Ni掺杂对TiB_(2)硬质涂层组织结构和力学性能的影响

Influence of Ni Doping on the Microstructure and Mechanical Properties of TiB2 Hard Coatings

TiB_(2)涂层独特的晶体结构和强共价键赋予其超高的硬度和化学稳定性,但也存在韧性差及膜基结合力较差的问题。结合高功率脉冲磁控溅射技术和射频磁控溅射技术制备了Ni掺杂的TiB_(2)涂层,采用SEM、EPMA、XRD、XPS、纳米压痕仪、划痕试验仪、高温摩擦磨损试验机对比研究了不同Ni含量的TiB_(2)⁃Ni涂层的微观形貌、化学成分、物相结构、力学性能、摩擦学性能等。结果表明:Ni掺杂的TiB_(2)⁃Ni涂层中,少量Ni元素固溶于TiB_(2)晶格,过量的Ni元素以金属相形式存在,在晶界处形成了纳米复合结构,限制了TiB_(2)晶粒的生长,导致涂层柱状晶细化和纳米化。Ni元素掺杂导致TiB_(2)涂层的硬度与弹性模量明显下降,膜基结合力和涂层韧性随着Ni元素含量的增加持续增加,涂层摩擦系数先降低后升高,磨损形貌显示为磨粒磨损和粘接磨损。TiB_(2)⁃Ni涂层通过生成Ni金属相,在裂纹扩展时发生形变,以吸收断裂能量来提高涂层韧性,Ni含量为4.9%(原子分数)的TiB_(2)⁃Ni涂层具有较好的硬度和韧性。

The unique crystalline structure and strong covalent bonding of TiB_(2)coating give it ultra⁃high hardness and chemical stability,but it also suffers from poor toughness and weak bonding with metal substrates.Herein,Ni⁃doped TiB_(2)coating was prepared by combining high⁃power pulse magnetron sputtering technology and radio frequency magnetron sputtering technology.Additionally,SEM,EPMA,XRD,XPS,nanoindentation instrument,scratch tester,high⁃temperature friction and wear testing machine were used to comparatively study the micromorphology,chemical composition,phase structure,mechanical properties,and tribological properties of TiB_(2)⁃Ni coatings with different Ni contents.Results showed that the Ni⁃doped TiB_(2)⁃Ni coating possessed a small amount of Ni element solidly dissolved in the TiB_(2)lattice,and the excess Ni element existed in the form of a metallic phase,forming a nanocomposite structure at the grain boundaries,which restricted the growth of TiB_(2)grains,and caused the refinement and nanometerization of the columnar grains of the coating.Besides,the Ni doping brought about a significant decrease in the hardness and elastic modulus of the TiB_(2)coatings.With the increase of the Ni content,the adhesion strength between the coating and the substrate and the toughness of coatings continuously increased,while the friction coefficient of the coating decreased first and then increased.Moreover,the wear morphology indicated the wear of the coating belonged to abrasive wear and adhesive wear.In conclusion,Ni doping improved the toughness of the TiB_(2)⁃Ni coatings by generating Ni metal phase in the grain boundaries,which could absorb the fracture energy through deformation during crack expansion.The TiB_(2)⁃Ni coating with a Ni content of 4.9%(atomic fraction)