Formation of W layers on SiC ceramics. Report 1: Study on EB-PVD

Abstract

As an effective method for the bonding of heat-resistant SiC/SiC composite material, the formation of W layers on the surface of SiC was studied. Because the ambient gas pressure, when the gas is contaminated with impurities, has a serious effect on the coated layer, an EB-PVD (Electron Beam-Physical Vapor Deposition) apparatus was newly developed and the characteristics of coated layers were examined. The powder of W was deposited on a porous SiC substrate. The W particles forming the layer were observed with SEM (Scanning Electron Microscope). The W layer composed of fine W particles whose diameter was uniform, was obtained by the deposition at low beam current, keeping a certain distance between the substrate and the crucible. The surface of test specimens was examined by EDX (Energy Dispersed X-ray spectrometer) analysis. The results indicated clear peaks corresponding to both M and L X-rays of W but no peaks corresponding to Si and C of the substrate. The thickness of the layer used was concluded to be sufficient for EDX analysis. In addition, it is confirmed from the cross-sectional observation of W coated layer by SEM that a W layer with a thickness of 2 micrometers is formed in 10 seconds.

耐熱物質であるSiC/SiC複合材料を接合する有効な方法として、SiC表面へのW層の形成を調べた。環境ガス圧は不純物の汚染により被覆層に大きな影響を与えるので、新たにEB-PVD(電子ビーム物理蒸着)装置を開発し、被覆層の特性を調べた。多孔質SiC基板上にW粉末を蒸着した。SEM(走査電子顕微鏡)観察を適用して層を構成するW粒子を観察した。坩堝から距離をおき、低ビーム電流の下で蒸着することで粒子径が均一で細かいW粒子層を得た。試料表面をEDX(エネルギー分散型X線分光)分析した。WのMおよびL系列のピークは明瞭であったが、基板のSiおよびCピークは無かった。EDXに対して十分な厚さの層を用いたと思われた。さらに、W被覆層の断面をSEM観察し、厚さ2μmのW層を10秒間で形成できることを確認した。