Preparing Of Ti-DLC Gradient Functional Films On 17-4PH Steel Surface And Research On Its Microstructure And Properties

Diamond-like carbon（DLC）has excellent mechanical properties（high hardness and elastic modulus,low coefficient of friction）,electromagnetism,optical properties（translucent）,biocompatibility and chemical stability and has become an important new functional films.However,the study found that DLC films mainly has two problems of large internal stress and poor thermal stability.So this paper will use the closed-field non-equilibrium magnetron sputtering ion plating（UBMS）technology to prepare different content of Ti doped gradient functional DLC films in order to solve these two problems and explore the effect of content of Ti on microstructure and properties of DLC films.The results show that the prepared Ti-DLC films is smooth,flat,dense and the particles are uniform and small,the Rq is in the range of 8.45nm²1.6nm.And with the titanium target current increasing from 0.4A to 0.8A,The surface roughness increases.GXRD analysis shows that the prepared Ti-DLC films show a broadened carbon diffraction peak at near 44.5°,and both TiO and TiO₂ nanocrystals are formed.In addition,titanium target current is 0.4A sample also formed TiN_0.3 nanocrystal.X-ray analysis shows that Ti-DLC films surface elements are mainly in the form of Ti-O and Ti-N bonding,corresponding to the compounds are TiO,TiO₂ and TiN_0.3 respectively.In addition,the C1 s XPS peak can be divided into sp³ C peak,sp² C peak and C-O peak,and the content of sp³ C of different titanium target current Ti-DLC films is 49.03% 53.31%.It is found that the higher titanium target current is favorable for sp³ C bonding,and the titanium content increases from 0.82 at.% to 1.97 at.% with the titanium target current increases from 0.3A to 1.0A.The higher titanium target current causes the sp³ C to shift to the upper and reduce its FWHM.Raman spectroscopy showed that D peak position offset is very small and G peak position offset is more serious and ID/IG（RI）is in the range of 1.1 to 1.7.The results show that the Ti-DLC films with the target current of 0.4A has the maximum hardness（50.697GPa）and the elastic modulus（368.185GPa）.Titanium content in range of 0.8¹.1%,with the titanium content increases,the nanohardness and elastic modulus increases,then there is the opposite trend.The wear and tear properties of the untreated matrix are mainly caused by severe oxidation wear and adhesive wear.The wear width and depth are about 700μm and 100μm respectively.The coating specimen only has a slight abrasive wear,The wear width and depth are about 80μm and 0.1μm respectively.Compared with untreated matrix,the maximum friction coefficient decreased by 96.15%,the maximum wear rate is 99.10%.In general,the best resistance to friction and wear properties of titanium target current of 0.3A Ti-DLC film.Compared to the untreated matrix,the coated sample has a wider passivation zone.The sample（ITi=0.3A）has the lowest self-etching current,the sample（ITi=0.4A）has the highest pitting potential and the widest passivation zone,the sample（ITi=0.6A）has the highest self-corrosion potential.In summary,the best process is the titanium target current 0.3A to 0.5A.