Ni_3Al基合金的初期氧化速率

用感量为２μｇ的Ｓｅｔａｒａｍ热天平研究了Ｎｉ３Ａｌ及Ｎｉ３Ａｌ－Ｃｒ基合金７００℃～１１００℃的初期氧化行为。Ｎｉ３Ａｌ合金在中温区（７０００℃～９００℃）的氧化，随温度升高初期氧化速率明显增加（氧化５ｍｉｎ），８００℃及９００℃氧化０．５ｈ后试样的氧化增重低于７００℃的。在温度低于９００℃时，Ｎｉ３Ａｌ－Ｃｒ基合金的氧化增重明显小于Ｎｉ３Ａｌ基合金；高于１０００℃时，其氧化增重明显大于Ｎｉ３Ａｌ基合金的。ＥＤＳ分析表明Ｎｉ３Ａｌ－Ｃｒ基合金表面不出现纯ＮｉＯ相的氧化物区。加Ｃｒ可降低Ｎｉ３Ａｌ的晶格常数，增加原子密堆度，从而阻碍Ｎｉ原子的扩散，降低合金的氧化速率。

AN INVESTIGATION ON INITIAL OXIDATION RATE OF Ni_3Al ALLOY

The initial oxidation behavior of Ni3Al and Ni3Al-Cr alloys at a temperature range of 700-1100℃ was investigated using Setaram thermal anaysis instrument with sensitivity of 2 ug. At 700-900℃, the oxidation of Ni3Al in the first 5 minutes was accelerated markedly with increasing temperature. The weight gains of Ni3Al after xoidation for 0.5h at 800℃ and 900℃ was lower than that at 700℃. Addition of chromium into Ni3Al significantly reduced the oxidation rate of the alloy below 900℃, but increased its oxidation rate above 1000℃. The oxide scale was examined by EDS. The results indicated that no plain NiO phase region was observed on the oxide scale of Ni3Al-Cr alloy. Cr addition might decrease the lattice parameters of Ni3Al, increase the packing density and reject the surface diffusion of Ni.