Research Of GTAW Repairing On Runner Vane-type Parts Of Different Materials

Gas tungsten arc welding (GTAW) repairing technology, is a kind of "greenremanufacturing" technology which has a broad application value, can not only greatlyimprove the yield of castings which is saving substantial economic cost, but also greatlyreduce the time and economic costs caused by component failure. While runner vane-typeparts not only have low yield of manufacturing and processing due to its complex surfacestructure and uneven thickness; but also develop cavitations and easy to wear, cracking andother problems during its operation. So for the sake of practical application needs, researchon GTAW repair techniques for runner vane-type parts of two different materials:20SiMnand K423A. With the help of optical microscope, SEM, EDS and XRD, microstructure ofwelding joints was observed and analyzed, so its micro hardness was tested. And therecomes the following conclusions:It does well using GTAW welding repair on vanes which are made of20SiMnmaterial, which can significantly reduce the cracks. However, the welding joints are proneto generate hardening martensite in the heat-affected zone, increasing the joint crackingtendencies. There can generate minimal martensite in HAZ using80A welding current withpreheated treatment, and it can significantly reduce the heat-affected zone martensite withpost-weld heat treatment by high-temperature tempering, which improves the weldingjoints’ microstructure and hardness.While there are prone to generate cracks and other defects either welding or post-weldstress relieving heat treatment using GTAW welding repair on K423A material vanes. Butresearch results are: it is feasible to repair K423A superalloy by using GTAW thoughK423A has poor weldability from following aspects: the use of non-aluminum titaniumwire, set appropriate shielding gas flow parameters with front and back gas protectionwhile welding, develop appropriate welding current according to the thickness of thesample to be welding, adopt the principle of " improving the welding joints’ microstructurefirst, conducting stress relieving treatment second" to do post-weld heat treatment, andmoreover obtain welding specifications of GTAW welding repairing K423A superalloy.