单晶硅纳米切削中C—C键断裂对金刚石刀具磨损的影响

本文基于分子动力学方法模拟金刚石刀具纳米切削单晶硅,从刀具的弹塑性变形、C—C键断裂对碳原子结构的影响以及金刚石刀具的石墨化磨损等方面对金刚石刀具的磨损进行分析,采用配位数法和6元环法表征刀具上的磨损碳原子.模拟结果表明:在纳米切削过程中,金刚石刀具表层C—C键的断裂使其两端碳原子由sp3杂化转变为sp2杂化,同时,表面上的杂化结构发生变化的碳原子与其第一近邻的sp2杂化碳原子所构成的区域发生平整,由金刚石的立体网状结构转变为石墨的平面结构,导致金刚石刀具发生磨损;刀具表面低配位数碳原子的重构使其近邻区域产生扭曲变形,C—C键键能随之减弱,在高温和高剪切应力的作用下,极易发生断裂;在切削刃的棱边上,由于表面碳原子的配位严重不足,断开较少的C—C键就可以使表面6元环中碳原子的配位数都小于4,导致金刚石刀具发生石墨化磨损.

超精密切削镍磷合金镀层模辊及刀具磨损特性研究

研究了金刚石刀具对具有镍磷合金(NiP)合金镀层的压印模辊进行长距离连续切削时刀具的磨损情况。首先,通过金刚石超精密辊筒车床对大尺寸NiP合金镀层模辊进行精密V槽切削。然后,利用加工好的V槽模辊进行卷对卷压印实验,通过压印片材上不同位置的表面粗糙度测量分析了刀具从切削开始到结束过程中的磨损情况。最后,利用Advant Edge软件进行了有限元模拟切削过程中刀尖温度分布状态,同时对比了切削过程中不同位置处刀尖的轮廓线。实验结果表明:金刚石刀具切削NiP合金镀层模辊时刀具的磨损过程是有一个先慢后快的规律,即刀尖切削刃发生石墨化转变产生为崩刃以后,刀具的磨损速率明显加快。

SCD及PCD刀具超精密车削SiC_p/2024Al复合材料适应性对比研究

选择天然单晶金刚石(SCD)和聚晶金刚石(PCD)刀具,对SiCp/Al复合材料超精密车削时的刀具磨损、加工表面质量和切屑形态进行了对比试验研究。结果表明:刀具交替切削硬脆SiC颗粒和塑性铝合金基体而承受的交变应力,以及SiC增强颗粒对切削刃高频率的冲击作用是促使SCD刀具发生崩刃和剥落的主要原因,而增强颗粒的磨粒磨损与铝合金基体中铜元素催化作用的共同作用则是SCD刀具后刀面发生严重化学磨损的内在机制。积屑瘤不断生长和脱落致使PCD刀具产生粘结磨损。虽然PCD和SCD刀具可获得相同或相近的Ra,但前者获得的加工表面含有更多的微坑洞和划痕等缺陷;同时,PCD刀具获得的切屑与SCD刀具的相比更为细碎。在试验所用切削条件下,当切削路程小于7 km时,PCD刀具具有较稳定的切削性能。

Wear of CVD thick film diamond cutter while machining laminated flooring

The wide application of high pressure laminated (HPL) flooring has an insistent need for cutting tools with an excellent performance and fine cutting quality. Chemical vapor deposition (CVD) thick film diamond is a promising material for the machining of HPL flooring. In the present work, CVD thick film diamond tools were used to mill the wear resistance layer of HPL flooring. Wear volumes of flank face were examined by optical microscopy, and micro wear morphologies were observed by scanning electron microscopy (SEM). The experiments revealed that the predominant wear characteristics of CVD diamond tools were transgranular cleavage wear and intergranular peeling of the CVD diamond. Experimental results also showed that twin characteristic, cavity defect, micro crack and grain size of CVD thick film diamond contributed greatly to the wear process of CVD thick film diamond tools. The effects caused by the factors were also analyzed in detail in the paper.