Microstructure and mechanical properties of TiB2–TiC–Al2O3–SiC composite coatings developed by combined SHS, sol–gel and laser technology

Abstract

A ceramic matrix composite (CMC) coating with a novel composition (TiB2–TiC–Al2O3–SiC) is developed by combining SHS (self-propagating high temperature synthesis), Sol–gel and laser technology. TiO2 and SiO2, were obtained as nano-particulate powders from Sol–gel technology. Multiple SHS reactions are laser-triggered in a mixture of aluminum (Al), boron carbide (B4C) and graphite (C) powders and sol–gel derived nano-particulate titanium oxide (TiO2) and silicon oxide (SiO2) powders, to yield hard ceramic phases that are subsequently laser clad onto substrates, namely AISI 1020 steel and AISI 304 steel. Varying amounts of (SiO2 + C) are added with a fixed ratio of TiO2, Al and B4C to observe the effect of additional SiC on the properties of TiB2–TiC–Al2O3–SiC composite. The developed coatings exhibit appreciable increase in hardness, wear resistance and coefficient of friction (COF) with increase in proportion of (SiO2 + C) in the precursor powder mixture.