EFFECTS OF HEAT TREATMENT ON TRIBOLOGICAL BEHAVIOR OF ELECTROLESS Ni–B COATING AT ELEVATED TEMPERATURES
Abstract
The present work investigates the effects of heat treatment on friction and wear behavior of electroless Ni–B coatings at elevated temperatures. Coating is deposited on AISI 1040 steel specimens and subjected to heat treatments at 350∘∘C, 400∘∘C and 450∘∘C. Coating characterization is done using scanning electron microscope, energy dispersive X-Ray analysis and X-Ray diffraction analysis. Improvement in microhardness is observed for the heat treated deposits. Further, the effect of heat treatment on the tribological behavior of the coatings at room temperature, 100∘∘C, 300∘∘C and 500∘∘C are analyzed on a pin-on-disc setup. Heat treatment at 350∘∘C causes a significant improvement in the tribological behavior at elevated temperatures. Higher heat treatment temperatures cause deterioration in the wear resistance and coefficient of friction. The wear mechanism at 100∘∘C is observed to be predominantly adhesive along with abrasion. While at 300∘∘C, abrasive wear is seen to be the governing wear phenomenon. Formation of mechanically mixed layers is noticed at both the test temperatures of 100∘∘C and 300∘∘C for the coatings heat treated at 400∘∘C and 450∘∘C test temperature. The predominant wear mechanisms at 500∘∘C are abrasive and fatigue for as-deposited and heat treated coatings, respectively.
