高速干铣削钛合金时涂层硬质合金刀具磨损机理研究

Wear Mechanisms of Coated Carbide Tools in High-Speed Dry Milling of Titanium Alloy

采用CVD涂层硬质合金可转位立铣刀对钛合金(Ti-6Al-4V)进行了高速干铣削试验,采用扫描电子显微镜(SEM)观察刀具的磨损形貌,通过能谱分析(EDS)分析失效刀具表面的元素分布,并对刀具的主要磨损机理进行了分析.研究结果表明:使用涂层硬质合金刀具高速干铣削Ti-6Al-4V时,刀具的失效机理主要为磨粒磨损、粘结磨损、氧化磨损、扩散磨损和热-机械疲劳磨损的综合作用.刀具刚参与切削时,刀具后刀面会产生粘结和由于摩擦引起的擦伤,粘结层在断续冲击作用下的脱落过程还会造成后刀面涂层的剥落;随着刀具进一步的磨损,涂层剥落、粘结磨损及磨粒磨损伴随整个刀具失效过程,且还会出现氧化磨损、扩散磨损和疲劳裂纹等.切削速度越高,新产生的钛合金切屑就越容易燃烧,使刀具粘结、氧化和扩散以及热-机械疲劳等磨损加剧.

A series of experiments was conducted in high speed dry milling of Ti-6Al-4V alloy with CVD coated carbide indexable cutters.The main tool wear mechanisms were discussed by observing tool wear morphology utilizing scanning electron microscopy and detecting the element distribution of the worn tool surface using energy dipersive spectroscopy.The experimental results indicate that the tool failure mechanisms were synergistic interaction among abrasive wear,adhesive wear,oxidation wear,diffusion wear and thermal-mechanical fatigue wear.Just after the cutting tool was engaged into the workpiece,adhesion and scratches caused by friction were observed on tool flank face,and the adhesive layer was subjected to cyclic impacts in the intermittent cutting process which would lead to delamination of coating.During the process of tool degradation,coating delamination,adhesive wear and abrasive wear appeared in the process of tool failure.In addition,oxidation wear,diffusion wear and fatigue cracks were observed.With the increasing cutting speed,the newly produced chips can burn more easily and the degree of adhesion,oxidation and diffusion and thermal-mechanical fatigue wear increased.