Ni－Nb合金在600～800℃低压氧中的氧化

THE OXIDATION OF Ni-Nb ALLOYS AT LOW OXYGEN PRESSURES AT 600-800℃

藉Ｈ２—ＣＯ２混合气体获得低氧压，在６００℃为１．０１×１０（－４）ｆＰａ，而７００℃与８００℃为１．０１ｆＰａ，并研究含Ｎｂ为１５０与３００ｍｇ／ｇ的两种Ｎｉ－Ｎｂ合金在上述条件下的氧化行为实验结果显示，在６００℃与７００℃，两种合金仅发生内氧化，其组成为α－Ｎｉ与氧化铌（Ｎｂ＿２Ｏ＿５或／和ＮｂＯ＿２）通常，在紧挨内氧化带前沿的合金中并没有观察到发生贫Ｎｂ现象．与之不同，在８００℃氧化的两种合金均产生连续的由氧化铌组成的外氧化膜而没有内氧化现象．从Ｎｂ在Ｎｉ中低溶解度的特点出发讨论了合金的氧化机制．

The oxidation of two Ni-Nb alloys containing 150 and 300 mg / g Nb has been studied at 600 -800℃ in H2 mixture providing an oxygen pressure of 1.01×10￣(-4)fPa at 600℃ and 1 .01 fPa O2 at 700 and 800℃,which are always below the dissociation pressure of Ni oxide. The scale formed on both alloys at 600 and 700℃ show only a region of internal oxidation composed of a mixture of a-Ni and Nb2O5 or NbO2,which formed from both the metal phases present, i.e.Ni8Nb and Ni3Nb. Only small or even no Nb depletion was observed in the alloys close to the front of the internal oxidation zone at these temperatures. On the contrary,samples of both alloys oxidized at 800℃ produced a continuous external scale of niobium oxides without internal oxidation.The oxidation mechanism of these alloys is examined with special reference to the effect of the low solubility of Nb in Ni.