Abstract
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, ball- on-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.
Key words
TC4 titanium alloy; prime multilayer coating; hardness; wear resistance; corrosion resistance
Cite this article
Download Citations
LI Jin-long, ZHOU Yan-wen, ZHANG Kai-ce, HUANG Zhen, QI Ji-long, WANG Ya-nan, GUO Yuan-yuan.
Surface Modification of TC4 Titanium Alloy by CrN Prime Multilayer[J]. Surface Technology. 2021, 50(4): 215-224
{{custom_sec.title}}
{{custom_sec.title}}
{{custom_sec.content}}