Metallurgical Study of Stellite 6 Cladding on 309-16L Stainless Steel

Abstract

309-16L stainless steel was deposited over base metal Grade 91 steel (9Cr–1Mo) as buffer layer by shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW) and flux cored arc welding processes, and then, Stellite 6 (Co–Cr alloy) was coated on stainless steel buffer by SMAW, GTAW and plasma transferred arc welding processes. Stellite 6 coatings were characterized using optical microscope, Vickers hardness tester and optical emission spectrometer, respectively. The FCA deposit has less heat-affected zone and uniform hardness than SMA and GTA deposits. The buffer layer has reduced the formation of any surface cracks and delamination near the fusion zones. The microstructure of Stellite 6 consists of dendrites of Co solid solution and carbides secretion in the interdendrites of Co and Cr matrix. Electron-dispersive spectroscopy line scan has been conducted to analyse the impact of alloying elements in the fusion line and Stellite 6 deposits. It was observed that dilution of Fe in PTA-deposited Stellite 6 was lesser than SMA and GTA deposits and uniform hardness of 600–650 \(\hbox {HV}_{0.3}\) was obtained from PTA deposit. The chemical analysis resulted in alloy composition of PTA deposit has nominal percentage in comparison with consumable composition while GTA and SMA deposits has high dilution of Fe and Ni.