Erosive wear of a surface coated hydroturbine steel

In the present investigation, stellite-6, Cr3C2-NiCr and WC-Co-Cr coatings were deposited by D-Gun on a hot rolled 21Cr-4Ni-N steel meant for fabrication of hydro turbine underwater parts. The coatings have been characterized for microstructure, porosity, microhardness and crystalline nature. The erosion experiments were carried out using an air jet erosion test rig at a velocity of 120 ms(-1) and impingement angles of 30A degrees and 90A degrees. Silicon carbide particles of size ranging between 500 and 700 mu m were used as erodent. Scanning electron microscopy (SEM) technique was used to analyse the nature and mechanism of erosion. Erosion behaviour is observed to be influenced largely by the nature and extent of porosity in the surface coatings.