Erosion performance of microwave processed nickel-base coatings at an elevated temperature

Abstract

Boiler components degrade through erosion wear during exposure to coal, fly ash, or other fuel constituents at different temperatures. At high temperatures, the boiler material loses its hardness, strength, and toughness, and fails due to erosion and oxidation; thus, suitable protective coatings need to be developed and investigated. Protective coatings/claddings of various material combinations are developed to preserve the preferred properties of the base material by shielding it. In this study, two nickel-based claddings [i.e., Ni-13(WC8Co2Cr) and Ni-6(WC8Co2Cr)] were developed on an AISI-316 stainless steel using a microwave hybrid heating technique, which is compatible with developing claddings of significantly higher microhardness than conventional processing techniques due to the formation of a strong dilution layer. Here, Nickel is used as a base material, which acts as a tough and ductile matrix at high temperatures and provides good bonding to the reinforcing phases. Cobalt is added to refine the microstructure and provide high hardness with harder Tungsten carbide constituents. Further, adding Chromium is expected to improve the performance of Nickel-base coatings at high temperatures against erosion, corrosion, oxidation and wear, while enhancing the hardness and strength. The erosion behaviors of the developed claddings were evaluated at room temperature and 700 °C. The Ni-13(WC8Co2Cr) cladding provided an exceptional erosion resistance compared to the Ni-6(WC8Co2Cr) cladding under all test conditions, attributable to its higher overall microhardness and the formation of a higher amount of harder Tungsten carbide and Cobalt tungsten carbide phases. The eroded surfaces were examined using a scanning electron microscope.