Preparation And High Temperature Oxidation Property Of Solid-liquid Doped La-TZM Alloy

TZM alloy(0.4%~0.55%Ti,0.06%~0.12%Zr,0.01%~0.04%C) is one of the most widely applied molybdenum alloy. TZM alloy has high melting point, high strength, high elastic modulus, good corrosion resistance and good mechanics performance. They are widely used in aerospace, power generation, nuclear and fusion reactors, military, industrial and chemical applications, where these alloys are subjected to high temperatures, liquid metal corrosion and other aggressive environments. However, poor high temperature oxidation resistance in the presence of air and poor plasticity have restricted TZM alloys practical applications.Doping powder metallurgy method, solid-liquid doping mode and particle grade mode were used to prepare high density La-TZM alloy plate(doped with lanthanum). The mechanical properties of lanthanum doped La-TZM alloy was studied through the tensile and the ductile brittle transition temperature(DBTT) test. After high temperature treatment of the traditional TZM alloy and La-TZM alloy samples at different times and temperatures, scanning electron microscopy and energy dispersive spectra analysis of the sample surface and cross-sections were performed to observed the microstructure and composition changes. Differential thermal analysis of the traditional TZM alloy and La-TZM alloy specimens after high temperature treatment were performed to assess the high temperature oxidation resistance of the coated matrix alloy. The results show that due to the doping of lanthanum, the tensile strength and elongation of TZM alloy increased by 28.2% and 32.8% respectively. And then, the DBTT of TZM alloy reduced about 40 oC by doping of lanthanum. Besides, lanthanum doped TZM alloy has more compact organization due to the effects of tiny lanthanum oxide particles. Alloy oxide generated will be formed in the dense oxide layer on the substrate surface, which can effectively block the invasion of oxygen to the matrix and the violent reaction with oxygen has been delayed about 50 oC, causing the improvement of the La-TZM alloy’s oxidation resistance.