Tribological and Corrosion behavior of HVOF Sprayed WC-Co, NiCrBSi and Cr3C2-NiCr Coatings and analysis using Design of Experiments

Abstract

This paper contributes to the evaluation of wear and corrosion resistance of the three types thermally sprayed cermet coatings deposited by High Velocity Oxygen Fuel (HVOF) spraying. In this paper, three different commercial powders agglomerated and sintered WC-12%Co, Cr3C2-25%NiCr (80-20) and gas atomized NiCrBSi a self fluxing alloy were thermally sprayed to deposit coatings onto mild steel substrates. The tribological tests concerned with the sliding wear behavior of the coated samples were performed using Pin on Disk apparatus and were analysed by Response Surface Methodology (RSM). To develop a wear model of coatings three factors temperature, load, sliding distance were used. ANOVA was carried out to determine the significant factors and interactions.The wear resistance of these coatings at room temperature and at 3500C were compared. The corrosion test was performed for which the specimens were tested in 3.5%Nacl aqueous solution with PH adjusted to 10 by adding potassium hydroxide and the polarization curves were obtained using the Potentiodynamic polarization system of GILL AC units. The property of the coatings such as adhesion was measured with the pull-off test method according toASTMC-633-01 standard, micro hardness. Deposition morphology and microstructure of coatings were studied using optical and electron microscopy. These measured mechanical properties were discussed with the microstructures of the coatings using electron microscopy, EDAX and X-ray diffraction. NiCrBSi is the best wear and corrosion resistant at room temperatures and WC-Co is best at a temperature of 3500C.