Effect of substrate bias voltage on the properties of arc ion-plated TiN films onto high speed steels
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Effect of substrate bias voltage on the properties of arc ion-plated TiN films onto high speed steels Syuji Yamamoto and Hiroshi Ichimura Central Research Laboratory, Sumitomo Metal Mining Co. Ltd., 3-18-5, Nakakokubun Ichikawa, 272, Japan (Received 3 May 1995; accepted 16 November 1995)
The effect of substrate bias voltage on the properties of arc ion-plated TiN films onto high speed steels has been investigated. The high density structure with a large crystallite size grew at the high bias voltage. TiN films deposited by higher bias exhibited strong preferential (111) orientation from XRD. The internal stress of TiN films increased at first with increasing substrate bias voltage; however, it decreased as the bias voltage increased over 100 V. The coating adhesion measured by the scratch tester increased with increasing bias voltage, and this is coupled with a cohesion of films. Cutting performance of TiN coated drills, which increased markedly with increasing substrate bias, has been studied in relation to the physical and chemical properties of deposited films.
I. INTRODUCTION
Because of its exceptional wear resistance using TiN coated high speed steels for cutting tools and forming tools increases tool life by several hundred percent. Many researchers have reported the fabrication and characterization of TiN coating produced by various preparation techniques, including chemical vapor deposition (CVD) and physical vapor deposition (PVD) such as reactive sputtering and ion plating. Of these techniques, ion plating has the advantage that it is an inexpensive process and provides good crystalline film fabrication and high adhesion to metal substrate. The expected performance of the coated products can be achieved if the adhesion and the intrinsic cohesion of the coating film itself are sufficient. In the PVD process, there are various processing conditions that influence the properties of the coating parts. The more important variables are (i) substrate bias voltage, (ii) substrate temperature, (iii) reactive gas pressure, (iv) evaporation-deposition rates, (v) source-to-substrate distance, and (vi) substrate geometry. These process variables and the complex plasma species interactions must be considered to deposit the films with the desired properties. In the ion-plating process, the substrate bias markedly affects the mechanical properties of coatings. The effect of substrate bias on the physical properties of films that deposited onto metal substrates using ion plating has been reported by many authors.1–3 The relationship among substrate bias voltage, physical properties, and wear resistance, however, is far from being fully understood. Mechanical strength of PVD films strongly depends on morphology, internal stress, and adhesion to substrate. The levels of internal stress present in a deposited film are important since they often relate to coating J. Mater. Res., Vol. 11, No. 5, May 1996
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