单晶Ni—6.0Al—6.5Ta—8.5Mo—6.5Cr合金的高温氧化及其氧化物分布特征

对单晶Ni-6.0Al-6.5Ta-8.5Mo-6.5Cr合金高温氧化后的组织结构进行了SEM观察，并用EDAX和X射线衍射对其氧化物进行分析，研究了合金氧化物的分布特征及其对持久性能的影响。结果表明：在大气环境的服股条件下无保护涂层合金的表层、次表层发生明显的氧化、内氧化现象；在氧化初期形成以Al为主的氧化物，在近表层处形成以Cr,Al和Ta为主的氧化物，在次表层形成的大颗粒内氧化物为α-Al2O3,Mo不参与合金的内、外氧化，近内氧化物处出现贫Al区，致使区为γ强化相消失；有保护涂层的单晶合金高温氧化后，贫Al区尺寸减小，区内无大尺寸内氧化物，因此使合金的持久性能明显提高。

HIGH TEMPERATURE OXIDATION AND OXIDES DISTRIBUTION CHARACTERISTICS OF Ni-6.0Al-6.5Ta-8.5Mo-6.5Cr SINGLE CRYSTAL ALLOY

The isothermal oxidation characteristics and their influence on mechanical properties of Ni-6.0Al-6.5 Ta-8.5 Mo-6. 5 Cr single crystal alloy were investigated by means of SEM and EDAX. Results show that the internal oxidation obviously occurred in sub-layer of the alloy uncoated during high temperature oxidation in air. The scale contains large amounts of Al which was easily peeled off in the initial stage of high temperature oxidation. Cr, Al and Ta were identified as the main components of the scale formed in the near surface layer of the alloy. The internal oxide particles , a-Al2O3, with larger sizes formed in the sublayer. No oxides of Mo was found in the alloy during high temperature oxidation. The poor Al areas appear in near internal oxides, which resulted in the disappearance of r' strengthening phase. When the samples were coated with Al, the size of the poor Al areas was obviously decreased, no larger size internal oxides were found, which improved obviously the stress rupture property of the single crystal samples investigated.