Microstructure of metallic layers sintered on nitride ceramics depending of the chemical composition of interlayers

The effects of oxygen and titanium contents in the reactive layer deposited on nitride ceramics on the wettability and sintering capability of the metallic layers were examined. The deposited metallic layers were standard Mo and Mn layers with the oxygen content ranging from 0 to 40 at.% and the titanium content from 0 to 8 at.%. The layers were sintered at a temperature between 1573 and 1653 K in a hydrogen atmosphere (dew point -203 K). In the transition layers, between the Al2O3 or AlN ceramic material and the metallic layer, a continuous glass layer is formed on the ceramic surface, which wets very well both the substrate and the metallic powders. The microstructure of the metallic layers was examined using a scanning electron microscope and the electron probe. It has been found that both Al and Si migrate strongly to the interface layer. The microstructure of metallic layers sintered on AlN differs from that of the layers sintered on alumina ceramics. The interface layer formed between the ceramic material and the metallic layer, a continuous glass layer forms on the ceramic surface; the glass wets very well both of substrate and the metallic powders. The metallic layer is compact, and the solder does not flow in-between the grains. Based on results of the microstructural examinations, the mechanisms of the sintering of Al and AlN ceramics are compared. (author)