(1. 蘭州理工大學 有色金屬先進加工與再利用國家重點實驗室，蘭州 730050；
2. 東方電氣集團 東方汽輪機有限公司，德陽 618000)
摘 要: 在用矩形光斑高功率半導體激光器，在純氮氣和氮氬混合兩種不同方式下，通過不同氣流量和氮氬混合對Ti-6Al-4V進行表面滲氮，研究氣體流量、氮氬混氣比對滲氮熔池形態(tài)及滲氮組織和力學性能的影響。采用SEM、EDS以及XRD對滲氮層的顯微組織、微區(qū)成分及相組成進行研究。結果表明：采用純氮滲氮時，在15 L/min氣流量下獲得均勻滲氮層，繼續(xù)增大氣流量滲氮熔池流動紊亂，出現(xiàn)貫穿裂紋，且滲氮深度和硬度并未隨氣流量增加；采用不同氮氬混氣比滲氮時，滲氮層的表層硬度均較相同條件下純氮氣滲氮層的有所降低，且滲氮層裂紋傾向減弱，滲氮層組織由表至里在200~800 μm內按層深依次存在TiN0.88、TiN0.61、TiN0.3三種穩(wěn)定相；分別采用純氮氣和不同氮氬混氣比滲氮時，滲氮層組織沿層深分布依次均為粗短樹枝晶、等軸晶、細長樹枝晶、針狀晶。
關鍵字: 激光滲氮；氣體流量；裂紋；組織
（1. State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China;
2. Dongfang Turbine Co., Ltd., Dongfang Electric Corporation, Deyang 618000, China）
Abstract:In two different ways of pure nitrogen and nitrogen argon mixing, a rectangular spot high-power semiconductor laser was used to nitride on surface of Ti-6Al-4V under different gas flow rates and nitrogen to argon mixture ratios. The effects of gas flow rates and gas mixture ratio of nitrogen to argon on nitriding molten pool morphology, nitriding microstructure and mechanical properties were studied. The microstructure, composition and phase composition of nitriding layer were studied by scanning electron microscopy(SEM), energy dispersion(EDS) and X-ray diffractometry(XRD). The results show that the uniform nitriding layer is obtained at pure nitrogen gas flow rate of 15 L/min. Continue to increase the gas flow, the flow of the nitriding molten pool is turbulent and the through cracks appear. The depth and hardness of the nitriding do not increase with the gas flow. When nitriding with different gas mixture ratios of nitrogen to argon, the surface hardness of the nitriding layer is lower than that of the nitriding layer at pure nitrogen nitriding, and the cracking tendency of the nitriding layer is weakened. The microstructure of the nitriding layer is three stable phases of TiN0.88, TiN0.61, TiN0.3 according to the layer depth in the range of 200 to 800 μm from the surface to the inner. Under pure nitrogen and different gas mixture ratios of nitrogen to argon for nitriding, the microstructure of nitriding layer is composed of coarse short dendrite, equiaxed grain, slender dendrite, fine needle-shaped grain, respectively.
Key words: laser nitriding; gas flow rate; cracks; microstructure
