高速铣削SiC_p/Al复合材料时聚晶金刚石刀具的磨损机理

Wear mechanisms of PCD tool in high-speed milling of SiC_p/Al composites

采用聚晶金刚石刀具(PCD),以600～1200m/min速度对SiCp/2009Al复合材料进行了高速铣削试验,研究了铣削时PCD刀具的磨损机理。使用扫描电镜(SEM)观察加工材料表面和刀具前/后刀面磨损带,X射线衍射仪分析已加工表面物相,并使用能谱(EDS)和激光拉曼谱对后刀面磨损带进行元素分析。结果表明,增强颗粒碳化硅的高频刻划和冲击是导致刀具晶粒脱落、磨粒磨损、崩刃、剥落的主要机制,切削高体积分数增强铝基复合材料、经热处理的复合材料或使用更高的切削速度时,PCD刀具会产生明显微裂纹。另外,增强颗粒体积分数是影响PCD刀具磨损的最显著因素,增强颗粒尺寸、工件材料热处理状态、刀具材料晶粒尺寸和冷却条件对刀具磨损均有显著影响。PCD刀具刀的寿命在70～240min之间。结论认为,增强颗粒机械冲击、切削振动和热冲击的综合作用是刀具产生微裂纹的主要原因。在高速铣削时的高温、高压下,工件材料中的铝元素和铜元素会向刀具有一定程度的扩散,PCD刀具在铜元素的催化作用下会发生轻微的石墨化磨损。

Milling tests for SiCp/2009Al composites were performed by using Polycrystal Diamond（PCD） tools at the cutting speed of 600-1 200 m/min and the mechanisms of tool wear were investigated.A Scanning Electron Microscope（SEM） was used to examine the machined surfaces and tool wear land,an X-ray diffractometer（XRD） was used to analyze the substances on the machined surface and the laser Raman spectra and Energy Density Spectrometry（EDS） were taken to analyze the elements on the tool wear land.The results show that the tool grain breaking-off,abrasive wear,chipping and the peeling caused by the high frequency impact and the scrapt of SiC particles are the prevalent wear patterns.When high volume fraction materials or heat treated materials are milled,or the milling is at a higher cutting speed,micro-cracks will form on the PCD tools.Furthermore,volume fractions,average sizes of SiC particles,tool grain sizes,cooling and heat treating conditions have significant influence on the tool wear.It concludes that the life of PCD tools is in the range of 70-240 min.The micro-cracks are produced on the tool flank under the combined effects of SiC particle impact,cutting vibration and heat impact.Moreover,the aluminum and copper can be diffused into the tool matrix under the very high cutting temperature and cutting forces and the trivial graphitization is taken place on the PCD tools due to the catalysis of copper in the aluminum matrix.