Sinter-bonding of Cr₃C₂-Ni Base Cermets onto Steel Substrates

Abstract

Ternary Cr₃C₂-Ni-WB cermets can be sintered to full density at temperatures lower than 1450K. The lower densification temperatures, compared with the Cr₃C₂-Ni system (1550K), were attributed to the liquid phase formation as the results of WB-Ni quasi-eutectic reaction prior to Cr₃C₂-Ni reaction. The bonding of the interface proceeds during the liquid phase sintering of the cermets. A direct reaction between the Cr3C2 particles and the substrate material should be avoided for a satisfactory sintered body of the cermet and sufficient interface bonding strength. In case of the cermets without WB, an excessive reaction occurred due to higher sintering temperatures than the reaction temperature at the interface. The direct reaction between the Cr₃C₂ and S45C generates a large amount of a liquid phase and causes remarkable grain coarsening of the carbides. The coarsened carbide particles were identified as a M₇C₃ type containing W and Fe.