铝化物涂层对T92钢高温力学性能的影响

Effect of aluminide coating on the mechanical properties of T92 steel

在高温下长时间暴露,钢材表面的铝化物涂层与母材间容易发生元素互扩散,对母材组织产生影响,进而影响母材的力学性能。为研究超超临界机组用T92钢表面铝化物涂层的高温强度特性,采用低温粉末包埋渗铝法在T92钢锅炉管内壁制备铝化物涂层,并在室温至625℃环境中进行拉伸试验以及在625℃环境中进行持久试验,结合扫描电镜(SEM)、金相显微镜(OM)观察及X射线衍射分析,研究铝化物涂层对T92钢基体拉伸性能与持久寿命影响行为。研究结果表明:低温粉末包埋渗铝可在T92锅炉管内壁制备厚度约30.4μm的双层结构铝化物涂层,各层结构连续均匀且组织稳定,与母材呈冶金结合;在室温至625℃拉伸过程中,涂层为柱状晶结构且表面发生皴裂;625℃长时持久蠕变过程中,Fe-Al涂层裂纹数量分布多,但裂纹深度浅,极少数裂纹向基体扩展;高应力状态下大应变导致涂层发生局部剥落。铝化物涂层经长时间蠕变形变,仍与T92钢基体呈良好的冶金结合。

It is known that the interdiffusion at the aluminide coating/matrix interface during the long time exposure at high temperature would change the microstructure of the matrix and deteriorate the mechanical properties of the matrix.To analyze the high temperature strength of aluminide coating on T92 steel for ultra-supercritical unit,aluminide coating is prepared on the inner wall of T92 steel boiler tube by low temperature powder embedding method,and the tensile test was carried out at room temperature to 625℃and the durability test was carried out at 625℃environment.The effect of aluminide coating on the tensile properties and durability life of T92 matrix are studied by combining scanning electron microscope(SEM),optical microscope(OM)and X-ray diffraction analysis(XRD).The results show that the aluminide coating prepared on the inner wall of T92 boiler tube by low temperature powder embedding aluminizing,which is metallurgically combined with the matrix,has a double-layer structure,and each layer is continuous and uniform.The total thickness of the prepared aluminide coating is about 30.4μm.The coating has columnar crystal structure and the surface is cracked in the room temperature is increased to 625℃.During the creep rupture process at 625℃environment,FeAl coating have many cracks,but the crack depth is shallow and very few cracks extend to the matrix.The coating peels off locally large strains under the high stress state.It can be concluded that even deforms of the aluminide coating occurred during the long-time creep process,it can still has good metallurgical bonding with T92 matrix.