Titanium Aluminum Nitride Coatings Research Articles

Thermodynamic Modeling of the Ti-Al-N System and Application to the Simulation of CVD Processes of the (Ti,Al)N Metastable Phase

Owing to its numerous technological applications in the fields of integrated circuits and protective coatings, the TiAlN system has aroused increasing interest. The purpose of this paper is to propose a thermodynamic model and simulate its processing conditions. The calculation and optimization of the TiAlN ternary phase diagram was performed as the first step to modeling two competitive CVD processes used for the processing of titanium aluminum nitride coatings: low pressure chemical vapor deposition (LPCVD) and metal-organic chemical vapor deposition (MOCVD). Thermodynamic simulations of the processes have been used to investigate the effect of varying operating parameters and to predict the nature of the phases present at equilibrium. Calculations were then made on the TiAlNClHAr and TiAlNCHAr chemical systems, corresponding to the two CVD processes.

The mechanical and tribological properties of titanium aluminium nitride coatings formed in a four magnetron closed-field sputtering system

Titanium aluminium nitride coatings have been deposited onto rotating tool steel substrates of three different roughnesses using four unbalanced rectangular planar magnetrons arranged in a closed field configuration. Three of the magnetrons were fitted with titanium targets and the fourth with aluminium. By varying the magnetron powers and the speed of substrate rotation, coatings of chosen composition can be deposited as either multilayers or homogeneous alloys. The composition and morphology of the films have been investigated using X-ray diffraction and scanning electron microscopy, and their mechanical properties have been characterised by scratch testing and microhardness measurement. The tribological properties have been established by pin on disc testing against hemispherical tungsten carbide pins, using relocation profilometry to provide accurate measurements of wear depths less than the original surface roughness. Good correlation of the mechanical and tribological properties is reported.

Tribological characterisation of hard carbon films produced by the pulsed vacuum arc discharge method

Hard diamond-like carbon (DLC) films were deposited on silicon and high-speed steel substrates using a pulsed vacuum arc discharge method. The plasma plume was focused on the substrate using a direct electromagnetic coil. Several methods were used for coating characterisation. The film composition was analysed using Rutherford backscattering spectroscopy and forward recoil spectroscopy. About 0.5 at.% oxygen and about 1 at.% hydrogen was detected in the film. The tribological properties of the carbon films were studied using pin-on-disc tests. The counterface materials employed were alumina and hardened steel (AISI 52100 and M50) pins, which were slid against the coated substrates. The friction coefficient was measured and the wear surfaces were studied. The sliding speed was in the range 0.02–0.6 m/s and the load in the range 5–20 N. The tests were carried out in air with a relative humidity of 50±2% and at a temperature of 24±3 °C. The test results show that the DLC coatings produced for this study generally had a coefficient of friction (μ) of about 0.2. The lowest value measured was μ=0.14. The wear resistance of the coatings was good, provided that the adhesion to the substrate was sufficient. The comparative tests with titanium nitride and titanium aluminium nitride coatings showed that DLC films are considerably more wear resistant than titanium-based coatings.