Ni+Al元素粉末法制备WC-Ni3Al-B复合材料

摘要

为发展WC-Ni3Al-B复合材料的液相烧结制备技术,研究由羰基Ni粉、分析纯Al粉和粗WC粉的混合粉末反应合成制备的WC+Ni3Al预合金粉末.采用DSC和XRD分别研究3Ni+Al和70％WC+(3Ni+Al)混合粉末在550～ 1200 ℃和25～1400℃温度范围的相变过程.结果表明:Ni3Al相的形成取决于反应温度.在200～660 ℃热处理温度范围内,除了WC相外,还存在Ni2Al3、NiAl和Ni3Al相；而在660～1100 ℃温度范围内,仅存在NiAl和Ni3Al相;在1100～1200℃温度范围可以获得均匀的WC+Ni3A1预合金粉末混合物.采用该预合金粉末制备的WC-30％(Ni3Al-B)复合材料具有很高的致密度,且WC晶粒呈圆形.与普通商用YGR45(WC-30％(Co-Ni-Cr))相比,WC-30％(Ni3Al-B)复合材料具有更高的硬度(9.7 GPa),低的抗弯强度(1800MPa)和相近的断裂韧性(18MPa·m1/2).%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 ℃ and 25-1400 ℃,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 ℃,while only NiAl and Ni3Al exist at 660-1100 ℃.Homogeneous WC+Ni3Al powder mixture can be obtained in the temperature range of 1100-1200 ℃.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)).