Microstructure and microhardness of Co-8.8Al-9.8W superalloy cladding layer with different boron content

TIG welding was used to deposit Co-8.8Al-9.8W-0.2B superalloy on304austenite stainless steel.The form factor of weld,dilution ratio,microhardness,microstructure and distribution of alloying elements were investigated.The microstructure of cladding layer was mainly hypoeutectic.The primary phases were cobalt-rich solid solution.The eutectic phase was composed of cobalt-rich solid solution,Co6 W6 C and CoCx.When the boron content increased from0.2%to0.5%,the dilution ratio decreased,the primary phase became coarse and the microhardness decreased.When the boron content was from0.5%to2%,the dilution ratio and microhardness increased obviously,but the primary phase was refined.The hard phase of Co-8.8Al-9.8W became refined and the amount was raised,and the performance of cladding layer was improved with appropriate boron increase.