等离子喷涂NiCr/Cr_3C_2-hBN复合涂层的制备及摩擦性能研究

Preparation and Tribological Properties of Atmospheric Plasma-sprayed NiCr/Cr_3C_2-hBN Wear-resistant Coatings

目的加入h BN作为固体润滑剂,提高Ni Cr/Cr3C2复合涂层的摩擦性能。方法采用化工冶金包覆、喷雾造粒和固相合金化技术制备Ni Cr/Cr3C2-10%h BN复合粉体,再采用等离子喷涂技术制备复合涂层。通过扫描电子显微镜(SEM)、X射线衍射(XRD)和高温摩擦磨损试验等手段研究粉体和涂层的显微结构、物相组成以及室温至800℃的摩擦磨损性能,探讨Ni Cr/Cr3C2-10%h BN复合涂层在室温和400,800℃下的磨损机理。结果等离子喷涂Ni Cr/Cr3C2-10%h BN复合涂层呈典型的层状结构,涂层结合强度可达24 MPa,孔隙率为(8.47±0.5)%。涂层的摩擦系数和磨损率均随着温度的升高而先升高,后逐渐降低,400℃时最高,分别约为0.59和9.2×10-4mm3/(N·m),800℃时分别降至0.45和4.1×10-4mm3/(N·m)。高温下,h BN润滑膜和金属氧化物的形成是摩擦系数和磨损率降低的主要原因。室温下涂层的主要磨损机制是脆性断裂;400℃时,涂层的主要磨损机制是脆性断裂、塑形变形和轻微粘着磨损;800℃时,涂层的主要磨损机制是塑性变形、氧化、粘着磨损和涂层转移至对偶件。结论等离子喷涂Ni Cr/Cr3C2-10%h BN复合涂层在室温和高温下的润滑性能较好。

Objective To improve the tribological properties of the NiCr/Cr3 C2 composite coatings by adding hBN into the coat-ings as lubrication. Methods The NiCr/Cr3 C2-10%hBN composite powder was prepared by the technology of chemical and metal-lurgical coating, spray granulation and solid state alloying. The coating was prepared by atmospheric plasma-spray technology using the prepared powder. The microstructure, phase composition and tribological properties from room temperature to 800 ℃ of coating were studied by SEM, XED and high-temperature tribometer. The tribonlogical mechanism of the APS sprayed NiCr/Cr3 C2-10%hBN composite coatings were investigated at room temperature, 400 ℃ and 800 ℃. Results The NiCr/Cr3 C2-10%hBN composite coatings consisted of elongated lamellae and the tensile strength of the coating was 24 MPa. The porosity of the coating was （8. 47±0. 5）%. The friction coefficient and wear rate of the coating firstly increased and then decreased with the increasing of tempera-ture. The friction coefficient and wear rate of the coating were 0. 59 and 9. 2x10-4 mm3/（N·m） at 400 ℃, 0. 45 and 4. 1x10-4 mm3/（ N·m） at 800 ℃, respectively, which was due to the formation of hBN lubricant film and metallic oxide at high tempera-ture. The abrasive mechanism of the NiCr/Cr3 C2-10%hBN composite coatings was dominated by brittle crack at room temperature, mixed brittle crack, plastic deformation and mild adhensive wear at 400℃, and it was characterized by plastic deformation, oxida-tion, adhesive wear and as well as coating transfer to the coupled pin at 800 ℃. Conclusion The NiCr/Cr3 C2-10%hBN composite coating exhibited excellent wear-resistant performance at both low and high temperature.