钛合金表面激光熔覆AlB_xCoCrNiTi高熵合金涂层的组织与性能

Microstructure and Properties of Laser Cladding AlB_xCoCrNiTi High-entropy Alloy Coating on Titanium Alloys

目的研究AlB_xCoCrNiTi(x=0、0.5、1)高熵合金涂层的组织及性能,提高钛合金表面硬度及耐磨性。方法采用激光熔覆技术在TC4钛合金表面制备出AlB_xCoCrNiTi高熵合金涂层,运用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、电子探针(EPMA)等材料分析手段,研究了B含量对高熵合金涂层形貌、组织结构、成分的影响,并采用维氏硬度计以及摩擦磨损试验检测了熔覆涂层的硬度和耐磨性能。结果高熵合金涂层与基体的整体结合形貌良好。未添加B的高熵合金涂层主要由BCC相和晶体结构类似(Co,Ni)Ti_2相组成。随着B的加入,高熵合金涂层的晶粒得到细化,BCC相含量增加,(Co,Ni)Ti_2相含量有所减少,且熔覆层原位生成了TiB_2硬质相,TiB_2硬质相含量随B含量的增加而增加。熔覆涂层的硬度和耐磨性与B含量呈正相关关系,AlB_1CoCrNiTi高熵合金涂层的平均显微硬度最大,为814HV,且AlB_1CoCrNiTi高熵合金涂层的磨损量最小,其耐磨性约为未添加B的高熵合金涂层的7倍。结论 B含量的增加,有助于改善AlB_xCoCrNiTi高熵合金涂层的摩擦学性能,AlB_xCoCrNiTi高熵合金涂层有效提高了钛合金表面的硬度及耐磨性能。

The work aims to improve surface hardness and wear resistance of titanium alloy by studying microstructure and properties of AlBxCoCrNiTi（x=0,0.5,1） high-entropy alloy. The AlBxCoCrNiTi high-entropy alloy coatings were prepared on the surface of TC4 titanium alloys by laser cladding. The effect of B content （atomic percentage） on coating morphology, micro- structure and composition of the high-entropy alloy coating were studiedwith scanning electron microscopy （SEM）, X-ray dif- fractometer （XRD） and electron probe micro-analyzer （EPMA）, respectively. In addition, hardness and wear resistance of the coatings were studied with vickers hardness tester and friction-wear test. The high-entropy alloy coatings and the substrate had good overall bonding morphology. The AlCoCrNiTi high-entropy alloy coatings without Bwere mainly composed of BCC phase and （Co,Ni）Ti2 phase. With the addition of B, grains of the coatingswere refined, BCC phase content increased while （Co,Ni）Ti2 phase content decreased. Moreover, TiB2 hard phase formedin-situ in the cladding layer and increased with the addi- tion of B. The hardness and wear resistance were proportional to B content.The AlB1CoCrNiTi high-entropy alloy coatings ex- hibited the highest average microhardness of up to 814HV, and it also showed excellent wear resistance, which was 7 times of that of the AlCoCrNiTi high-entropy alloy coatings without B. The increase of B content contributes to improvement of tribo- logical propertiesof the AlBxCoCrNiTi high-entropy alloy coatings, which effectively enhance the hardness and wear resistance of titanium alloy surface.