Fe-Cr-Ni-Ti高温合金氧化动力学研究

研究了一种Fe-Cr-Ni-Ti铸造高温合金在700～300℃范围内10分钟～500小时的氧化动力学。氧化增重符合抛物线规律;氧化凹坑深度的发展符合直线规律。氧化激活能Q_(P1)=38kcal/mol,Q_(P2)=42kcal/mol。短时氧化膜富Fe、Ti、Cr,主要由Fe_2O_2、TiO_2和Cr_2O_2组成;长时间氧化层主要由NiTi O_3和Fe Cr_2 O_4组成。氧化过程中,阳离子空位相互结合形成空穴,穴长大连接成空穴带,它是氧化层剥落的裂纹源。不均匀氧化剥落凹坑是η-Ni_3Ti或γ′-Ni_2(Al、Ti)选择性氧化所致。较高的含Ti量阻碍Cr_2O_3的形成,促进了尖晶石类型氧化物的形成,使合金抗氧化性能下降。

AN INVESTIGATION OF THE OXIDATION DYNAMICS OF AN Fe-Cr-Ni-Ti SUPERALLOY

The oxidation kinetics of an Fe-Cr-Ni-Ti superalloy, containing 4.43at％ titanium was studied in air over the temperature range of 700～900℃ for period of 10 minutes to 500 hours. The weightgain due to oxidation obeyed the conventional parabolic lair and the values of activation energy were Qp_1=38 kcal/mol and Qp_2=42 kcaI/mol. The depth of penetrating pits obeyed linear iaw. AES/ESCA indicated the initial sclae was rich in Ti, Fe and Cr, Consiting mainly of Fe_2O_3, TiO, and Cr_2O_3. By X-ray analysis the long-term oxides were estimated to be NiTiO_3 and FeCr_2O_4. The cation vacanies generated in oxidition at the alloy-scale inteerface joined up to produce oracks and caused spalling. The selective oxidation of η-Ni_3Ti phases genrated random penetsrating pits. The higher titanium concentration obstructed the formation of Cr_2O_3 protective scale and promoted the formation of NiTiO_3, thus deteriorated the oxidation resistance