Research Progress in Surface Enhancement Technologies for Titanium and Titanium Alloy Materials

Research Progress in Surface Enhancement Technologies for Titanium and Titanium Alloy Materials

Surface Nanofabrication

       As a new surface treatment technology, nanofabrication can achieve deep refinement of the surface grains of titanium and titanium alloys, down to the nanometer level, by using physical and chemical means without changing their material composition, fundamentally solving the problem of material surface fatigue resistance, and thus improving the surface corrosion resistance of titanium and titanium alloys, as well as enhancing their wear resistance in practical applications. By using methods such as shot blasting and supersonic particle bombardment, the processing tool is brought into full contact with the surface of the workpiece, causing the surface grains of titanium and its alloys to be broken by mechanical means, and then strengthened. By using high-energy shot peening surface nanofabrication technology on TC4, the grain size can be kept near 20nm, and the fatigue resistance of the material can be improved by the hardened layer on the surface with higher hardness than the original material. By treating TA2, a nanoscale surface layer with a grain size close to 30nm can be formed to improve the hardening degree of the material's deformation twinning. Moreover, under the condition of 623K, China is superior to the relevant specifications of the United States in the treatment of titanium and titanium alloys, and it is currently at the leading level. By using supersonic particle bombardment, Ti-6Al-4V alloy can be treated to derive a nanoscale equiaxed structure on its surface, with a grain size of about 20nm, which can increase the hardness of the alloy surface by more than double compared to the original material. However, this surface nanofabrication treatment was launched later, and has not been widely promoted.

Surface Permeation and Ion Implantation

      Different from surface nanotechnology, surface permeation and ion implantation involve doping metal or non-metal materials into titanium alloy matrix material, altering its surface composition, and producing a modified layer to enhance the surface resistance of the titanium alloy matrix. For example, non-metal materials such as nitrogen and carbon can be penetrated into the surface of titanium and titanium alloys or diffused with metal materials such as aluminum and molybdenum, thereby improving the wear and corrosion resistance of the titanium alloy matrix. Using mesh cathode glow discharge method, Ta can be plated on the surface of TC4 matrix, which can effectively improve the corrosion resistance performance of TC4 matrix. By using a solid powder embedding method and preparing a molybdenum permeation layer, the surface phase structure of TC6 can be significantly changed, and the surface hardness of TC6 can be increased to 1400HV. With the rapid development of science and technology and the deepening of vacuum technology research and use, ion implantation technology can be derived based on existing surface permeation technology. For example, using ion permeation of nitrogen, the hardness of TA7 titanium alloy surface can be increased to 1200HV. By using the arc glow ion non-hydrogen permeation carbon technology, the surface hardness of Ti6AI4V alloy can reach 935HV, showing strong wear resistance. Liquide-phase ion electrolytic carbon-nitrogen co-permeation technology can also be used to treat Ti6Al4V alloy and produce a hard coating of Ti deposition on the surface of the alloy. By increasing the time of treating titanium alloy with this method, the thickness of the hard permeation layer can be effectively increased, and the wear resistance of titanium alloy can be improved.

Surface Coating Technology

       By using corresponding processes on the surface of the substrate material, composite coatings and substrate materials are used to produce a protective coating on the surface of the substrate, which has good performance in chemistry, thermology, etc. The corrosion resistance and heat resistance of surface coatings can be used to reduce production costs and improve product performance, and also have a longer service life in subsequent use. Currently, surface coating technologies such as vapor deposition and cladding can effectively improve the wear resistance of titanium alloy and have a strong effect on corrosion resistance. By integrating surface activation and hydrogenation treatment organically, the surface conductivity of titanium alloy can be effectively improved, and material corrosion problems can be avoided after contact with soft rainwater, for example. By using vapor deposition technology, TA2 and TC11 substrates can be made into TiAIN film layers, which can form a metallurgical bond of three elements combined with each other in the part where the film layer and the substrate are combined, effectively enhancing various properties of the substrate material.