A solid-state cold-spray technique was employed for depositing the copper-coated graphite reinforced copper-based composite coatings on aluminum alloy 6061 T6 substrate under different process parameters. The optimum process parameters of the cold-sprayed coatings were predicted in terms of surface roughness, thickness and adhesion. The surface roughness was measured using a 3D profilometer, the thickness and element constitution were detected by an optical microscope and scanning electron microscope furnished with an energy-dispersive spectral analyzer and the adhesion was detected by the scratch test method. The microstructures of the deposited coatings were also observed by a scanning electron microscope. The results show that when the coating is not oxidized and dense, the copper-coated graphite reinforced copper-based composite coating at 800 °C, 5.5 MPa, possesses the lowest surface roughness, the maximum thickness and the highest adhesion among the cold-sprayed coatings. In addition, the surface roughness, thickness and adhesion of the deposited coatings are all linear with particle velocity.

Ultrasonic pulse frequency tungsten inert gas welding technology was adopted to join Ti-22Al-25Nb alloy. There were some cracks in the Ti-22Al-25Nb alloy weld joint after post-weld heat treatment. The hardness and Young’s modulus of α₂, O, and β/B2 phases in Ti-22Al-25Nb alloy were examined with an in situ nanoindentation technique. The phase transition stresses of three different phases in the weld joint of Ti-22Al-25Nb alloy were analyzed to explain why cracks occur in the weld joint of Ti-22Al-25Nb alloy during post-weld heat treatment. The results show that mean hardness is highest for the α₂ phase, second-highest for the O phase, and lowest for the β/B2 phase; the mean Young’s modulus has the same trend in Ti-22Al-25Nb alloy. Phase transition stress results in cracks in the weld joint of Ti-22Al-25Nb alloy during post-weld heat treatment. By improving post-weld heat treatment, the ultimate strength of the Ti-22Al-25Nb alloy weld joints reaches 750 MPa, which is 72.5% that of the base material.

Copper-coated graphite and copper mixture powders were deposited on AZ31B magnesium alloy and 6061 T6 aluminum alloy substrates under different process parameters by a solid-state cold spray technique. The microstructure of the copper-coated graphite and copper composite coatings was visually examined using photographs taken with an optical microscope and a scanning electron microscope. The surface roughness of the coatings was investigated with a 3D profilometer. The thickness of the coatings was determined through the analysis of the microstructure images, while the adhesion of the coatings was characterized using the scratch test method. The results indicate that the surface roughness of the coatings sprayed on the two different substrates gradually decreases as gas temperature and gas pressure increase. Additionally, the thickness and adhesion of the coatings deposited on the two different substrates both increase with an increase in gas temperature and gas pressure. Comparing the surface roughness, thickness, and adhesion of the coatings deposited on the two different substrates, the surface roughness and adhesion of the coatings on the soft substrate are greater than those of the coatings on the hard substrate, while the thickness of the coatings is not obviously affected by the hardness of the substrate. Furthermore, it is noteworthy that the surface roughness, thickness, and adhesion of the copper-coated graphite and copper composite coatings sprayed on the two different substrates exhibit a distinct linear relationship with particle velocity.

The development process of electrospark deposition (ESD) technology is reviewed, and the principles and differences of ESD technology are discussed in this review. Based on the research status regarding the ESD of titanium alloys, the promotion effect of ESD technology on wear resistance, corrosion resistance, oxidation resistance at high temperatures, and the biocompatibility of titanium alloys was elaborated on. For example, with the use of ESD technology to prepare Ti–Al, TiN, Ni–Cr, and other hardening coatings with high hardness, the maximum hardness of the deposited layer is six times higher than that of the substrate material, which greatly reduces the loss of the material surface in the process of friction in service, and has a high wear–resistance effect. The preparation of a single–phase lamellar coating is more beneficial for improving the oxidation resistance of the substrate. Carbide and a nano–porous coating can effectively enhance the bone integration ability of implants and promote biocompatibility. The application of ESD technology in the surface modification of titanium alloys is reviewed in detail. Finally, the development direction of ESD technology for titanium alloys is proposed.