钛合金表面激光熔覆h-BN固体润滑涂层

Solid Self-lubricating Coatings on TC4 Titanium Alloy by Laser Cladding with h-BN

目的优化钛合金激光熔覆固体润滑涂层的熔覆工艺参数,提高钛合金表面耐磨性能。方法采用Nd∶YAG激光器,分别在高功率和低功率条件下,在TC4钛合金表面制备h-BN固体自润滑涂层。观察分析熔覆陶瓷层的宏观形貌、物相组成、显微组织和硬度,采用摩擦磨损试验仪对熔覆层的摩擦学性能进行研究。结果低激光功率下,熔覆材料上浮流失严重,熔覆层的相成分主要是Ti N,Ti B,Ti B2等硬质相,硬度较高,存在裂纹。高激光功率下,基材的熔化稀释较好地抑制了润滑相h-BN的上浮,减少了溅射损失,发生了包晶反应,生成了单质金属Ti,熔覆层硬度低,但摩擦磨损试验表明,涂层中润滑相h-BN含量的增加使得形成了更好的润滑膜,降低了摩擦系数。结论在输出电流400 A,脉宽5 ms,频率12Hz,扫描速度120 mm/min,搭接率50%∽60%的条件下进行激光熔覆,所得熔覆层的表面状态平整,耐摩擦性能最好。

Objective To optimize the process parameters for laser cladding of solid self-lubricating coatings on titanium alloy, and improve the surface wear resistance of titanium alloy. Methods Using the Nd： YAG laser, h-BN （ hexagonal boron nitride） solid self-lubricating coatings were prepared on the surface of TC4 titanium alloy under conditions of high power and low power, re-spectively. The macro morphology, layer phase composition, microstructure, hardness and wear resistance of the ceramic layer were analyzed, and the tribological property of the ceramic layer was studied using a friction and wear tester. Results At low laser power, there was severe floating loss of cladding material, and the phase composition of the cladding layer was mainly composed of TiN, TiB, TiB2 and other hard phase components, the hardness was relatively high, with the presence of cracks. At high laser power, melting of the substrate inhibited the floating of the lubricating phase h-BN, reducing the sputtering loss, and peritectic re-action occurred, generating elemental metal Ti, the hardness value of the cladding layer was low, but the friction and wear tests showed increased h-BN content in the lubricating phase led to better formation of lubricating coating, further reducing the friction＆amp;nbsp;coefficient. Conclusion Under the condition of output current 400 A, pulse width 5 ms, 12 Hz frequency, scanning speed 120 mm/min, overlapping rate 50% ∽60%, the surface state of the laser cladding coating obtained was smooth and flat, and the fric-tion resistance was the best.