TC4钛合金表面涂层改性:CrN素多层

Surface Modification of TC4 Titanium Alloy by CrN Prime Multilayer

目的提高TC4钛合金的硬度和耐磨损性,改善CrN硬质涂层与TC4钛合金的适应性。方法采用等离子体增强磁控溅射系统,通过调节热丝放电电流,在TC4钛合金基体表面沉积疏密CrN单层和素多层涂层。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、纳米压痕仪、洛氏压痕仪、摩擦磨损仪以及台阶仪,表征涂层形貌、成分、物相及性能。采用动电位极化法表征涂层的耐腐蚀性。结果当热丝放电电流为较低的4 A×4时,沉积的CrN单层涂层为具有针孔、孔洞等缺陷的疏松结构,8 A×4沉积的CrN单层涂层具有致密结构,周期性调节热丝放电电流则获得疏密交替的CrN素多层涂层。CrN涂层均由单一面心立方结构的CrN相组成,疏松CrN单层涂层的衍射晶面为(111)、(200)、(220)及(222),致密CrN单层涂层沿(111)晶面择优生长,随着疏密子层调制比的增大,CrN素多层涂层的(111)衍射峰不断增强。疏松CrN单层涂层的最小H和最大E分别为13.0 GPa和207.5 GPa,调制比为1:4的疏密CrN素多层涂层的最小H和最大E分别为17.0 GPa和257.4 GP。在1470 N载荷下洛式压痕法表明,致密CrN单层涂层的结合强度最低,等级为HF5,其余涂层均为HF1—HF4。CrN涂层的自腐蚀电位较TC4钛合金均发生了正移。结论CrN硬质涂层可以有效提高TC4钛合金的硬度和耐磨损性,表面得到明显强化。周期性调节等离子体密度所沉积的疏密CrN素多层涂层与单层相比,涂层性能明显改善。

This propose is to improve the hardness and wear resistance of TC4 titanium alloy and to improve the adaptability of CrN hard coating to TC4 titanium alloy.By using plasma-enhanced magnetron sputtering system,loose and dense CrN monolayer and multilayer coatings are deposited on surface of TC4 titanium alloy substrate by adjusting the hot wire discharge current.The morphology,composition,phase structure and performance of CrN coatings are characterized by X-ray diffraction(XRD),energy dispersive spectroscopy(EDS),scanning electron microscopy(SEM),nano-indentation,Rockwell indenter,ballon-disk tribometer and step tester.The corrosion resistance of CrN coatings is characterized by the electrokinetic polarization method.When the hot wire discharge current is 4 A×4,the morphology of the CrN monolayer coating are loose structure with the defects of pinholes;that of CrN monolayer coating deposited at the discharge current of 8 A×4 is dense and defect free structure.The CrN prime multilayer coating with alternating loose and dense sublayers are obtained by periodically adjusting discharge currents.The CrN coatings are composed of a single CrN phase with a face-centered cubic structure.The diffraction orientations of the loose CrN monolayer coating are(111),(200),(220)and(222).On the other hand,the dense CrN monolayer coating showed its preferred orientation of(111)plane.The(111)diffraction peak of the CrN prime multilayer coatings increased with the increases of the modulation ratio of the loose sublayer to dense one.The H and E of the loose CrN monolayer coating and the CrN prime multilayer coatings with a modulation ratio of 1:4 are the minimum and maximum,namely 13.0 GPa and 207.5 GPa,17.0 GPa and 257.4 GPa,respectively.The Rockwell indentation method under a load of 1470 N shows that the dense CrN monolayer coating is with the weakest bonding strength,the grade of HF5,the remaining coatings are within the grades of HF1-HF4.The self-corrosion potential of CrN coatings is positively shifted compared to that of TC4 titanium alloy.CrN hard coating can effectively improve hardness and wear resistance of TC4 titanium alloy.Compared with a monolayer,CrN prime multilayer coatings deposited under periodic adjustment of the plasma density exhibited significantly improved performance.