曹丽琴,孙利娜,轩福贞,王正东.激光辅助氮化工艺中的开裂行为研究[J].表面技术,2013,42(6):1-5,36.
CAO Li-qin,SUN Li-na,XUAN Fu-zhen,WANG Zheng-dong.Experimental Study on the Cracking Behavior in Laser-assisted Nitriding Process[J].Surface Technology,2013,42(6):1-5,36
激光辅助氮化工艺中的开裂行为研究
Experimental Study on the Cracking Behavior in Laser-assisted Nitriding Process
投稿时间:2013-07-10  修订日期:2013-08-16
DOI:
中文关键词:  激光氮化  显微组织  裂纹  应力
英文关键词:laser nitriding  microstructure  cracking  stress
基金项目:国家自然科学基金(11247236) ;河北省高等学校科学技术研究指导项目( Z2011120)
作者单位
曹丽琴 燕山大学, 秦皇岛 066004;华东理工大学, 上海 200237 
孙利娜 燕山大学, 秦皇岛 066004 
轩福贞 华东理工大学, 上海 200237 
王正东 华东理工大学, 上海 200237 
AuthorInstitution
CAO Li-qin Yanshan University, Qinhuangdao 066004, China;East China University of Science and Technology, Shanghai 200237, China 
SUN Li-na Yanshan University, Qinhuangdao 066004, China 
XUAN Fu-zhen East China University of Science and Technology, Shanghai 200237, China 
WANG Zheng-dong East China University of Science and Technology, Shanghai 200237, China 
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中文摘要:
      目的 研究激光辅助氮化过程中,氮化层的开裂行为。 方法 利用 CO2 激光辅助氮化的方法在钛合金表面制备氮化钛涂层,观察氮化层的宏观、微观形貌,分析组织结构特征,测定氮化层残余应力,研究基体厚度、激光扫描工艺参数对氮化层表面形貌和裂纹情况的影响。 结果 钛合金经单道或多道激光氮化后,表面形成非均匀氮化钛层,其显微结构为沿主干轴交叉生长的枝状晶组织,存在数量和尺寸不等的显微裂纹。 较薄试样经单道激光氮化后,表面呈现较低的残余压应力状态,较厚试样则以拉应力为主;试样经多道激光氮化后,整个氮化区表面均呈现残余压应力状态。 结论 枝状氮化层与基体组织高度结合,不易脱落,但受基体约束作用,氮化层内的拉伸热应力导致其冷却过程中形成微裂纹。 随着试样厚度和氮化面积的增加,较高的热应力使得裂纹密度和裂纹尺寸增加,严重影响氮化层的质量。 残余应力是热应力和相变应力叠加的结果,对于多道激光氮化工艺而言,大面积氮化使得相变压应力增加,同时后热效应使得热应力降低,最终呈现出残余压应力状态。
英文摘要:
      Objective To study the cracking behavior of the nitride layer during the laser-assisted nitriding process. Methods CO2 laser was used to prepare titanium nitride coating on titanium alloy surface. The investigation was focused on the effects of sample thickness and process parameters on the surface topography and the cracking behavior . The macroscopic and microscopic morphology of the nitride layer was observed. A detailed analysis of crystalline structure and measurement of residual stress were performed. Results Inhomogeneous nitride layers with dendritic crystal along the main axis were successfully prepared by single or multiple laser scanning. Meanwhile, there were unequal size and number of cracks in the nitride layers. For the residual stress on the nitride surface exerted by single track of laser nitriding, thinner sample showed lower compressive stress state, and tensile stress took precedence in the thicker specimen conversely. However, the nitride surfaces by multiple laser nitriding showed residual compressive stress state. Conclusion The dendritic nitride layer was tightly bound to the matrix and did not easily fall apart .However, the formation of micro cracks in the cooling process was due to the internal heat stress, under the influence of the substrate constraints. Meanwhile, there was a progressive increase of crack density and dimension along with the increase of sample thickness and the area of nitride. It seriously affected the quality of the titanium nitride layer. The residual stress was the sum of the thermal stress and the phase transformation stress. When laser tracks were overlapped to produce a large area of nitride surface, there might be enough phase transformation to produce higher compressive stresses. In addition, the thermal stress level was reduced due to the effects of post-heat by successive overlapping tracks. Thus, the nitride surfaces by multiple laser nitriding showed residual compressive stress state.
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