Solid State Diffusion Bonding of Silicon Nitride Using Vanadium Foils

Abstract

This paper describes the relation between the interfacial microstructure and the fracture strength of the joints of silicon nitride (Si 3 N 4 ) and vanadium (V) formed by solid state diffusion bonding. At first, the interfacial microstructure and its evolution process were analyzed in detail. The phase sequence at the interface changes with the bonding time showing five typical stages. In the first stage, a V 3 Si layer and V 2 N grains are formed. The V 2 N grains contact with the V 3 Si layer at 1473 K and below, while the contact is prohibited at 1498 K and above. The Si 3 N 4 /V 3 Si interface is metastable. In the second stage, a V 5 Si 3 N 1ÀX layer appears. In the third stage, V is annihilated. In the fourth stage, the V 3 Si layer is annihilated and VN grains are formed. In the fifth stage, V 2 N is annihilated. This evolution process of the interfacial microstructure agrees well with the proposed chemical potential diagram, except the metastable state of the interface. The increase and decrease behavior in the thickness of each reaction product interact with each other. The behavior of the V 3 Si layer is affected not only by the formation and growth of the V 5 Si 3 N 1ÀX layer but also by the formation of a V(Si) zone at the V 3 Si/V interface. The formation of the V 5 Si 3 N 1ÀX layer starts when the spatial gradient of the chemical potential of vanadium in the V 3 Si layer decreases to a certain value. The fracture strength of the joints changes depending on the bonding temperature and time. The higher bonding temperature leads to the higher maximum fracture strength. The maximum strength at each bonding temperature is achieved when the thickness of the V 3 Si layer is 2.0 mm. The prolonged bonding time gradually reduces the fracture strength down to 42 MPa.

A Cu–Pd–V System Filler Alloy for Silicon Nitride Ceramic Joining and the Interfacial Reactions

“…The chemical reactions at high temperatures between Si 3 N 4 and element V are complex so that different reaction products have been reported in some references under different experimental conditions . Maeda et al . reported that in the system of Si 3 N 4 –V–Si 3 N 4 under a bonding condition of 1473 K/60 min/140 MPa, not only V 3 Si but also V 2 N were formed at the interface, and with the increase of bonding temperature and the prolonging of bonding time, besides V 3 Si and V 2 N, new reaction products of V 5 Si 3 N 1−x and VN appeared in the joint.…”

Microstructure of SiC / TiAl Interface Formed by Solid-State Diffusion Bonding

“…The actual phase sequences at the bonding temperatures were verified on the basis of the Ti-Al-Si-C quaternary chemical potential diagram. The diagram describes the relation between the phase equilibria and the chemical potential of each constituent element [10], being suitable for describing phase sequences of diffusion-bonded interfaces [11,12]. Fig.…”

Microstructural and mechanical characterization of the Si3N4/Si3N4 joint brazed using Au–Ni–V filler alloys

“…Previous studies showed that the Si 3 N 4 /Si 3 N 4 joints with high thermal and oxidation resistance can be achieved by adding metals such as Au, Pd, Ni, and V into the filler alloys. [5][6][7] In this study, two Au-Ni-V metals in the form of foils were used as filler alloys for brazing Si 3 N 4 ceramic. The microstructure and mechanical properties of the Si 3 N 4 /Si 3 N 4 joint were studied, and the bonding mechanism was discussed with reference to the discovered phases in the joint and brazing parameters.…”