繰返し球圧子押込み試験によるセラミック被覆超硬合金における薄膜の耐久特性評価

概要

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The purpose of this study is to investigate aspects of ceramic thin film deposited on cemented carbide under cyclic sphere indentation loading and to clarify the possibility of the sphere indentation test to evaluate endurance characterizations of ceramic thin films. Three kinds of ceramic thin films were deposited onto cemented carbide WC-Co substrates. Cyclic sphere indentation tests were carried out by using spherical indenters of varying diameter 2R to investigate the aspects of crack initiation, wear progress, and delamination in ceramic film and to obtain the influence of the applied maximum load Pmax on the cyclic number of crack initiation Ni in thin films. The main conclusions are the following. (1) Ring crack initiate at the lower load than that of a ring crack initiation load obtained by static sphere indentation test. (2) After ring crack initiate, wear of film progresses inside the contact area, and delamination in thin film occur. (3) Quantitative evaluation of wear is possible by measuring the cross-sectional shape of contact area. (3)The Pmax - Ni relationships specifically depend on the diameter of spherical indenter 2R. (4) The effect of 2R on the relationship between tensile stress of film σr,i and Ni is smaller than that of the Pmax - Ni relationship.