Study On Crack Of Ni₃Al Based High Temperature And Laser Weld Seam Microstructure And Performance

Ni3Al-base alloy is one of the important high temperature engineeringmaterials. MX246A alloy is a kind of matrix of Ni3Al Ni3Al-base alloy materials,weld repairing MX246A alloy castings appear in the hot cracks which lead towelding joint performance decline. So the hot cracks for MX246A weldingcasting become a problem to be solved in the connection and weld repairing.Firstly MX246A high temperature alloy in the process of laser weldingappeared three kinds of crack of microscopic mechanism which was studied.Solidification cracking in the weld pool is due to low melting point eutecticthings which are gathered in the grain boundaries form a kind of so-called"liquid film" during solidification, and in the influence of the welding stresssolidification cracking emerges. Liquefied crack is the main reason thatMX246A when mother material contains more alloy of low melting point whichenrichment in area of grain boundaries nearly seam, and form liquid crystal, andin welding process at the end of the shrinking stress produces liquefaction crackin heat affected zone. Strain aging cracks are relevant to MX246A hightemperature alloy precipitation sclerosis and MX246A alloy key element of easyto form low melting point eutectic elements.Second in experiment it realizes MX246alloy welding of no crack by thelaser double sides welding method, and the MX246A alloy laser weldingorganization and performance of the double are studied. The quality of productsand performance mainly depend on the proportion of columnar crystal area andequiaxial crystal and grain size. With the increasing of the laser power, in seamorganization the number of columnar crystal is less and less, and the number of equiaxial crystal is more and more, and grain degrees more and more small, theorganization more density, the better mechanical properties. After the doublesides welding, it is tested by the high temperature and room temperature intensile test, and tests microhardness. The results show that the double weldingstretching and microhardness are better than the mother material.