Improving weldability of aged 25Cr-35Ni heat resistant steel/alloy 800 dissimilar welds

Dissimilar welding between the aged 25Cr-35Ni (wt-%) heat resistant steel and alloy 800 is not successful due to liquation cracking in the heat affected zone of the aged steel. Microstructures, mechanical properties and weldability of the dissimilar weld were characterised using SEM and Varestraint test. The effects of a preweld solution annealing, heat input, interpass temperature and type of filler metal were investigated. It was found that the most important step to improve weldability and to reduce cracking susceptibility was solution annealing. A suitable annealing treatment was then proposed. It was concluded that dissimilar welding of alloy 800 to the aged 25Cr-35Ni steel can be successfully carried out under the conditions of solution annealing, low heat input and low interpass temperature using Inconel 82 or 617 filler metals.