 mu m and 5.5 wt% P deposited on a 316L stainless steel substrate. The as-deposited samples have been heat treated for Ih at 200, 300 and 400 degrees C in an argon atmosphere. X-ray diffraction analysis was employed in order to study the phase transformation produced during heating. The tribological behavior of the coatings under non-lubricated conditions has been studied by means of a pin-on-disc test. Microhardnesses of the coatings with and without heat treatment are also reported. It has been shown that the Ni-P-BN(h) composite autocatalytic coatings heat treated at 400 degrees C, which had the highest hardness, exhibit the lowest wear factor of 4.87 x 10(-7) mm(3)(N m)(-1) and this value is nearly one order of magnitude smaller than for all the other Ni-P-BN(h) composite coatings analyzed in this study. Due to the lubricating action of BN(h), the wear coefficient, k, was found to be two orders of magnitude smaller than the wear factor of 5.12 x 10(-5) mm(3)(N m)(-1) reported for a conventional Ni-P autocatalytic coating which has been heat treated at the same temperature of 400 degrees C. It was determined that the wear mechanism involved in the wear of the Ni-P-BN(h) composite was pure adhesive. (C) 1999 Published by Elsevier Science S.A. All rights reserved.