An investigation on D-gun sprayed Al2O3-SiC coatings

Abstract

Mechanically blended Al2O3-SiC feedstock powder with varying SiC content (0%, 3%, 5%, 7%) is deposited on AISI 1020 steel substrates by Detonation gun technique. All the coatings are successfully deposited on the substrate without decomposing SiC in the coating. The influence of SiC content on the mechanical properties of the coating is thoroughly studied. Through XRD analysis and scanning electron microscopy (SEM) the phases and micro-structure of the coating are studied respectively. Quantitative phase analysis is performed by Rietveld refinement technique. Porosity of the coatings is estimated by image analysis technique. The wear behaviour of the coating is judged by ball-on-disc type tribometer. The micro-hardness and fracture toughness of the coatings are evaluated by using Vickers micro-hardness tester and scratch tester respectively. Among the four different coatings, Al2O3–3 wt% SiC coating is found to have the highest fracture toughness and micro-hardness values along with minimum porosity. Also, compared to the other three coatings Al2O3–3 wt% SiC has shown the highest wear resistant property. Adhesion induced spallation and brittle fracturing of lamellae are the two main wear mechanisms of the coatings. Phase stabilization of Al2O3 is found to happen while spraying with 3–5 wt% of SiC.