包埋渗结合激光熔覆制备复合涂层的高温抗氧化性

High Temperature Oxidation Resistance of Duplex Coatings Prepared by Pack Cementation Combined with Laser Cladding Technology

为了提高铌合金的抗氧化性能,采用铝硅共渗的方法在铌合金表面制备Al-Si涂层,结合激光熔覆技术于渗层上熔覆MOSi2涂层。探讨了Al-Si渗层的生长机制,研究了铌合金表面Al-Si渗层及MoSi2/Al-Si涂层的抗高温氧化性能。结果表明:Al-Si渗层的形成过程是源于Al、Si元素的先后沉积,优先形成了Al3Nb相。渗层厚度x与保温时间f遵循关系式:x=At1/2+7.4(1000℃:A=11.6,1050℃:A=16.2)。激光熔覆制备的MoSi2/Al-Si涂层均匀连续致密,与基体结合紧密,无裂纹孔洞等缺陷。主要相结构为MoSi2、Al3Nb、NbSi2、Nb5Si3和Mo(Si,Al)2。经1200℃氧化后,Al-Si渗层及MoSi2/Al-Si涂层都形成大量的SiO2保护膜,阻止了氧原子的进一步扩散。与Al-Si渗层相比,MoSi2层表面形成的连续致密混合氧化物有效避免了Al-Si渗层的快速消耗,MoSi2/Al-Si涂层的高温氧化优于Al-Si渗层。

In order to improve oxidation resistance of niobium alloy,an Al-Si coating was prepared on the surface of the niobium alloy by Al-Si co-deposition and then a MoSi2 coating was prepared continuously by laser cladding technique.The growth mechanism of the Al-Si co-deposition was investigated and the high-temperature oxidation resistance was discussed by comparing the Al-Si layer to the MoSi2/Al-Si coating.The results show that the formation process of the Al-Si coating is derived from the sequential deposition of A1 and Si elements,and Al3 Nb phase is preferentially formed.The thickness x and the holding time t follow the relationship:x=At1/2+7.4,where A=11.6 at 1000℃and A=16.2 at 1050℃.The MoSi2/Al-Si coating prepared by laser cladding is uniformly continuous and compact,which is tightly bound to the substrate without cracks and holes found.MoSi2,Al3 Nb,NbSi2,Nb5 Si3 and Mo(Si,Al)2 phases are detected in the as-deposited duplex coatings.After oxidation at 1200℃,a large amount of SiO2 are formed to prevent the inward diffusion of oxygen atoms on the Al-Si coating and the MoSi2/Al-Si coating.Compared with the Al-Si coating,presence of continuous oxide scales on the duplex coatings effectively avoids rapid consumption of the Al-Si layer,so that the MoSi2/Al-Si coating exhibit more excellent high temperature oxidation resistance.