Microstructural analysis of microwave processed EWAC + Cr₃C₂ cladding on SS-304 substrate

Abstract

The surface layer of SS-304 substrate was modified by a composite cladding of EWAC + Cr3C2 (20%, 40%, & 60% by weight) powder performed by utilizing the concept of microwave hybrid heating technique. The experimental testing was carried out in a home microwave applicator with an Al2O3 shield. Claddings of around 1 mm thickness were produced by exposing materials to microwave irradiation at a frequency of 2.45 GHz and 900 W of power. The entire system was exposed to microwave environment for about 360 s. The microstructural findings showed that the clads were produced via efficient metallurgical bonding, which entailed melting of clad powder along with diffusion of the substrate surface layer. The clads showed hard carbides in a columnar dendritic structure surrounded by a softer nickel-iron based matrix. The XRD spectrum shows that the clad also contains solid solution of Fe/Ni, chromium carbide (Cr23C6 and Cr3C2) and various intermetallic phases like NiSi, Ni3Si, and FeNi3. The average Vickers microhardness of the microwave processed clads was observed to be 700 ± 31 HV for EWAC + 60% Cr3C2, 580 ± 28 HV for EWAC + 40% Cr3C2 and 460 ± 23 HV for EWAC + 20% Cr3C2 respectively. The observed microhardness for all cases was higher than the substrate microhardness (260 ± 5 HV), which indicates the usefulness of the cladding for wear resistance applications.