Effect of WC Addition in Ni-Cr Matrix on Performance as Coatings for Corrosion/Erosion Protection of Heat Exchanger Materials

Abstract

Fireside corrosion and erosion of heat exchanger tubes is a serious problem. One of the methods to combat this is by applying corrosion and erosion resistant coatings. Nickel– chromium alloys have already been used as coatings to deal with oxidation environments at high temperature. The wear resistance of these coatings can be improved by adding different hard precipitates such as carbides of refractory metals and cemented carbides. In the present study, various compositions comprising of Ni-Cr with 15, 35, 60 and 100% wt% WC/Co were made using thermal spray grade powders. These were then coated on steel substrate by the HVOF method. After detailed characterization of the coatings, the performance of the coatings at high temperature was studied by exposing the coated samples in the temperature range of 600-700°C. Ni-alloy coatings with moderately (15%) added WC/Co showed better oxidation resistance than coatings with high percentage of WC/Co and also than the pure Ni-alloy coating in high temperature range of 600-800°C. From the characterization, it was found that Ni-Cr alloy with 15% WC/Co gave the optimum results.