Evaluation of adhesion strength for amorphous SiC thin film and DLC/a-SiC laminated thin film deposited on steel substrates for cutting tool

Abstract

This paper describes the evaluation of adhesion strength between the amorphous Silicon carbide (a-SiC) thin film, Diamond-Like Carbon (DLC)/a-SiC laminated thin film and materials used for the cutting tool. The a-SiC and DLC/a-SiC thin films were deposited on the tungsten carbide steel substrate: K10 and on the high speed steel substrate; SKH51 by Plasma-Enhanced CVD method of the hot cathode PIG discharge type. Scratch tests were carried out for examining the critical fracture load of the films. Finite Element Method (FEM) analyses were also performed to clarify the stress distribution at the interface between the films and substrates. The stress intensity factors K I and K II, and the fracture toughness Kc were calculated from results of scratch tests and FEM analyses. The K I, K II, and Kc of a-SiC and DLC/a-SiC thin films deposited on the K10 substrate were larger than those of the thin films deposited on the SKH51 substrate. The K I, K II and Kc of both of the films were directly proportional to the density of a-SiC thin films. In turning experiments, the delamination area of DLC/a-SiC thin films deposited on the cutting tool of K10 is closely related to the Kc obtained from the scratch tests and FEM analyses.