Si₃N₄/Ni接合体の破断強度に及ぼす硫酸水溶液の影響

抄録

The nickel metal joined to silicon nitride ceramics using silver-copper-titanium brazing and titanium filler was placed in a sulfuric acid solution at 323K for up to 214h. Joining strengths were measured by the 4-point bending test. Microstructures of the reaction layer and porous layer were investigated with a scanning electron microscopy and an electron probe microanalyzer. Fracture strength of the normal joint was 245MPa before soaking and decreased to 170MPa after 16h and to 100MPa after 144h in 1N H₂SO₄. Three regions were observed on the fracture surface: the region I at the reaction layer/brazing layer interface, the region II at the bonding interface neighborhood in porous layers (in silicon nitride) and the region III at the silicon nitride/reaction layer interface. In the porous layer of the silicon nitride was formed yttrium-oxide and aluminium-oxide elute by the soaking the sintering aid in the grain boundary of silicon nitride. The growth of the porous layers occurred on the joint surface of silicon nitride ceramics with different roughness due to the ground surface roughness of the test piece. The wedge-shaped porous layers were formed a residual stress on the interfacial side of the silicon nitride ceramics joints.