微裂纹缺陷对CVD金刚石涂层微刀具损伤失效的影响研究  

Effect of Micro-crack Defects on Damage and Failure of CVD Diamond Coating Micro-tools

作　　者：白清顺[1] 张亚博 王永旭 何欣[1] BAI Qing-shun;ZHANG Ya-bo;WANG Yong-xu;HE Xin(Harbin Institute of Technology,Harbin 150001,China;Faw-Volkswagen Automotive Co.,Ltd,Beijing 100083,China)

机构地区：[1]哈尔滨工业大学,哈尔滨150001 [2]一汽-大众汽车有限公司,北京100083

出　　处：《表面技术》2021年第2期355-362,共8页Surface Technology

基　　金：国家自然科学基金(51575138,51535003)。

摘　　要：目的研究微裂纹缺陷在CVD金刚石涂层中的扩展规律,揭示CVD金刚石涂层微刀具的涂层脱落机理。方法基于ABAQUS开展预置涂层内部竖直微裂纹和涂层基底界面水平微裂纹的CVD金刚石涂层单向拉伸有限元仿真,分析单裂纹和多裂纹扩展过程中裂纹尖端的应力分布和应力强度因子变化规律。开展CVD金刚石涂层刀具微铣削Ti6Al4V实验,分析刀具的磨损形态和刀尖的断面形貌,验证仿真结果。结果涂层内部竖直微裂纹扩展到涂层基底界面时,裂纹尖端的应力强度因子小于硬质合金的断裂韧性537.6 MPa·mm1/2,大于金刚石的断裂韧性289.7 MPa·mm1/2,裂纹在界面发生偏转。涂层和基底界面间的水平微裂纹在扩展过程中裂纹尖端的应力强度因子小于金刚石和硬质合金的断裂韧性,裂纹沿着界面逐步扩展。CVD金刚石涂层刀具微铣削Ti6Al4V后表现出涂层脱落、刀尖破损和崩刃的损伤特征,其断面表现出穿晶断裂、沿晶断裂和微裂纹的形貌特征。结论涂层脱落损伤主要源于涂层内部竖直裂纹扩展诱导的涂层断裂和界面裂纹扩展引起的粘接层脱落。涂层内部竖直裂纹的竞争作用会抑制涂层断裂,粘接层水平裂纹间的耦合作用会加速涂层脱粘。To investigate the propagation law of micro-crack in CVD diamond coating and reveal the coating delamination mechanism of CVD diamond coating micro-tools.This paper establishes the uniaxial tension models of CVD diamond coating,which contained vertical micro-cracks in the coating and horizontal micro-cracks between the coating and the substrate in ABAQUS to analyze the stress distribution and stress intensity factor of crack tips in the single-crack propagation and multi-crack propagation,and conducts the micro-milling experiments of Ti6Al4V to analyze the wear and cross-sectional morphologies of the CVD diamond coating tool and verify the simulation results.When vertical micro-cracks of coating spread into the interface between the coating and the substrate,stress intensity factor of crack tips is lower than the cemented carbide fracture toughness of 537.6 MPa·mm1/2 and higher than the diamond fracture toughness of 289.7 MPa·mm1/2,and cracks deflect at the interface.When stress intensity factors of crack tips were less than the diamond fracture toughness and cemented carbide fracture toughness in the propagation of the horizontal micro-crack between the coating and the substrate,cracks gradually grow along the interface.After micro-milling experiments of Ti6Al4V,CVD diamond coating micro-tools showed coating delamination,tool-tip breakage,and chipping.The cross-sections of CVD diamond coating micro-tools showed transgranular fracture,intergranular fracture,and micro-cracks.The coating delamination mainly originates from the coating fracture induced by vertical micro-cracks in the coating and the horizontal micro-cracks in the interface between the coating and the substrate.The coating fracture can be inhibited by the competition effect of different vertical micro-cracks in the coating.And the coupling effect between the different horizontal cracks will accelerate the adhesive layer peeling.

关 键 词：CVD金刚石 微铣削 断裂 脱粘 涂层脱落 损伤失效 

分 类 号：TG174.4[金属学及工艺—金属表面处理] TG714[金属学及工艺—金属学]