η相粉末的加入对WC-10Co硬质合金组织与性能的影响

Effect of η phase powders addition on the microstructure and properties of WC-10Co cemented carbides

通过向WC-10Co混合粉末中加入2%和4%质量分数的η相粉末和等摩尔量的炭黑,经过传统的粉末冶金工艺制备含板状WC晶粒的硬质合金,研究η相碳化反应过程以及η相粉末加入量、η相粉末在基体中球磨时间对合金组织与性能的影响。结果表明：加入少量的η相粉末及等摩尔量的工业炭黑后,WC-10Co中的WC晶粒出现了明显的板状特征,随η相粉末加入量增多,板状WC晶粒数量增多;在总球磨时间不变的前提下,随η相粉末在基体中球磨时间增加,板状WC晶粒的分布越来越均匀。所得到的板状WC晶粒是η相在950-1 200℃之间与WC-Co基体中扩散来的C原子碳化反应后生成不同形貌的WC孪晶得来的,且碳化速度是影响WC孪晶形貌的关键因素。相对于相同Co含量的传统硬质合金,板状WC晶粒均匀分布的硬质合金密度基本保持不变,硬度提高0.7%,强度提高6%,断裂韧性提高17%。

WC-Co cemented carbide with plate-like WC grains was prepared by adding 2%, 4% η phase powders and the equimolar carbon black to a ball-milled WC-10 Co batch through traditional powder metallurgy process. The carbonization reaction of η phase, effect of addition amount and the milling time in the batch of η phase powders on the microstructure and properties of cemented carbide were studied. The results indicate that small additions of η phase and equimolar carbon black help the development of plate-like grains, the number of plate-like WC grains increases as the amount of η phase powders increases, and when the total milling time is constant, the distribution of plate-like WC grains is more uniform as the milling time in the batch of η phase powders increases. This kind of plate-like WC grain is produced from the twined WC which forms from the carbonization reaction between 950 ℃ to 1 200 ℃ of η phase and the C atoms that spread from the matrix, and the carbonization rate of η phase is the key factor that influence the morphology of twined WC. The density of the cemented carbide with plate-like WC grains is the same as the traditional one which has the equal content of Co, while the hardness, transverse rupture strength, and fracture toughness are increased by 0.7%, 6% and 17%, respectively.