CVD 法で被覆した TiC 膜の残留応力と強度評価に関する X 線的研究(<特集>X 線材料強度)

概要

論文の詳細を見る
Thin films of titanium carbide (TiC) were coated on various substrates such as cemented carbide (WC-Co) with different cobalt contents, ferritic and austenitic steels by the chemical vapor deposition (CVD) method. Thin films did not have strong texture. The residual stress in thin films was measured by the sin^2Ψmethod of X-ray stress measurement. The residual stress was tensile for WC-Co substrates, while compressive for steel substrates. The residual stress was nearly uniform within the film thickness for the cases of WC-Co substrates, while it had rather steep distribution for the cases of steel substrates. The magnitude of the residual stress increased in proportion to the mismatch of the coefficient of thermal expansion (CTE). The measured stress was more compressive than the prediction by CTE mismatch. Under the uniaxial applied stress, the stress in the thin film was biaxial because of the mismatch of Poisson's ratio, and increased in proportion to the applied strain as predicted from the elasticity relation of coated layers. At high applied strains, the stress in the thin film measured by X-rays did not increase because of cracking. The tensile fracture strength of TiC films on WC-Co substrates was found to be around 750 to 800MPa. This value is about twice the fracture strength of bulk materials.
社団法人日本材料学会の論文
2003-07-15