粉末冶金法制备WC-Ni3Al复合材料的组织与性能

在WC粉末中直接添加Ni、Al元素粉末,通过在液相烧结过程中反应合成Ni3Al来制备WC-Ni3Al复合材料,对该材料进行组织结构观察及力学性能测定,分析铝含量对合金致密化和镍铝相形成种类的影响,并对材料的抗氧化性能进行测试。结果表明,制备的WC-Ni3Al复合材料具有圆钝的WC晶粒形貌,粘结相中除Ni3Al相外还有少量的NiAl和Ni相;铝含量对WC-Ni3Al材料致密度的影响主要与高熔点的NiAl的形成量有关。与普通WC-15Ni硬质合金的抗弯强度(1 900 MPa)和硬度(82.6 HRA)相比,WC-15Ni3Al复合材料具有低的室温抗弯强度和高的硬度,分别为1 170 MPa和86.5 HRA。随Ni3Al含量(质量分数)从15%增加到30%,WC-30Ni3Al复合材料的室温抗弯强度增加,而硬度降低,分别为1 660 MPa和81.7 HRA,其高温抗氧化性能比WC-30(Co-Ni-Cr)硬质合金提高1个数量级。

Microstructure and properties of WC-Ni3Al composites by powder metallurgy

The WC-Ni3Al composites were fabricated by powder metallurgy via reaction synthesis to form Ni3Al by the direct addition of Ni and Al during liquid sintering process.The microstructure and properties were observed and measured,respectively.The influences of Al content on densification and phase types of nickel aluminides were analysed.High temperature oxidation resistance was determined.The results show that WC grain of WC-Ni3Al composites has smooth topography.Besides main Ni3Al phase,there exists a small amount of NiAl and Ni phases in the binding phase.The densification affected by Al content relates to the amount of high-melting-point NiAl phase.WC-15Ni3Al composite has inferior bending strength of 1 170 MPa and high hardness of 86.5HRA at room temperature compared with WC-15Ni cemented carbide.As the content of binding phase Ni3Al increases to 30%(mass fraction),the WC-30Ni3Al composite has bending strength of 1 660 MPa and hardness of 81.7 HRA at room temperature and its high temperature oxidation resistance is about an order of magnitude higher than that of WC-30(Co-Ni-Cr) cemented carbide.