微米及纳米金刚石涂层扁钻的制备及其切削性能

Fabrication and Cutting Performance of Micro-and Nano-crystalline Diamond Coated Spade Drills

目的研究微米金刚石薄膜(Microcrystalline diamond film,MCD film)和纳米金刚石薄膜(Nanocrystalline diamond film,NCD film)的微观组织结构和表面质量,以及由两种薄膜涂覆制成的微米金刚石涂层扁钻(MCD coated spade drill)和纳米金刚石涂层扁钻(NCD coated spade drill)在切削碳纤维增强复合材料(Carbon fiber reinforced plastics,CFRP)时的切削性能。方法采用热丝化学气相沉积法在硬质合金扁钻上分别制备MCD薄膜和NCD薄膜。使用扫描电子显微镜观察金刚石薄膜的表面和横截面形貌,利用白光干涉表面轮廓仪测量薄膜的表面粗糙度值,使用拉曼光谱仪检测薄膜的结构成分,利用X射线衍射仪(XRD)检测薄膜的晶体结构和晶面取向,通过切削实验分析无涂层刀具和微、纳米涂层刀具的切削性能。结果制成的MCD和NCD薄膜涂覆均匀,两种薄膜的厚度都为8μm,晶面取向均以(111)面和(220)面为主。MCD薄膜晶粒棱角分明,平均晶粒尺寸为2~3μm,NCD薄膜的表面更光滑,平均晶粒尺寸为100 nm。MCD和NCD薄膜测定区域的表面粗糙度值分别为0.4μm和0.24μm。在相同的切削条件下,无涂层刀具钻削30个孔后,刀具已经达到了报废标准,不能继续使用。两种金刚石涂层刀具各钻削50个孔后,MCD和NCD涂层刀具后刀面的最大磨损量分别为0.192 mm和0.093 mm,均没有超过磨钝标准VB=0.2 mm(后刀面磨损带宽度),其中NCD涂层刀具的耐磨性最好。结论 MCD和NCD薄膜,尤其是NCD薄膜,能够有效地提高硬质合金刀具的耐磨性,延长刀具的使用寿命。

The work aims to study microstructure and surface quality of microcrystalline diamond film(MCD film)and NCD film(nanocrystalline diamond film),as well as cutting performance of MCD and NCD coated spade drills made from MCD and NCD films in cutting carbon fiber reinforced plastics(CFRP).The method of HFCVD was used to deposit MCD and NCD films on the surface of cemented carbide spade drills.Scanning electron microscope(SEM)was applied to observe surface and cross-sectional morphology of as-deposited diamond films,white-light interferometry was adopted to measure surface roughness of the films,Raman spectroscopy was used to assess structural components of the films,X-ray diffractometer(XRD)was used to characterize crystal structure and crystal orientation of the films,and cutting experiment was performed to investigate cutting performance of uncoated tool as well as as-deposited MCD and NCD coated tool.The two kinds of films were evenly coated with diamond grains on the tool,both films were 8μm thick,and crystal orientations were mainly in direction(111)and(220).The diamond grains of MCD film displayed pyramid structures with sharp edges and corners,the average grain size was about 2~3μm.MCD film contained angular grains,and average grain size was 2~3μm;and NCD film had a smoother surface,and average grain size was about 100 nm.Surface roughness value Ra of the MCD and NCD films in measured areas was 0.4μm and 0.24μm,respectively.Under the same cutting conditions,the uncoated tool reached rejection standardand could not be used any more after drilling 30 holes.After drilling 50 holes,MCD and NCD coated tools sustained the maximum abrasion loss of 0.192 mm and 0.093 mm,respectively on the flank,and none of them exceeded dullness standard VB=0.2 mm(width of flank wear land).The NCD coated tool exhibited the best wear resistance.The MCD and NCD films,especially NCD film,can effectively improve wear resistance of carbide cutting tools and extend service lives of the tools.