预先真空氧化处理对CoCrAlY耐高温腐蚀涂层表面热生长氧化层的影响（英文）

Effects of vacuum pre-oxidation process on thermally-grown oxides layer of CoCrAlY high temperature corrosion resistance coating

研究预先真空氧化处理工艺对耐高温涂层的热生长氧化物(TGO)相变的影响,用超音速火焰喷涂技术在镍基合金基底上喷涂CoCrAlY耐高温腐蚀涂层,然后对其进行特定的预先真空氧化处理。研究表明:未预先真空氧化处理试样在高温氧化初始阶段,TGO中除了含有Al2O3,还含有大量的Cr2O3、CoO和尖晶石类氧化物,而且Al2O3的形成量主要取决于氧分压。CoCr2O4尖晶石的形成阶段主要在高温氧化的初始高氧分压阶段和随高温氧化进行的化学反应阶段。经过适当的预先真空氧化处理后,TGO的主要成分为低Y含量的Al2O3,零星分布着高Y含量的Al2O3,未观察到明显的大晶粒尖晶石结构氧化物;随着高温氧化时间的延长,少量多孔状的CoCr2O4尖晶石和Cr2O3零星分布于连续的Al2O3周围。另外,TGO的生长率比未预先真空氧化处理的低。

The influence of the certain specific vacuum pre-oxidation process on the phase transformation of thermally-grown oxides（TGO） was studied.The CoCrAlY high temperature corrosion resistance coatings were produced onto the nickel-based superalloy substrate by high velocity oxygen fuel（HVOF）.It suggests that the TGO usually consists of a great number of chromium oxides,cobalt oxides and spinel oxides besides alumina during the initial period of the high temperature oxidation if the specimens are not subjected to the appropriate vacuum pre-oxidation process.Furthermore,the amount of alumina is strongly dependent on the partial pressure of oxygen;while the CoCr2O4 spinel oxides are usually formed under the conditions of higher partial pressure of oxygen during the initial period and the lower partial pressure of oxygen during the subsequent period of the isothermal oxidation.After the appropriate vacuum pre-oxidation process,the TGO is mainly composed of alumina that contains lower Y element,while alumina that contains higher Y element sporadically distributes,and the spinel oxides cannot be found.After a longer period of the isothermal oxidation,a small amount of porous CoCr2O4 and the chrome oxide sporadically distribute near the continuous alumina.Additionally,after the appropriate vacuum pre-oxidation process,the TGO growth rate is relatively slow.