High temperature wear of an electroless Ni–P–BN (h) composite coating

The present study reports the results on the high temperature tribological behavior of a Ni–P–BN (h) autocatalytic coatings deposited on AISI 316L stainless steel discs. A ball-on-disc configuration was employed and 6 mm diameter alumina balls were used as static counterpart. The as-deposited samples were previously post heat-treated at 400 °C for 1 h and wear tested at temperatures of 25, 100, 200, 300 and 400 °C, respectively. Friction coefficients and wear constants are reported. Scanning electron microscopy was used to determine the morphology of the wear scars on both tribological pair. As the wear test temperature increases, the autocatalytic Ni–P–BN (h) coating exhibits a higher friction coefficient and lower wear resistance. A mild adhesive wear mechanism (adhesive ploughing) was found for the samples tested at room temperature, whereas for those tested at higher temperature a mixed adhesive and fatigue wear mechanism, accompanied by a large plastic deformation of coatings and high coating transfer to the ball were observed. The results obtained are indicating that tribological response of the composite system at high temperatures is related to the mechanical properties of the Ni matrix, i.e. to its behavior to withstand the applied stresses as the temperature increases, irrespective to the nature and properties of the co-deposited particles.