Ti6Al4V表面激光改性层重熔处理的微观组织特征及宽温域摩擦学性能研究

采用激光复合工程技术对Ti6Al4V基体表面进行强化耐磨处理，首先在Ti6Al4V合金表面进行激光氮化[Ti(N)]和氮氧化[Ti(N,O)]处理，然后在纯氩气气氛中分别对Ti(N)层和Ti(N,O)层进行激光重熔处理，制备了组织分布更为均匀的重熔氮化层[Re-Ti(N)]和重熔氮氧化层[Re-Ti(N,O)]. 组织结构分析揭示了Re-Ti(N)层主要由富氮αˊ-Ti和TiNx组成，而Re-Ti(N,O)层则主要由富氧αˊ-Ti和TiNxOy组成. 相对于Ti6Al4V基体，Re-Ti(N)层和Re-Ti(N,O)层的硬度、弹性模量和磨损量降低了2倍以上，然而激光复合处理前后材料均表现出较大的摩擦系数. 相对于Re-Ti(N)层，氧原子的加入，不仅能够有效细化组织和提升强韧度，而且显著抑制了摩擦界面的黏着磨损. 通过磨屑结构分析进一步验证了基体黏着磨损机制和重熔改性层磨粒磨损机制.

Surface strengthening and wear-resistant treatment was conducted on Ti6Al4V substrates using laser composite engineering technology. First, laser nitridation [Ti(N)] and laser oxynitridation [Ti(N,O)] were performed on the surface of Ti6Al4V alloy. Subsequently, the Ti(N) layer and Ti(N,O) layer were separately subjected to laser remelting treatment in a pure argon atmosphere, preparing remelted nitrided layer [Re-Ti(N)] and remelted oxynitrided layer [Re-Ti(N,O)] with more uniform microstructure. Microstructure analysis revealed that the Re-Ti(N) layer is mainly composed of nitrogen-rich αˊ-Ti and TiNx, while the Re-Ti(N,O) layer is mainly composed of oxygen-rich αˊ-Ti and TiNxOy. Compared with the Ti6Al4V substrate, the hardness, elastic modulus and wear loss of both the Re-Ti(N) layer and Re-Ti(N,O) layer decreased by more than two times; however, all materials before and after laser composite treatment exhibited relatively high friction coefficients. Compared with the Re-Ti(N) layer, the addition of oxygen atoms can not only effectively refine the microstructure and improve strength and toughness, but also significantly inhibit adhesive wear at the friction interface. The wear debris microstructure analysis further verified the adhesive wear mechanism of the substrate and the abrasive wear mechanism of the remelted modified layer.