Duplex electroless Ni-P/Ni-P-W coatings: Effect of heat treatment on tribological and corrosion performance

The current study attempts to investigate the effect of heat treatment on duplex electroless Ni-P/Ni-W-P coatings. Duplex electroless Ni-P/Ni-W-P coatings are produced on mild steel and heat-treated for 2 h at temperatures ranging from 200 to 800 ?. A pin-on-disc arrangement is used to test the friction and wear characteristics of the as deposited and heat-treated coatings. The microstructural aspects are studied, viz. surface morphology, composition and the crystallographic structure. Heat-treatment at 400 ? for a two-hour duration produces the maximum hardness due to the formation of the crystalline nickel phosphide (Ni3P) phase. The friction and wear performance of the coating seems to be diminishing at higher temperatures due to the formation of oxides and grain coarsening. Corrosion tests on duplex coatings reveal better corrosion resistance for coating with Ni-W-P as the outer layer. Copyright (C) 2022 Elsevier Ltd. All rights reserved.