Studies on dry sliding wear behaviour of advanced ceramic coatings on aisi 304 stainless steel substrate

Abstract

The present work focuses on the development of rare-earth based ceramic multi-layer thermal barrier coatings on AISI 304 stainless steel substrate by Air Plasma Spraying (APS) process. The aim of this present work is to study the dry sliding wear behaviour of rare-earth based ceramic multi-layer thermal barrier coatings. The thesis discusses on the development of Rare-Earth Zirconate (Re2Zr2O7) and Rare-Earth aluminate (ReAO3) i.e. Re = La, Gd, Nd, Y candidate materials for thermal barrier coatings. All such materials are synthesized by solid-state reaction technique using high-energy ball-milling process and subsequently followed by two different calcination techniques. The prepared materials are analyzed for their morphology and powder flowability characteristics in addition to the particle size and distribution. Fundamental analysis such as X-ray diffraction, functional groups and specific surface area are also carried out. Initially, uncoated AISI 304 stainless steel substrate was analyzed for their microstructure and composition (EDX). The surface hardness and surface roughness of the uncoated AISI 304 SS was investigated. Empirical relationship regression equation was derived using Response Surface Methodology (RSM) in order to study the effect of applied load, sliding velocity, sliding distance and temperature on the specific wear rate and Coefficient Of Friction (COF) of the uncoated AISI 304 SS against WC disc counter body using Pin-On- Disc wear testing apparatus. The results clearly indicate that the specific wear rate of the uncoated AISI 304 SS increased with increasing applied load, sliding velocity and temperature but it was also found that the specific wear rate decreased with increasing sliding distance. However, an optimum value of sliding distance for lowest specific wear rate was found to be 5000 m with specific wear rate value of 51.73 X 10-5 mm3 /N.m. In addition, the COF of the uncoated AISI 304 SS increased with increasing applied load, sliding velocity and sliding distance. As the