Fe-N-Co系合金Kovar表面酸化物の電子回折的研究

抄録

In order to study the adhesiveness of Kovar (54% Fe, 29% Ni, 17% Co, γ-phase at room temperature) to glass for making aiγ-tight joint, structure and surface oxidation products of the alloy are investigated by electron and X-ray diffraction methods and optical micro-scopy.
As is well known, γ-phase (f.c.c., a₀=3.54 Å) of Kovar is easily transformed to α-phase (b.c.c., a₀=2.84 Å) by cold works such as mechanical polishing and rolling. It is found that a cold-rolled specimen, which is composed of γ- and α-phases, produces electron-diffraction patterns of only γ-phase when polished electrolytically, indicating that α-phase dissolves out selectively.
By such procedures surfaces varying in amounts of α-and γ-phases are prepared and their surface oxidation products are examined. The surface composed of γ-phase produces spinel type oxide and that of α-phase produces hematite type oxide below 500°C. At higher temperatures (above 600°C) both kinds of surfaces produce spinel type oxide. As it has been mentioned, the existence of spinel type oxide favours the metal to glass adhesion. But it is not the necessary condition since, even under the condition to produce hematite type oxide, fairly good joints are obtained.