Abstract

Bonding of Si3N4 to refractory metals has been investigated using liquid insert metals of copper base alloys. The bonding has been carried out in an electric furnace in vacuum of 6 mPa. Strength of joints was evaluated by tensile-shear tests made at temperature from room temperature to 1073 K.Copper-Haynes No. 188 alloys which showed good wettability with Si3N4 were selected as an insert metal. Strength obtained for joints of Si3N4 to Si3N4, tungsten, molybdenum, niobium and tantalum were about 160 MPa, 80 MPa, 100 MPa, 60 MPa and 55 MPa, respectively. Strength of joints of Si3N4 to tungsten and molybdenum increased with the rise of test temperature from room temperature to 473 K and reached 90 MPa and 100 MPa, respectively.In the joint of Si3N4 to Si3N4, voids were observed' in the insert layer except for the insert metal of copper with 20-30%Haynes No. 188 alloys. Liquidus and solidus temperature of insert metals decreased with increasing copper content. The improved fluidity of the insert metal caused by the decrease in the melting temperature seemed to have the effect of preventing the void formation in the insert layer, resulting in improvement of the strength of the joint.

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