Reactive Magnetron Sputtering (ti, Al) N Films

In this article, the development of vapor deposition of superhard films and the structure, properties and applications of TiN series superhard films were described briefly at first. The advantages of (Ti,Al)N films and the key points of future research were analysed. Based on this, advanced ternary (Ti,Al)N films were produced on WC-6%Co and stainless steel substrates respectively by reactive direct current ( D.C.) magnetron sputtering technique. Different microstructures and properties of these films were obtained under various values of nitrogen flow rate and substrate temperatures. The effect of substrate bias voltages on morphologies and properties of the films was also investigated. X Ray Diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), and Micro-hardness Detector measurements were used to observe and analyse the microstructures, micro-morphologies and properties of the films. By discussion, the following conclusions can be achieved.l)(Ti,Al)N films were produced when the substrate temperature was varied from 250癈 to 400癈, the deposition pressure is between 1.0~ 1.3Pa, the flow rate ratio of N2/Ar is less than 1:1. The composition of the films was identified as Ti3AlN.2)An obvious (111) texture was observed when the flow rate ratio of N2/Ar is low, and the intensity of the texture decreased as the flow rate ratio of N2/Ar increased.3)Changes of micro-morphologies and surface roughness of the films were obvious: as the flow rate ratio of N2/Ar increased, the grain size and surface roughness decreased first, and then increased slightly; however, the micro-hardness increased first, and then decreased a little as the flow rate ratio of N2/Ar increased. When the flow rate ratio of N2/Ar was 1:2, the optimum quality of the films was achieved with the smallest grain size and surface roughness value, and the top micro-hardness.4)There is a threshold value in the flow rate of nitrogen. When the flow rate ratio of N2/Ar is no less than 1:1, the (Ti,Al)N films can not be produced because of the decreasing pressure of argon and target poison.Abstract5)The substrate temperature influence the texture and micro-hardness little in a range of 250~400. However, as the temperature increased, the micro-morphologies changes obviously: the vaulted morphology grains disappeared and the surface roughness decreased.6)Obvious changes of microstructures and micro-morphologies of the films were caused under various substrate negative bias voltages. When the negative bias voltages was varied from 0V to -125V, the surface roughness and grain size decreased for the enhancement of the transfer ability and diffusion ability of the deposition ions caused by negative bias voltage weakened the influence of temperature rising caused by bombardment. In this study, best films can be obtained at values between -125V and -150V. When the negative bias voltages were varied from -125V to -150V, the grain size of the films increased, for the influence of temperature rising caused by bombardment is the dominating effect. When the bias voltage is beyond -200V, we can not produce (Ti,Al)N films because of the exorbitant internal stress.