氧燃比对爆炸喷涂WC-12 Co涂层组织和力学性能的影响

目的提高直升机旋翼系统连接件的耐微动磨损疲劳寿命,解决传统镀铬工艺引起的环境污染问题。方法采用爆炸喷涂工艺,通过调节氧气和乙炔混合气体氧燃比,在35Ni4Cr2MoA高强合金钢基体上制备不同的WC-12Co涂层,研究氧燃比对涂层组成、结构和力学性能的影响规律。结果随着氧燃比的提高,涂层C含量逐渐降低,硬度、致密性、弹性模量和结合强度则先升后降。氧燃比低于1.1时,粒子飞行速度低和熔融不充分是涂层硬度和致密性下降的主要原因;氧燃比高于1.3时,爆炸焰流为氧化气氛,WC粒子的氧化和分解加剧了C元素的流失,使得涂层性能下降;氧燃比为1.2时,涂层无明显氧化和脱碳,截面维氏显微硬度(HV0.3)达到12.9 GPa,孔隙率为0.86%,与基材间的结合强度达到148 MPa。结论爆炸喷涂中高速飞行的粒子对35Ni4Cr2MoA高强合金钢基体具有一定的表面强化作用,喷丸试棒经爆炸喷涂工艺沉积WC-12Co涂层后,疲劳寿命提高107.4%。氧燃比对爆炸喷涂沉积WC-12Co涂层的组成、结构和力学性能影响较大,氧燃比为1.2时,涂层的综合力学性能最佳。

Effect of Oxygen-Fuel Ratio on the Microstructure and Mechanical Properties of WC-12Co Coating Deposited by Detonation Spraying Method

Objective To improve the fretting wear fatigue resistant life of the helicopter rotor system connector and solve the environmental pollution problem caused by the traditional chrome plating craft. Methods By optimizing the oxygen-fuel ratio of oxygen and acetylene mixture, WC-12Co coating with high hardness and dense structure was deposited on the 35Ni4Cr2MoA high-strength steel substrate using the detonation spraying method. Influence of oxygen-fuel ratio on the composition, structure and mechanical property of the coatings was researched. Results The results showed that the carbon content of the coating decreased with increasing oxygen-fuel ratio. With the increase of the oxygen-fuel ratio, the hardness, density, elasticity modulus and bonding strength of the coating first increased and then decreased. When the oxygen-fuel ratio was less than 1. 1, the coating hardness and density decreased mainly due to the lower flight speed and insufficient melting of particles. When the oxygen-fuel ratio was more than 1. 3, oxidation and decomposition of WC particles in the oxidizing atmosphere of the explosion flame flow exacerbated the loss of carbon element. When the oxygen-fuel ratio was 1. 2, the coating showed no significant oxidation and decar-burization. The section Vickers hardness HV0. 3 reached 12. 9 GPa and the porosity was 0. 86% . The bonding strength between the coating and the substrate reached 148 MPa. Conclusion The high-speed particles in the process of explosion spraying had a surface strengthening effect on the 35Ni4Cr2MoA high-strength alloy steel substrate. After deposited WC-12Co coating using detonation spraying, the fatigue life of shot-peened test rod could be enhanced by 107. 4% . The oxygen-fuel ratio had a significant effect on the composition, structure and mechanical property of the WC-12Co coating deposited using the detonation spraying method. When the oxygen-fuel ratio was 1. 2, the coating showed no significant oxidation and decarburization and had an optimal comprehensive mechanical property.