直流电化学两步处理精磨硬质合金表面对CVD金刚石涂层的影响

Effects of Two-step DC Electrochemical Pretreatment Method on Diamond Coatings on Fine Grinding Cemented Carbide Surfaces

经开刃、精磨处理而具实际加工能力的钨钴硬质合金刀具在制备CVD金刚石涂层前需进行基体前处理,但常规的化学预处理技术对其规模化应用时,会受到腐蚀效率,工艺重复性的限制。以精磨YG6硬质合金铣刀片为研究对象,采用直流弧光放电等离子体CVD设备、SEM、激光Raman光谱仪、原子吸收光谱仪、表面轮廓仪、洛氏硬度计等,研究了直流电化学两步处理(先直流电化学腐蚀,后酸浸蚀)对精磨硬质合金基体以及对金刚石涂层的影响。结果表明:直流电化学两步处理能有效去除精磨硬质合金基体表面的WC"表皮",并降低基体表面Co含量;通过改变直流电化学腐蚀时间,可平衡基体表面粗糙度、基体表面Co浓度去除以及去Co后基体表面硬度的关系,可有效调控CVD金刚石涂层从微米向纳米晶型的转变过程,并具有较好的可控性;结合基体/涂层硬度、薄膜品质及膜基附着力等指标,优化了直流电化学两步处理工艺参数为:第一步,在10%NaOH电解液中经直流1A电化学腐蚀5min;第二步,王水再腐蚀90s。

Due to the fine grinding WC-Co substrate which has been polished to provide a keen/cutting edge must be pretreated before depositing CVD diamond coating.However,conventional chemical etching methods may have the drawbacks of difficulties in corrosion efficiency and process repeatability for its large-scale applications.An investigation had been carried out to study the influence of the two-step DC electrochemical pretreatment（firstly using DC electrolytic etching,and then using acid etching） on the fine grinding cemented carbide substrates and diamond coatings by means of Scanning Electron Microscope（SEM）,profilometer,Atom Absorption Spectrometry（AAS）,Energy dispersive X-ray diffraction analysis（EDXA） and Rockwell hardness tester respectively.The results showed that the two-step DC electrochemical pretreatment method can effectively remove the ＂skin＂ of grinding substrates surface and reduce the Co content.Through changing the electrolytic time,the relationship amongst substrate surface roughness,the substrate surface Co concentration removal and the hardness of substrate surface after Co removed are balanced,and effectively control CVD diamond coating from microcrystalline cubic-octahedron to cauliflower type nanocluster transformation process,which has a good controllability.According to the substrate/coating hardness,coating quality and coating adhesion strength testing results,optimized the best process parameters of the two-step DC electrochemical pretreatment method at fine grinding cemented carbide substrates,which firstly using DC（direct current） 1A electrolytic etching for 5 minutes in 10% sodium hydroxide（NaOH） solution,and then etched in an aqua regia（HNO3∶3HCl∶H2O=1∶1∶1） solution for 90 seconds.