Wetting and Brazing of Chromium Film-Deposited Alumina Using AgCu Filler Metal

Wetting behavior of AgCu filler on chromium film-deposited Al2O3 ceramics was studied by sessile drop method under vacuum, and brazing of chromium-deposited alumina using AgCu was carried out. Cr film can improve the wettability of AgCu filler on alumina ceramics, and the contact angle decreased dramatically. However, with further increase in temperature and extension of wetting time, Cr atom might diffuse excessively to molten alloy or substrate leading to thinned or disappeared Cr film on alumina; thus, the contact angle of AgCu on alumina increased. The reliable alumina joint was obtained via chromium deposition using AgCu filler brazed at 900 °C for 10 min, and no hard or brittle intermetallic compounds formed in the brazed joint. The maximum shear strength of 16.8 MPa was achieved when the thickness of deposited chromium film was 2 μm.