碳量及B类孔隙对WC-8%Co硬质合金抗弯强度的影响

采用粉末冶金方法制备了WC-8%Co硬质合金试样,经氢气烧结后,利用钴磁测试仪、强度测试仪、电子显微镜和金相显微镜分别对试样的钴磁和抗弯强度进行测定、对试样断口和金相缺陷进行观察。研究了WC-8%Co硬质合金抗弯强度与碳量(相对磁饱和)、金相缺陷(B类孔隙)之间的关系。结果表明:将试样碳含量及孔隙度控制在一定的范围内,可以使试样抗弯强度保持在较高的水平,当试样相对磁饱和为88%~92%,B类孔隙为B00时,合金显微组织中WC晶粒较为均匀,无异常长大情况,WC-8%Co硬质合金抗弯强度可达3 286 N/mm2;同时,抗弯强度值的大小随孔隙度的增多而下降。另外,氢气烧结后经HIP处理可以有效消除WC-8%Co硬质合金中的孔隙缺陷,从而提高合金抗弯强度,经HIP处理的试样的强度比正常样的强度高出2.3%。

Effects of Carbon Content and B Class Porosity on Bending Strength of WC-8%Co Cemented Carbide

WC-8%Co cemented carbide specimens were prepared by powder metallurgy method.The cobalt magnetism and bending strength of the specimens were tested.The fracture surface and the defects in the microstructure were observed.Furthermore the effects of the carbon content(relative magnetic saturation) and the defects(B class pores) on the bending strength of the cemented carbide were studied.The results show that by means of controlling the carbon content and the porosity in the certain ranges,the bending strength of the WC-8%Co cemented carbide remains at a high level.When the relative magnetic saturation is in the range of 88%-92% and the metallographic B class porosity is B00,the WC grain size of WC-8%Co is more uniform and the bending strength of the cemented carbide reaches its highest values at 3 286 N/mm 2.Meanwhile,the bending strength value decreases with the increasing of porosity.In addition,HIP treatment after hydrogen sintering can effectively eliminate pore defects in the WC-8%Co cemented carbide,thus the bending strength is enhanced up to 2.3%.