Abstract
Liquid-phase sintering of Cr 3C 2/NiCr cermets was investigated as a function of Cr 3C 2 content (55–95 wt%) at a constant Ni-to-Cr ratio of 4. Specimens cold-isostatically pressed at 230 MPa were sintered in a vacuum and in the presence of a liquid phase, at 1300°C for 15 and 30 min. Specimens with a carbide content of <75% were heavily distorted due to excessive liquid phase formed during sintering, but those with a higher carbide content were densified to near theoretical density (>98%) within 15 min. The density of the succesfully sintered specimens decreases slightly with inreasing carbide content and sintering time. Using X-ray diffraction analysis and scanning electron micrographs, it was revealed that the microstructures consisted of a prismatic Cr 3C 2 phase and a metallic binder phase. The hardness of the samples increased with increasing carbide content, whereas the transverse rupture strength decreased. The decrease in strength is attributed to the reduction in the metallic binder content and to poor densification. It was shown that almost fully-densified Cr 3C 2/NiCr cermets with carbide contents of 75–95 wt% could be produced in a vacuum through the liquid-phase sintering process at a low temperature, such as 1300°C, for a sintering time as short as 15 min.
Published Version
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