Erosion wear characteristics of HVOF Sprayed WC-Co-Cr and CoNiCrAlY coatings on IS-2062 structural steel

Structural steel components of thermal power plants are exposed to the oxidative and erosive environment during the operation of the plants. Such steels have good structural properties but lack resistance to erosion. Hard coatings are deposited on structural steels to improve their erosion resistance while maintaining good structural properties. The current work emphasizes the role of HVOF sprayed WC-12Co-4Cr and Co-32-Ni-21Cr-8Al-0.5Y coatings on the erosive wear of IS-2062 structural steel. Coatings are evaluated in terms of hardness, erosion rate, adhesion to the substrate, surface roughness and porosity. The erosion tests are carried out using an air jet erosion tester at 30° and 90° impact angles under room temperature environment. From this investigation, it has been observed that WC-Co-Cr coating on IS-2062 structural steel provides better erosion resistance than Co-32-Ni-21Cr-8Al-0.5Y coating at both the impact angles. However, the higher erosion rate is found at 90° impact angle than that at 30° impact angle for both the coatings suggesting a dominating brittle erosion mechanism. Microhardness and surface roughness of the coatings played an important role in the erosion resistance of WC-Co-Cr and CoNiCrAlY coatings. (paper)