WC−Ni3Al−B composites prepared through Ni+Al elemental powder route
(1. State Key Laboratory of Cemented Carbide, Zhuzhou 412000, China;
2. Zhuzhou Cemented Carbide Group Corp. Ltd., Zhuzhou 412000, China)
2. Zhuzhou Cemented Carbide Group Corp. Ltd., Zhuzhou 412000, China)
Abstract: In order to develop the liquid phase sintering process of WC−Ni3Al−B composites, the preparation process of WC+Ni3Al prealloyed powder by reaction synthesis of carbonyl Ni, analytical purity Al and coarse WC powders was investigated. DSC and XRD were adopted to study the procedure of phase transformation for the 3Ni+Al and 70%WC+(3Ni+Al) mixed powders in temperature ranges of 550−1200 °C and 25−1400 °C, respectively. The results demonstrate that the formation mechanism of Ni3Al depends on the reaction temperature. Besides WC phase, there exist Ni2Al3, NiAl and Ni3Al intermetallics in the powder mixture after heat treatment at 200−660 °C, while only NiAl and Ni3Al exist at 660−1100 °C. Homogeneous WC+Ni3Al powder mixture can be obtained in the temperature range of 1100−1200 °C. The WC−30%(Ni3Al−B) composites prepared from the mixed powders by conventional powder metallurgy technology show nearly full density and the shape of WC is round. WC−30%(Ni3Al−B) composites exhibit higher hardness of 9.7 GPa, inferior bending strength of 1800 MPa and similar fracture toughness of 18 MPa·m1/2 compared with commercial cemented carbides YGR45 (WC−30%(Co−Ni−Cr)).
Key words: WC−Ni3Al−B composites; Ni3Al intermetallic; liquid phase sintering; mechanical properties