CrN and TiN Films Enhanced Surface Strength of Ti6Al4V Alloy

SI Biao, SHI Xiao-guang, SUN Lin-fan, DU Feng, ZHANG Kai-ce, ZHOU Yan-wen

Surface Technology ›› 2023, Vol. 52 ›› Issue (7) : 444-454.

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Surface Technology ›› 2023, Vol. 52 ›› Issue (7) : 444-454. DOI: 10.16490/j.cnki.issn.1001-3660.2023.07.041

CrN and TiN Films Enhanced Surface Strength of Ti6Al4V Alloy

  • SI Biao1, SUN Lin-fan1, DU Feng1, ZHOU Yan-wen1, SHI Xiao-guang2, ZHANG Kai-ce3
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Abstract

Hot wire enhanced plasma magnetron sputtering technique (PEMS) is based on the traditional magnetron sputtering assisting by tungsten wires as an electron source to enhance greatly the plasma density. The growing film is going to be bombarded by high-density ions, which significantly improve the film‘s density and adhesion. Chromium nitride (CrN) and titanium nitride (TiN) films were prepared on the surface of Ti6Al4V (TC4) alloy by this PEMS. The adaptabilities of the CrN and TiN films to TC4 matrix were studied. The TC4 matrix with a thickness of 3 mm and a length and width of 15 mm was polished, alcohol cleaned and dried before set into the vacuum chamber for plasma bombarded to further inside cleaning. The CrN and TiN films were deposited on the TC4 matrix only by varying the hot wire discharge current from 0 A to 16 A and 32 A, respectively. The surface and cross-sectional morphology were observed by SIGMA HD field emission electron microscope, and the element content was measured. An X‘ pert Powder X-ray diffractometer was used for phase analysis, with a scanning range of 20°-100°, scanning time of 8 min, and 0.03 (°)/step. The internal stress of the film was calculated by sin2ψ method, whose ψ deviation was based on the Grazing Incidence X-Ray Diffraction (GIXRD) test. Each film‘s thickness was measured by an Alpha-step D-100 profilometer. A G200 nano indentation tester was used to measure the nano hardness and elastic modulus of the matrix and films. A Rockwell hardness tester with a load of 1 470 N was used to test the adhesion by judging the failure edge of the indentation. The friction and wear properties of the films were evaluated by a MS-T3001 friction and wear tester. The results showed that the surface morphology of the films changed from loose pyramid to dense sphere and the columns got compact. The preferred orientations of the films changed from (111) with low strain energy to (200) with low surface energy, as the increase of hot wire discharge currents from 0 A to 32 A, i.e., the increases of the plasma density. Without assisting of the discharge current, the internal stress of the TiN film was higher than that of the CrN film. With the increase of the discharge currents, the increases of internal stresses of TiN films were much slow than those of the CrN films. As a result, the internal stresses of the TiN films became lower than those of the CrN films as the discharge currents increased. The nano-hardness and modulus of the CrN films were lower than those of TiN films, although they increased with the discharge currents. Indentation test showed that the films were well bonded to the matrix. The low load friction and wear test showed that the wear losses of TiN films with high hardness and modulus were the lowest. In conclusion, the increase of internal stress in TiN film with higher hardness and modulus is relatively low, and the TiN film with high modulus and hardness and low internal stress is more suitable for the modification of Ti6Al4V matrix under relatively low wear load of 2.94 N.

Key words

TC4 titanium alloy; plasma enhanced magnetron sputtering; plasma density; nitride film, low load friction

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SI Biao, SHI Xiao-guang, SUN Lin-fan, DU Feng, ZHANG Kai-ce, ZHOU Yan-wen. CrN and TiN Films Enhanced Surface Strength of Ti6Al4V Alloy[J]. Surface Technology. 2023, 52(7): 444-454
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