Ni基指数分布梯度熔覆层低应力多碰趋表效应

发布时间：2018-04-04 08:18

本文选题：指数梯度涂层　切入点：多次碰撞　出处：《表面技术》2017年06期

【摘要】：目的研究在低应力多碰条件下,在零件表面激光熔覆制备指数分布梯度涂层的效应。方法采用网格坐标划分法,在低应力条件下通过对Ni基指数分布梯度熔覆层的0Cr18Ni9试件进行多碰试验,获取变形数据,计算获得变形率,绘制规律曲线。借助工具显微镜,获得碰撞前后组织金相图。结果采用的碰撞应力仅有115 MPa,远低于涂层材料与基体的静压缩屈服强度,但指数分布的梯度涂层发生了可测的塑性变形,第一网格层变形率最为明显,达到了18.97%,第二网格层变形率为15.03%,靠近基体的最后一个网格层的变形率为0.29%,可以表明指数分布梯度涂层在低应力多碰后的形变具有"趋表效应"。基体的形变情况与梯度涂层的形变基本一致,从距表面6 mm处开始,涂层与基体结合处由于有瞬间激光高温熔覆,出现了应变的突变现象,宏观塑性变形增大,变形率突增到3.92%,但基体的形变总的来说也符合"趋表效应"。同时借助金相图看到的晶体滑移现象也证实了这一点。结论在低应力多碰作用后,试件表层的累积变形量最大,随着涂层深度的增加梯度减小,表明具有"趋表效应",同时抗多冲形变的能力显著增强。
[Abstract]:Aim to study the effect of laser cladding on the surface of parts under the condition of low stress and multiple impact.Methods the grid coordinate partition method was used to obtain the deformation data, calculate the deformation rate and draw the regular curve by multi-impact test on the 0Cr18Ni9 specimen of the Ni-based exponential distribution gradient cladding coating under low stress condition.With the aid of a tool microscope, metallographic diagrams of the structures before and after collision were obtained.The results show that the impact stress is only 115 MPA, which is far lower than the static compressive yield strength of the coating material and substrate. However, the gradient coating with exponential distribution has a measurable plastic deformation, and the deformation rate of the first grid layer is the most obvious.The deformation rate of the second grid layer is 15.03, and that of the last grid layer near the substrate is 0.29, which indicates that the deformation of the gradient coating with exponential distribution has a "tendency effect" after low stress and multiple collisions.The deformation of the substrate is basically consistent with that of the gradient coating. Starting from 6 mm away from the surface, because of the transient laser cladding at the interface between the coating and the substrate, there is a sudden phenomenon of strain, and the macroscopic plastic deformation increases.The deformation rate increases to 3.92, but the deformation of the matrix also accords with the "tendency effect".At the same time, the phenomenon of crystal slip can be seen by metallography.Conclusion after low stress and multiple impact, the accumulated deformation of the surface layer of the specimen is the largest, and the gradient decreases with the increase of coating depth, which indicates that there is a "tendency effect", and the ability of resisting multi-impact deformation is obviously enhanced.
【作者单位】：苏州工业职业技术学院;苏州大学激光制造技术研究所;
【基金】：国家自然科学基金(10972150) 江苏高校品牌专业建设工程资助项目(PPZY2015B186)~~
【分类号】：TG174.44;TN249

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