TC4合金表面TiB_(2)强化TiAl_(3)复合渗层的组织形成及耐磨性能

Microstructure Formation and Wear Resistance of TiB_(2)-strengthened TiAl_(3) Composite Coating on TC4 Alloy

目的在TC4钛合金表面制备扩散渗层以提高其耐磨性能。方法采用包埋渗的方法,首先对TC4合金样品进行950~1100℃下4~8 h渗B,然后再进行950~1100℃下4 h渗Al制备TiB_(2)强化TiAl_3复合渗层。通过分析复合渗层的组织结构、表面粗糙度、硬度和磨损率等,结合对包埋渗B和Al过程的热力学分析,阐明TiB_(2)强化TiAl_3复合渗层的组织形成机理和耐磨性能。结果采用包埋渗的方法,可在TC4钛合金表面制备厚度约37~108μm的TiB_(2)强化TiAl_3复合渗层,其表面粗糙度约为5.485~9.320μm。复合渗层由硼化物相和Ti-Al金属间化合物相组成,TiAl_3层为复合渗层的主体,硼化物主要分布在复合渗层的表层区域,形成TiB_(2)连续层或弥散分布于TiAl_3层最外部。通过调整渗Al的温度和时间可调控复合渗层中硼化物的形态和分布。室温干摩擦条件下,TiB_(2)强化TiAl_3复合渗层与GCr15对磨时磨损率最低为2.65×10^(–5) g/(N·m),较相应渗B层可最多降低约75.0%。结论可采用扩散渗的方法,在TC4钛合金表面实现TiB_(2)强化TiAl_3复合渗层的可控制备,复合渗层表现出了比渗B层更优异的耐磨性能。

This work aims to prepare diffusion coating on TC4 titanium alloy to improve its wear resistance.By using the method of pack cementation technique,TiB_(2)-strengthened TiAl_(3) composite coating was prepared through firstly depositing B at 950~1100℃for 4~8 h and then depositing Al at 950~1100℃for 4 h.X-ray diffraction(XRD),scanning electron microscope(SEM),energy dispersion spectrum(EDS)and wave dispersion spectrum(WDS)were used to analyze the morphology and structure of the coating.Based on the analysis results of microstructure,surface roughness,hardness and wear rate of the TiB_(2)-strengthened TiAl_(3) composite coating,combined with the thermodynamic analysis of B and Al deposition processes,the formation mechanism and wear resistance of the TiB_(2)-strengthened TiAl_(3) composite coating are clarified.The thickness of the TiB_(2)-strengthened TiAl_(3) composite coating is about 37~108μm and its surface roughness is about 5.485~9.320μm.The composite coating is composed of boride and Ti-Al intermetallic compounds.The TiAl_(3) layer is the main body of the TiB_(2)-strengthened TiAl_(3) composite coating,and boride phase is mainly distributed on the surface of the composite coating,forming TiB_(2) continuous layer or dispersing in the outermost part of the TiAl_(3) layer.The morphology and distribution of borides in the TiB_(2)-strengthened TiAl_(3) composite coating can be controlled by adjusting the deposition temperature and time of aluminizing.When abrading with GCr15 under the condition of dry friction at room temperature,the wear rate of the TiB_(2)-strengthened TiAl_(3) composite coating can be as low as 2.65×10^(-5) g/(N·m),which is reduced by 75.0%compared with the corresponding B deposition layer.The TiB_(2)-strengthened TiAl_(3) composite coating shows better wear resistance than that of the B deposition layer.