(1. 兰州理工大学 有色金属先进加工与再利用国家重点实验室，兰州 730050；
2. 东方电气集团东方汽轮机有限公司，德阳 618000；
3. 白俄罗斯国立技术大学，明斯克 220013；
4. 超达阀门集团有限公司，温州 325105)
摘 要: 采用激光硬化、激光气体氮化法分别对Ti-6Al-4V合金进行表面改性，以改善其耐磨耐蚀性能。利用XRD、SEM、EDS分析改性层层深、微观结构、相组成和元素分布，显微硬度仪测试改性层截面深度方向硬度，往复摩擦试验及电化学腐蚀实验分别测试基体、改性层摩擦学性能和腐蚀行为。结果表明：激光气体氮化层的耐磨耐蚀性能优于硬化层的。激光功率为2000 W时，获得层深达910 μm、氮化物枝晶分布均匀且无裂纹的氮化层，氮化层由表层高氮浓度的TiN树枝晶、底部低氮浓度的Ti2N细枝晶、热影响区的α′-Ti(N)针状晶组成；表层硬度达970 HV0.5、热影响区硬度530~360 HV0.5。氮化层耐磨性能较硬化层和Ti-6Al-4V合金基体分别提高21%和55%；在3.5%NaCl溶液中氮化层与硬化层电流密度较基体降低1个数量级；氮化层腐蚀电位较硬化层和基体分别正移0.239 V和0.091 V，极化电阻分别提高1.9倍和65倍。
关键字: 激光气体氮化；Ti-6Al-4V合金；激光功率；摩擦学性能；腐蚀行为
（1. State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China;
2. Dongfang Electric Corporation Dongfang Turbine Co., Ltd., Deyang 618000, China;
3. Belarusian National Technical University, Minsk 220013, Belarus;
4. Chaoda Valve Group Co., Ltd., Wenzhou 325105, China）
Abstract:To improve its wear resistance and corrosion resistance, the laser hardening and laser gas nitriding methods were employed to in-situ synthesize a laser modified layer on the surface of Ti-6Al-4V alloy. In this study, layer depth, microstructure, phase composition and element distribution of the modified layers were analyzed by XRD, SEM and EDS, respectively. The microhardness in different depth of the modified layer was tested by a microhardness tester. And the tribological properties and corrosion behavior of Ti-6Al-4V substrate and the modified layers were analyzed by reciprocating friction test and electrochemical corrosion experiment. The results show that both the wear and corrosion resistant performances of the laser nitride layer are the best among Ti-6Al-4V substrate and the laser hardened layer. Under the 2000 W laser power, an optimal laser nitrided layer with uniformly distributed nitrides, free cracks and the maximum depth of 910 μm is in-site synthesized, and with the microstructures of high nitrogen concentration dendritic TiN and low nitrogen concentration fine dendritic Ti2N on the surface and bottom region respectively, and with acicular crystals α′-Ti(N) formed in the heat affected zone. The hardness near the laser nitrided layer surface is about 970 HV0.5, and reduces to 530-360 HV0.5 in the heat affected zone. The wear resistance of the laser nitrided layeris21% and 55% higher than that of the hardened layer andTi-6Al-4V substrate. In 3.5%NaCl solution, the current density of the nitride layer and the hardened layer are one order of magnitude lower than that of Ti-6Al-4V substrate. And compared with the hardened layer and Ti-6Al-4V substrate, the corrosion potential of the nitride layer moves positively by 0.239 V and 0.091V, and the polarization resistance increases 1.9 and 65 times, respectively.
Key words: laser gas nitriding; Ti-6Al-4V alloy; laser power; tribological properties; corrosion resistance
