(1. 蘭州理工大學(xué) 有色金屬先進(jìn)加工與再利用國家重點(diǎn)實(shí)驗(yàn)室，蘭州 730050；
2. 東方電氣集團(tuán)東方汽輪機(jī)有限公司，德陽 618000；
3. 白俄羅斯國立技術(shù)大學(xué)，明斯克 220013；
4. 超達(dá)閥門集團(tuán)有限公司，溫州 325105)
摘 要: 采用激光硬化、激光氣體氮化法分別對Ti-6Al-4V合金進(jìn)行表面改性，以改善其耐磨耐蝕性能。利用XRD、SEM、EDS分析改性層層深、微觀結(jié)構(gòu)、相組成和元素分布，顯微硬度儀測試改性層截面深度方向硬度，往復(fù)摩擦試驗(yàn)及電化學(xué)腐蝕實(shí)驗(yàn)分別測試基體、改性層摩擦學(xué)性能和腐蝕行為。結(jié)果表明：激光氣體氮化層的耐磨耐蝕性能優(yōu)于硬化層的。激光功率為2000 W時，獲得層深達(dá)910 μm、氮化物枝晶分布均勻且無裂紋的氮化層，氮化層由表層高氮濃度的TiN樹枝晶、底部低氮濃度的Ti2N細(xì)枝晶、熱影響區(qū)的α′-Ti(N)針狀晶組成；表層硬度達(dá)970 HV0.5、熱影響區(qū)硬度530~360 HV0.5。氮化層耐磨性能較硬化層和Ti-6Al-4V合金基體分別提高21%和55%；在3.5%NaCl溶液中氮化層與硬化層電流密度較基體降低1個數(shù)量級；氮化層腐蝕電位較硬化層和基體分別正移0.239 V和0.091 V，極化電阻分別提高1.9倍和65倍。
關(guān)鍵字: 激光氣體氮化；Ti-6Al-4V合金；激光功率；摩擦學(xué)性能；腐蝕行為
（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
