Cladding of Tribaloy T400 on steel substrates using a high power Nd:YAG laser

Abstract

Tribaloy T-400 is a cobalt based alloy with molybdenum additions, which has been developed for improved resistance to high temperature wear, galling and corrosion. Its hardness is provided by a hard intermetallic Laves phase, dispersed in a tough matrix of cobalt rich eutectic or solid solution. However, cracking limits its applications such as hard facing using laser surface cladding/coating. The primary aim of this work is accomplished by cladding crack free Tribaloy T-400 layer using a high power Nd:YAG laser. The optimal process conditions of cladding crack free Tribaloy T-400 coating on different steel substrates were obtained. The effects of iron dilution on the hardness of cladded Tribaloy T-400 coating are investigated. Dilution determined from clad geometry is verified from dilution calculated from an analysis of the composition of the clad. Microstructures of clad layers produced using optimal process parameters with and without preheating the substrate were analysed by Scanning Electron Microscopy (SEM). The chemical compositions of different phases present in the clad were analysed by Energy Dispersive X-ray Spectroscopy (EDS). Presence of phases with FCC and BCC structures and Laves phase (Co3.6Mo2Si0.4) in the clad were identified and analysed by X-ray Diffraction (XRD). The residual stresses in the clads were evaluated using hole drilling technique. The correlation between the process conditions and the resulting microstructures are discussed. Based on the results of this research, further scaling up to industrial application of laser cladding of Tribaloy T-400 is promising.