Tribocorrosion and Surface Protection Technology of Titanium Alloys: A Review

Abstract

Titanium alloy has the advantages of high specific strength, good corrosion resistance, and biocompatibility and is widely used in marine equipment, biomedicine, aerospace, and other fields. However, the application of titanium alloy in special working conditions shows some shortcomings, such as low hardness and poor wear resistance, which seriously affect the long life and safe and reliable service of the structural parts. Tribocorrosion has been one of the research hotspots in the field of tribology in recent years, and it is one of the essential factors affecting the application of passivated metal in corrosive environments. In this work, the characteristics of the marine and human environments and their critical tribological problems are analyzed, and the research connotation of tribocorrosion of titanium alloy is expounded. The research status of surface protection technology for titanium alloy in marine and biological environments is reviewed, and the development direction and trends in surface engineering of titanium alloy are prospected.

Keywords: marine; plasma surface engineering; titanium alloys; tribocorrosion.

Figure 1

Titanium alloy application scenarios and surface modification techniques and principles for improving the tribocorrosion properties of titanium alloys [55,56,57,58].

Figure 2

Factors influencing tribocorrosion. Adapted from Ref. [86].

Figure 3

Schematic of the proposed process of tribocorrosion (measured by the volume of material removed) with a single asperity, composed of a combination of tribocorrosion mechanisms (plastic deformation, oxide passivation, and ion dissolution) [87].

Figure 4

(a) Schematic electrochemical setup (a standard 3-electrode cell) used during basic corrosion test. (b) Schematic tribocorrosion setup. (c) Standard protocol used during tribocorrosion test (OCP—open circuit potential; PS—potentiostatic test; EIS—electrochemical impedance spectroscopy) [88].

Figure 5

Wear-accelerated corrosion mechanism: (a) 10 mN; (b) 100 mN; (c) 1 N [45].

Figure 6

STEM images of an FIB section of the worn surface of the Ti64ELI. (a) Bright-field image, (b) crystal orientation image using precession electron diffraction [95].

Figure 7

(a) Total hip replacement implants [135]; (b) lateral male taper and medial half-sleeve female tapers after 22 months implantation, (c) proximal female and male tapers after 27 months implantation [136], (d) female taper adapter, and (e) male stem taper after 43 months implantation [137].

Figure 8

(a) Three-body abrasions at the surface of the implant material [140], (b) degradation of a titanium implant due to microplowing and active metal dissolution phenomena [141].

Figure 9

(a,b) Cross-section metallography of nitriding sample, (c) cross-section SEM-EDS of nitriding sample, (d) OCP curves of nitriding and untreated sample, (e) polarization curve before and after tribocorrosion, (f) current and COF of nitrided and untreated sample [194].

Figure 10

Tribocorrosion characterization of different samples: (a) potentiodynamic polarization curves, (b) evolution of OCP and COF with sliding time for Ti6Al4V (black), Ti6Al4V/SrTiO₃ (red), Ti6Al4V/TiO₂ (green) and Ti6Al4V/TiO₂/SrTiO₃ (blue), (c) material loss volume, and (d) 3D surface morphologies. (e) Schematic diagram of the TiO₂/SrTiO₃ coating with photocatalytic, antibacterial, osteogenesis, and tribocorrosion resistance properties [201].

Figure 11

(a) Schematic illustration underlying the incorporation mechanism of Cu_xO phases into the TiO₂ layer, (b) OCP and COF before, during, and after sliding in SBF condition (WE: working electrode, CE: counter electrode, RE: reference electrode), (c) the mass loss, (d) the 3D topographies [218].

Figure 12

Surface and cross-sectional SEM images of CrMoSiN (a,b), TEM (c), and HRTEM (d) images of CrMoSiN coating, (e) OCP measurements and respective friction coefficient curves of CrSiN and CrMoSiN coatings, Schematic illustration of tribocorrosion mechanism for Cr(Mo)SiN coatings in artificial seawater (f–h) [241].

Figure 13

(a–c) SEM images of worn scars on the surfaces of different samples, (d–f) magnification SE/SEM images of the worn sub-surfaces of different samples, (g–i) schematic tribocorrosion mechanisms of different samples [155].

Figure 14

(a,b) SEM images of wear track sliding, (c) wear mechanism models of different coatings in simulated body fluid, (d) friction coefficient curves of various coatings, (e) potentiodynamic polarization curves of various coatings, (f) evolution of OCP values of different coatings [247].

Figure 15

(a) The schematic of the laser cladding processes, (b) COF, and (c) OCP curves of TC4. Mechanism diagram of tribocorrosion process under the different conditions: (d) 2 BN, (e) 4 BN, and 6 BN coatings [163].

Figure 16

A schematic diagram for wear mechanism of the as-prepared coatings: (a1–a3) MAO-based coating, (b1–b3) duplex TiN-MAO coating [283].

Figure 17

(a,b) Surface and cross-section SEM images by secondary electrons for the DLC coatings obtained with PEMS + PIID techniques, (c) OCP measurements before, during, and after tribocorrosion reciprocal sliding test in 1 × PBS solution for the PIID DLC coating, PEMS + PIID DLC coating, and Ti-6Al-4V uncoated samples, (d) SEM images of tribocorrosion wear tracks with measured width at left and center track enlarged at right for the (i) PIID DLC coating, (ii) PEMS + PIID DLC coating and (iii) Ti-6Al-4V uncoated samples [284].

Figure 18

Models of crystal structure, lattice distributions, and adhesive force for the Cr-DLC coating−CrN interlayer−nitrided TA system: (a) Model of crystal structure, (b) Lattice distribution of original TA, (c) Lattice distribution of the nitrided TA [286].