Reaction products and growth kinetics during diffusion bonding of SiC ceramic to Ni–Cr alloy

Abstract

Vacuum diffusion bonding of SiC ceramic to Ni–25 at.-%Cr alloy was carried out at 1223–1323 K for 0.9–3.6 ks under a pressure of 7.2 MPa. The kinds of the reaction products and the interface structures of the joints were investigated by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and X-ray diffraction (XRD), and the kinetic parameters describing the growth of reaction layers were calculated. The experiment and analysis identify that four kinds of reaction products, namely Ni₂Si, graphite (G), Ni₅Cr₃Si₂ and Cr₃Ni₂SiC, have formed during the diffusion bonding of SiC ceramic to Ni–25 at.-%Cr alloy. The interface structure of the SiC/Ni–Cr joints is SiC/(Ni₂Si+G)/(Cr₃Ni₂SiC + Ni₅Cr₃Si₂)/Ni₅Cr₃Si₂/Ni- Cr, and each reaction layer in this structure grows according to a parabolic law. The activation energies for growth of (Ni₂Si+G), (Cr₃Ni₂SiC+Ni₅Cr₃Si₂), and Ni₅Cr₃Si₂ are 217, 248, and 233 kJ mol ­ 1, respectively.