Mastering the technology of manufacturing TiN film on titanium alloy base, oriented to application in the orthopedic trauma industry

Surface preparation of Ti6Al4V alloy sample and Univex 400 magnetron sputtering device at Institute of Materials Science

Research on implantable materials in the field of traumatology and orthopedics

Implantable materials in the field of trauma and orthopedics are used to replace damaged or lost body parts, which improves the quality of life as well as extends the life of patients. Ti and Ti alloys show marked advantages in terms of biocompatibility, corrosion resistance and superior mechanical properties. Therefore, they are currently the most commonly used material in the biomedical field.

In Ti alloys, Ti6Al4V was the first standard alloy applied as a biomedical material and is widely used today. However, the release of Al and V ions or waste materials during abrasion not only shortens the life of the material, but also causes symptoms of inflammation and discoloration of the patient's surrounding tissues. To solve this problem, it is urgent to find a coating film for Ti6Al4V alloy materials that meet the requirements of wear resistance, corrosion and ensure mechanical strength so as not to be deformed when treated with sterilization, and at the same time have good biocompatibility with the human body.

Over the decades, TiN membranes have been one of the first coatings developed for implants, joint replacements and bone fixation, reducing abrasion at the joint surface and preventing contamination with metal ions. In addition, TiN coating film is also used to enhance hardness, help maintain the sharpness of medical tools such as scalpel blades, bone cutting drills, increase antibacterial ability and improve sanitary conditions. However, the use of physical vapor phase deposition to make coating films often contains defects and pores. This has caused the fabricated coating film to be limited in terms of mechanical properties and physicochemical properties.

Recently, ultrasonic surface treatments have been used to enhance film properties such as hardness, corrosion and abrasion resistance. The research results showed that after ultrasonic surface treatment at 19.6 kHz, the surface bumpiness of the film was significantly reduced, and the high density of the film improved mechanical properties and corrosion resistance, abrasives for TiN coating films.

Master the technology

Realizing the important applications of TiN coating film in many fields, which is a research direction that is strongly focused on developing in the world and new in Vietnam, Dr. Luong Van Duong and his colleagues proposed and were approved by the Vietnam Academy of Science and Technology to carry out the task of international cooperation with the Institute of Acoustics and Technology, Belarusian Academy of Sciences: "Application of ultrasonic processing to improve the properties of TiN films on biomedical titanium alloys made by physical vapor phase deposition (PVD) method" (ISBN : QTBY01.02/21-22).

In this study, samples of TiN coating films were fabricated using magnetron sputtering. In particular, the influence of sputtering capacity and N2 gas flow on the structure and properties of the studied membrane includes: phase structure, surface morphology - cross section, hardness and friction coefficient. The results of studying the effect of sputtering power show that the fabricated membrane has a single-phase structure of the face-centered cubic network. Scanning electron microscopy images indicate that the membrane has columnar crystals, along with an increase in film formation rate as sputtering capacity increases. In addition, the rigidity of the membrane reached maximum values (22.8 GPa ± 1.2 GPa) at 250 W sputtering power and the lowest coefficient of friction (0.42) at 150 W sputtering power. The scientists elucidated the influence of N2 gas flow on the structure and properties of TiN membranes. As the flow rate of N2 gas increases from 10 to 30 sccm, the faceted diffraction peak strength (111) of the TiN membrane gradually increases, and the sputtering particle shape changes from a multifaceted structure to a spherical structure. At an N2 gas flow of 25 sccm, the TiN film obtains a fine-grained structure (approx. 60 nm) along with a maximum hardness value (24.8 ± 1.8 GPa). The adhesion strength of TiN membranes at different N2 gas flows all have a critical load of > 30 N. In addition, electrochemical corrosion measurement results also show that sputtering films at different gas ratios have better corrosion resistance than biomedical titanium alloy Ti6Al4V. In addition, by ultrasonic treatment of TiN film surfaces, a number of properties such as surface bumpiness and hardness have been improved.

Dr. Luong Van Duong said: Improving the properties of TiN coating film by ultrasonic treatment can increase the service life of implanted parts. This result also creates a premise to expand the scope of application for nitride coating films in many industries and many other fields. However, further research is needed, especially to carry out biocompatibility testing studies in human pseudofluids or in animals to be able to assess compatibility to guide practical application. Therefore, scientists look forward to further developing this direction of research in the future.

Model of sputtering equipment for making TiN film

Electron microscopy scans the surface of TiN membranes at different gas flows: a) 10 sccm; b) 15 sccm; c) 20 sccm; d) 25 sccm; e) 30 SCCM

Translated by Phuong Ha
Link to Vietnamese version