Re扩散障厚度对铂改性铝化物涂层1200 ℃氧化行为影响

Effect of the Re Diffusion Barrier Thickness on the Oxidation Behavior of Platinum-Modified Aluminide Coatings at 1200 ℃

摘要:

铂改性铝化物（PtAl）涂层具有良好的抗高温氧化和抗热腐蚀综合性能，被广泛用于单晶航空发动机高温合金叶片的高温防护。添加扩散障可阻止高温合金中难熔元素(W,Mo)向外扩散，提高涂层/基体结构稳定性，以及PtAl涂层抗氧化和高温力学性能。为探究Re扩散障厚度对PtAl涂层性能的影响，采用电镀与高温低活性渗铝技术，在Ni₃Al基单晶高温合金表面制备了无Re扩散障和3种不同厚度Re扩散障的PtAl涂层，开展了1 200 °C恒温氧化实验，对比分析了PtAl涂层的抗高温氧化性能。利用场发射-扫描电镜、能谱仪和X射线衍射仪，对涂层微观组织结构和成分进行了详细表征，对其氧化行为及失效机制进行了深入探讨。研究表明，未添加Re扩散障的制备态PtAl涂层呈现双层结构，包括外层和互扩散区。添加Re扩散障后，PtAl涂层转变为3层结构，包括外层、扩散障层和互扩散区。添加了Re扩散障的PtAl涂层，经1 200 ℃氧化后涂层表面呈现出更少的剥落面积，氧化膜相对致密完整，表明Re扩散障的添加可以显著提升PtAl涂层的抗高温氧化性能。随着Re扩散障厚度的增加，涂层的氧化增重进一步降低；然而，当Re扩散障厚度超过一定程度后，涂层抗氧化性能的提升并不明显。其原因是过厚的电镀Ni-Re层在氧化过程中导致了Re扩散障致密度和连续性的下降，降低了扩散障对Al元素的阻扩散效果。本研究深入揭示了Re扩散障厚度对PtAl涂层抗氧化性能的影响机理，为含Re扩散障的PtAl涂层的设计提供了重要理论基础。

Abstract:

This study aims to explore the effect of Re diffusion barrier thickness on the properties of platinum-modified aluminide coatings. The high-temperature oxidation resistance of platinum-modified aluminide coatings with varying thicknesses of Re diffusion barriers was comparatively analyzed. Employing electroplating and high-temperature low-activity （HTLA） aluminizing techniques， platinum-modified aluminide coatings with and without Re diffusion barriers of three different thicknesses were prepared on the surface of Ni₃Al-based single crystal superalloys， and the isothermal oxidation experiments were conducted at 1 200 ℃. The microstructure and composition of the coated samples were thoroughly characterized using SEM， EDS and XRD， and the oxidation behavior and failure mechanisms of the coated samples were also extensively analyzed. The results found that after electroplating and aluminizing， the as-deposited platinum-modified aluminide coating without Re diffusion barriers exhibits a double-layer structure， including an outer zone and an interdiffusion zone. With the addition of Re diffusion barriers， the platinum modified aluminide coatings have three layers， including the outer zone， diffusion barrier layer and interdiffusion zone. The platinum-modified aluminide coatings with Re diffusion barrier have less peeling area as well as a relatively dense and compact oxide scale after oxidation at 1 200 ℃， indicating that the addition of Re diffusion barrier significantly improves the high-temperature oxidation resistance of platinum-modified aluminide coatings. As the thickness of the Re diffusion barrier increases， the oxidation weight gain of the coating is further reduced. However， when the thickness of the electroplating Ni-Re layer is beyond a certain level， the improvement in the coatings’ oxidation resistance is not pronounced due to the decreased density and continuity during oxidation， which in turns reduces the ability to prevent the interdiffusion of Al element. This research provides a profound insights into the influence mechanism of Re diffusion barrier thickness on the oxidation resistance of platinum-modified aluminide coatings， and offers a vital theoretical basis for the design of such coatings with Re diffusion barrier.