Investigating the effect of CMT (Cold Metal Transfer) process on dilution of the Stellite 6 overlay

CMT process is a new developed gas metal arc welding (GMAW) process which has low dilution and heat input. This method is useful for expensive electrodes which are used in surfacing. In this research 1, 2 and 3 layer of flux cored Stellite 6 is deposited on A516-Grade 70. Same type of this steel with hard faced Stellite 6 is widely used in oil, gas and petrochemical industries especially where there is a need for wear and oxidation resistance at high temperatures. Chemical composition of layers is explored and the changes in dilution and iron content versus layer number and final thickness of deposited weld are investigated. Similar samples were prepared with conventional GMAW process for comparison. The results showed that heat affected zone (HAZ) in CMT samples are thinner and reduces by 28% which means less heat input in this process. In CMT process Dilution and weld penetration are 39% and 41% respectively less than conventional welding process. By using this method, the desired chemical composition is achievable with less number of thinner layers and leads to reduction of welding electrode consummation