硬质合金激光改性协同仿生微织构对硼掺杂金刚石涂层性能的影响

Effects of Laser Surface Modification of Cemented Carbide and Bionic Microtexture on Properties of Boron-doped Diamond Coatings

目的研制应用于超精密加工领域的高性能金刚石涂层,探究硬质合金基体表面激光微织构对硼掺杂金刚石(BDD)涂层沉积质量的影响,分析不同类型的仿生微织构对基–膜结合强度、工具切削性能的改善效果及原因。方法在硬质合金表面使用激光脉冲制备不同类型的仿生微织构,并通过热丝化学气相沉积(HFCVD)法在刀具表面沉积BDD涂层。采用数显洛氏硬度计(HRS-150)、超景深三维显微镜、扫描电子显微镜(SEM)、能谱仪(EDS)、白光干涉表面轮廓仪、拉曼光谱(Raman)对样品进行表征。通过压痕试验及铣削试验研究涂层的附着强度和刀具的切削性能。结果激光微织构边缘发生表面硬化。激光微织构区域沉积BDD涂层后,基体表面缺陷显著降低,织构内部金刚石晶粒更密集,沉积质量提升,三角织构(TT)边缘的金刚石颗粒堆积坡度最缓,不同类型的织构化BDD涂层的粗糙度、金刚石纯度、切削性能及附着强度均不同,涂层附着力与表面硬度呈正相关。硼掺杂三角织构(BDTTD)涂层刀具具有最佳的切削性能。结论织构边缘和内部具有更高的金刚石二次成核率和沉积质量。织构的存在可以提升BDD涂层的附着强度和刀具性能,并且织构边缘的涂层附着力最强,这些得益于激光烧蚀及仿生微织构对硬质合金表面的硬化及对BDD涂层内在缺陷的修复。

The mismatch between the coefficients of thermal expansion of diamond and WC-Co cemented carbide causes hot filament chemical vapor deposition(HFCVD)diamond coating tools to be prone to coating flaking and wear,which severely limits their promotion in the field of ultra-precision machining.In this work,in order to prepare high performance diamond coating applied in the field of ultra-precision machining,different types of bionic microtexture were fabricated on the surface of carbide tools by laser technology,and boron-doped diamond(BDD)coatings were deposited on the surface of tools by HFCVD method.The effect of laser microtexture on the deposition quality of BDD coatings on hard alloy substrates was investigated,and the improvement effect and reasons of different types of bionic microtexture on substrate-coating bonding strength and cutting performance of tools were analyzed.The surface hardness of samples was studied by digital rockwell hardness tester(HRS-150).The surface morphology and elemental composition of the samples were observed by super depth 3D microscope(VHX-5000),scanning electron microscope(SEM)and energy dispersive spectrometer(EDS).The roughness of coatings was measured by white light interferometer.The composition of coatings was analyzed by Raman spectroscopy.The effects of different microtextures on coating adhesion strength and cutting performance were studied by indentation and milling tests.Surface hardening occurred at the edge of microtexture,and the hardening effect decreased sharply when the distance from the edge exceeded 75μm.After laser treatment,the content of Co element increased from 3.3%to 4.6%,while after combination with acid-base two-step method,the content of Co element decreased from 0.7%to 0.5%.After laser zone deposition of BDD coating,surface defects were significantly reduced and diamond grains were denser in texture.After the deposition of BDD coatings in the laser microtexture regions,the surface defects of the substrate were significantly reduced,and the diamond grains in the texture were denser,and the deposition quality was improved.In particular,the slope of diamond particles at the edge of triangle texture(TT)was the slowest.Different types of textured BDD coatings had different roughness,diamond purity,cutting performance and adhesion strength and coating adhesion was positively correlated with surface hardness.The performance of untextured BDD coated tools was better than that of untextured groove textured(GT)tools,and that of textured BDD coated tools are better than those of the former two,among which the boron-doped triangular textured(BDTTD)coated tools had the best cutting performance.The following conclusions can be drawn from the above phenomena:the acid-base two-step method combined with laser technology creates a good substrate environment for HFCVD diamond growth.The texture can improve the deposition quality of BDD coatings,and the edge and interior of the texture have higher secondary nucleation rate of diamond.The existence of texture can improve the adhesion strength and tool performance of BDD coatings and the coating adhesion at the texture edge is the strongest,which benefits from the hardening of cemented carbide surface and the repair of the inherent defects of BDD coatings by laser bionic micro-texture.