Properties for the electron beam welds and friction stir welds of 9Cr-1.5W-0.15Ta heat resistant steel

9Cr-1.5W-0.15Ta heat-resistant steel was subjected to electron beam welding and friction stir welding process tests, respectively. The effects of different welding methods on the microstructural characteristics and mechanical properties of the welds were studied. The results showed that the electron beam weld was composed of coarse dendritic lath martensite structure, and the precipitates at the austenite grain boundaries and interior were completely dissolved. However, the grain refinement and homogenous microstructure are observed in the friction stir weld. The M23C6 carbides at the grain boundaries were dissolved, while there was no significant change for these spherical MX phase in the grains interior. Due to the formation of a large number of lath martensite structure, the hardness of electron beam weld and friction stir weld is significantly higher than that of the base metal. Difference of welding process methods has a greater impact on the impact absorption energy of their welds: the impact toughness of the electron beam weld significantly reduces, and the impact absorption energy is only 12.2% of the base metal. The impact toughness of friction stir weld is better, and the impact absorption energy is about 90% of the base metal.