Takatoshi Oshika

A study of the adhesion between CVD layers and a cemented carbide substrate by AEM analysis

Abstract The interface between chemical vapor deposition (CVD) coated layers and cemented carbide substrate of coated cemented carbide inserts was analyzed by analytical electron microscopy (AEM). This analysis was carried out from the viewpoint of the adhesion of the coated layer. From the results of elemental analysis, it became clear that the amounts of W and Co diffused from the substrate into the coated layer were different among three coating conditions. A columnar TiCN grain produced in relatively low temperature scarcely contained these elements, and they were detected only at the grain boundary. On the other hand, these elements diffused inside the grains when the shape of the grain was granular as TiN. Strong adhesion of coated layer was obtained when a proper amount of these elements was diffused. Coated inserts containing an interfacial layer with suitable diffused materials and main columnar TiCN layer showed good cutting performance.

CVD Material Processing. Unveiling the Magic of H2S on the CVD-Al2O3 Coating.

CVD-Al2O3層は基体上で均一な層厚の被膜を得にくい等の問題がある. これはCVD反応ガス中に微量のH2Sを添加することで改善されるが, その機構は明らかになっていない. 本研究ではH2Sの添加がCVD-Al2O3反応の均一被覆性向上に及ぼす影響を, 気相に存在する粒子に焦点を当て考察した. 気相中の直径200nm以上の微粒子個数濃度をパーティクルセンサーで計測した結果, H2Sがない場合108/m3以上だった微粒子濃度が, H2S添加量の増加と共に減少し, 0.20%の添加でバックグラウンドレベルの106個/m3以下になった. H2SによるCVD-Al2O3成膜プロセスの改善は, 気相中Al2O3前駆体のサイズダウンによる拡散係数の増大が影響していると考えられる.