A novel approach to synthesize surface composite by in-situ grown VC reinforcement in steel matrix via TIG arcing

Abstract

Tungsten Inert Gas (TIG) arcing is a surface modification process and can be used for some specific applications. In the present work, in-situ grown vanadium carbide particle coating was manufactured by initially applying the coating of finely ground vanadium and graphite powder on the steel substrate and subsequently fused the mixture by TIG arcing. Various reactions occurring in the fusion zone and the formation of different phases were thermodynamically predicted and related to the experimental observations. The modified surface was found to be free from micro-cracks and porosity. Microstructural characterization of the modified layer was performed by different techniques like the field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) etc. The results showed that the microstructure of the modified surface was consisted of vanadium carbide particles formed in-situ within the martensite matrix developed due to rapid cooling during TIG arcing. Further, the shape and size of these particles were evaluated by carbon replica method and characterized in scanning transmission electron microscopy (STEM) imaging mode available in the HRTEM. STEM analysis shows the formation of micron size vanadium carbide particles in cuboidal and rod shape as well as fine nanoprecipitations in a cuboidal shape. A significant increase in hardness of the modified region was observed which can be due to the combined effect of in situ formation of fine vanadium carbide in the martensite matrix.