DEVELOPMENT OF NON-COBALT BASE CLADDINGS FOR IMPROVING EROSION RESISTANCE USING LASER CLADDING PROCESS

Abstract

Austenitic stainless steels of the 300 series have been widely employed for manufacturing components for nuclear plants. These components are usually protected from wear by cobalt-based claddings (Stellite). Efforts have been made in this field to find alternative materials, mainly nickel alloys, with the same efficiency but less expensive and without the problems of radioactive contamination. The microstructure, hardness, erosion wear of Colmonoy-5, Colmonoy-6 and Stellite-6 laser claddings was investigated. The slurry erosion and cavitation erosion behavior of Colmonoy-5 and Stellite-6 claddings was investigated using slurry erosion pot tester, vibratory horn apparatus, and adhesive wear behavior of Colmonoy-6 claddings was investigated using pin-on-disc setup. Laser cladding of Colmonoy-5, Colmonoy-6 and Stellite-6 on AISI 304L, 316L stainless steel substrates were prepared using 5 kW continuous wave CO2 laser. Claddings were metallurgically bonded to the substrate. Microstructural analysis was performed using Scanning Electron Microscopy (SEM). Energy Dispersive X-Ray (EDAX) analysis was carried out to study dilution and compositional variation. The claddings showed fine dendritic structure with eutectic mixture in interdendritic region. The hardness of claddings was greater than substrate material. The Colmonoy-5 and Stellite-6 claddings were subjected to slurry erosion and cavitation erosion. It was demonstrated that the cladding samples had high erosion resistance. Several failure mechanisms such as local plastic deformation, craters, pits, ductile rupture were observed. Colmonoy-6 claddings were subjected to adhesive wear using pin-on-disc set up. Colmonoy-6 claddings tend to display oxidative wear behavior over a wider range of applied loads. Wear coefficients are greatly influenced by the type of wear, i.e. oxidative or metallic, which in turn is a function of the alloy composition, applied load and sliding velocity.