铂含量对改性铝化物粘结层高温氧化和内应力的影响

研究镍基高温合金的热障涂层系统中不同铂含量的改性铝化物粘结层在1100℃空气中循环氧化和非连续氧化行为及生成的氧化铝层的内应力状态。发现在不同循环氧化条件下,铂铝粘结层表面都形成连续致密的α-Al2O3层,并且α-Al2O3具有相同的形态和相似的平均厚度。而在非连续氧化初期,Al2O3层热生长应力快速增大,在氧化至100h时内应力出现峰值。同时由于高含量铂促进Al元素的扩散从而改变了涂层力学性能,造成高含量铂涂层中表现较大的内应力,但铂含量不能影响Al2O3层中内应力曲线变化趋势。另外,低铂含量涂层γ′-Ni3Al多沿β-NiAl晶界生成,而高含量铂使涂层晶粒细化,导致γ′-Ni3Al相呈弥散分布生长,从而可以形成Al元素的"网"状快速扩散通道。

Effect of Pt Content on High Temperature Oxidation and Residual Stress of Pt-Modified Aluminide Bondcoatings

Cyclic and discontinuous high-temperature oxidation behavior and the residual stress of thermal growth oxide (TGO) of modified aluminide bond coating with different Pt contents in nickel base superalloys for TBC (thermal barrier coating) application were studied in air at 1100 °C. It was found that the continuous and compact α-Al_2O_3 layers formed over Pt modified aluminide bond coating in the process of the cyclic oxidation, and the two Pt-modified aluminide coatings with different Pt contents had similar morphology and thickness. Thermal growth stress of α-Al_2O_3 layers increased quickly during initial discontinuous oxidation and a peak value of the residual stress appeared when the coating oxidation was prolonged to 100 h; at the same time, the high content of Pt promoted the diffusion of element Al, resulting in changing the mechanical property of the coating, and exhibiting a relatively great residual stress in the coating with high content of Pt, but the high content of Pt had no influence upon the change trend of the residual stress curve of α-Al_2O_3 layers. In addition, γ′-Ni_3Al phase usually grew along β-NiAl grain boundary, while the high content of Pt would refine coating grains, resulting in γ′-Ni_3Al growth in the way of dispersion distribution, and thus a net-like high velocity diffusion channel for element Al would form.