Nb元素对高熵合金涂层组织与力学性能的影响

Effect of Nb components on the microstructure and mechanical properties of high-entropy alloy coatings

利用激光熔覆技术在Q235基体表面制备CoCrFeNiTi_(0.8)Nb_(y)(y=_(0.25),0.5,_(0.75),1.0)涂层.采用光学显微镜、X射线衍射仪、扫描电子显微镜、能谱分析仪等方法分析涂层的相结构和微观组织等;用显微维氏硬度计、摩擦磨损试验机测试涂层的硬度与耐磨性能.结果表明,组织中呈现典型的树枝晶结构,加入Nb元素,涂层微观组织的尺寸减小,增加Nb元素含量时,高熵合金涂层的晶体结构由体心立方相(body-centered cubi,BCC)、少量的面心立方相(face-centered cubic,FCC)和Fe_(2)(Ti,Nb)型的Laves相组成;在细晶强化、固溶强化和第二相强化的共同作用下提高了涂层的显微硬度;中间相的存在一定程度上可以阻碍犁削切削过程的进行,进而提高了涂层的耐磨性能;CoCrFeNiTi_(0.8)Nb_(0.75)涂层的硬度和耐磨性最好,硬度为710 HV,约为基体的4倍,涂层的磨损量最小,磨痕较为平整.

CoCrFeNiTi_(0.8)Nb_(y)(y=_(0.25),0.5,_(0.75),1.0)coatings were prepared on the surface of Q235 steel using laser cladding.The phase structure and microstructure of the coatings were analyzed by optical microscope(OM),X-ray diffractometer(XRD),scanning electron microscope(SEM)and energy dispersive spectroscopy(EDS).The hardness and wear resistance of the coatings were tested by micro-Vickers hardness hardness tester and friction wear tester.The results show that the microstructure shows a typical dendritic crystal structure,and the addition of Nb elements decreases the size of the grains;by increasing the content of Nb elements,the crystal structure of the high-entropy alloy coatings consists of BCC phases,a small amount of FCC phases,and Fe_(2)(Ti,Nb)-type Laves phases;the microhardness of the coatings is improved by the combined effect of fine-grained reinforcement,solid solution strengthening,and the strengthening of the second phase;The presence of the intermediate phase can hinder the plough cutting process to a certain extent,which improves the wear resistance of the coating;CoCrFeNiTi_(0.8)Nb_(0.75) coating has the best hardness and wear resistance,the hardness of 710 HV,about 4 times that of the substrate,and the coating has the smallest amount of abrasion,and the abrasion marks are relatively flat.