喷涂工艺对Ta2O5原位复合钽基纳米晶涂层微观结构及摩擦磨损性能的影响

采用大气等离子喷涂制备了Ta₂O₅原位复合钽基纳米晶涂层,利用SEM、微束XRD、微动摩擦磨损实验机及非接触三维表面轮廓仪等技术手段并结合计算分析,考察了喷涂功率、主气(Ar)流量等对钽基涂层表面Ta₂O₅含量、晶粒尺寸、显微硬度和摩擦磨损性能等的影响规律及原因。在考察范围内,随喷涂功率增大,钽基涂层表面Ta₂O₅含量呈先减小后增大的变化,而涂层表面α-Ta的晶粒尺寸及点阵畸变则均呈先增大后减小的变化;随Ar气流量增大,涂层表面Ta₂O₅含量总体呈减小趋势,在流量为2.17×10^-3~2.33×10^-3m³/s时达到最低,α-Ta的晶粒尺寸与点阵畸变的变化呈负相关性;采用间断喷涂方法时涂层表面Ta₂O₅含量降低,α-Ta晶粒尺寸及点阵畸变均略有减小。通过对喷涂相关微观过程特点的分析,对这些规律作了阐释。涂层的显微硬度与其表面Ta₂O₅含量相关,高硬度涂层的表面Ta₂O₅含量相对较低;干摩擦条件下晶粒较大、Ta₂O₅含量较少的涂层抵御硬质陶瓷低速刻划的能力较差;边界润滑状态下硬度较高的涂层表现出更优的抗磨减摩性能;采取间断喷涂可获得摩擦学性能最佳的涂层。钽基涂层的机械性能与其微观结构特征显著相关;除显微硬度外,涂层晶粒尺寸、点阵畸变及表面Ta₂O₅含量的相对值可用作质量控制的重要指标。

Effect of Spraying Process on Microstructure and Tribological Properties of Ta2O5 In Situ Composite Nanocrystalline Ta-Based Coatings

In the fields of aviation,aerospace,and military,Ta-based coatings are of wide prospects in applications owing to their remarkable characteristics.Compared with other preparation methods,plasma spraying has obvious technical advantages in preparing Ta-based coatings.In this work,Ta₂O₅in situ composite nanocrystalline Ta-based coatings via plasma spraying were fabricated.Effects of the sprayingpower,main gas(Ar)flow rate,and spraying mode on the fine surface microstructure and friction,as well as on the wear properties of Ta-based coatings,were investigated using several techniques.Such techniques included SEM,micro-beam XRD,fretting friction and wear test,and computational analysis.Moreover,related rules and causes were discussed.Results indicated that the Ta₂O₅content at the surface of Ta-based coatings initially decreased and then increased with an increase in the spraying power.Conversely,the crystal size and lattice distortion ofα-Ta at the coating surface initially increased and then decreased.With an increase in the Ar flow rate,the Ta₂O₅content decreased in general and reached the lowest value when the flow rate was 2.17×10-3-2.33×10-3 m3/s.A negative correlation between the variation of the crystal size and lattice distortion with Ar flow rate has been observed.The Ta₂O₅content,crystal size,and lattice distortion slightly decreased due to intermittent spraying.Moreover,a significant correlation between the Ta₂O₅content and coating microhardness was observed.Under dry friction,the wear rate is closely related to both the oxide content and crystal size.Low oxide content and large crystal size results in high wear rate.Under boundary lubrication,coatings with higher levels of hardness exhibit better anti-wear and friction-reducing performance in the same series of Ta-based coatings.The coating exhibiting the best tribological properties can be achieved via intermittent spraying.Mechanical properties of Ta-based coating are significantly correlated with their fine microstructure characteristics.Aside from microhardness,the grain size,lattice distortion,and oxide content of the coatings can be utilized as important indexes to control the coating quality.