Pt催化作用下无氢碳化制备纳米WC粉及其烧结性能研究

Preparation and sintering properties of nano WC powder by Pt catalyzed hydrogen-free carbonization

摘要:

针对无氢碳化中反应速率缓慢、颗粒长大的问题,在无氢碳化过程中添加少量Pt作为催化剂,制备纳米WC粉。采用热压烧结对WC粉进行烧结得到无粘结相硬质合金。研究了Pt添加对WC粉的形貌和烧结性能的影响,以及Pt和烧结温度对烧结样品的致密化,组织和力学性能的影响。结果表明,少量的Pt可显著降低无氢碳化温度,制备的WC粉粒径细小且均匀。随着烧结温度升高,无粘结相硬质合金的致密度增加,晶粒尺寸增大,硬度与断裂韧性增加,但烧结温度过高,出现异常长大晶粒和W₂C,导致无粘结相硬质合金的断裂韧性严重下降。最佳烧结工艺为,烧结温度1700 ℃,保温60 min,压力40 MPa,所得无粘结相硬质合金致密度达到98.8%,平均晶粒尺寸为263.6 nm,维氏硬度和断裂韧性分别为2887 kg.mm^_-2和7.1 MPa.mm^_1/2。

Abstract:

In order to solve the problem of slow reaction rate and particle growth in hydrogen-free carbonization, a amount of Pt (0.01 wt%) was added as catalyst in the carbonization process to improve the reaction rate and prepare nano WC powder.The binderless tungsten carbide was produced by hot press sintering (HPS) at 1400-1800 ℃ with an applied pressure of 40 MPa.The effects of Pt addition on the sintering performance and microstructure WC powder and the effects of Pt addition and the sintering temperature on the densification, microstructure and mechanical properties of the sintered sample were investigated.The results show that a amount of Pt (0.01 wt%) can significantly reduce the temperature of hydrogen-free carbonization, and the prepared WC powder has a fine and uniform particle size.As the sintering temperature increases, the density of binderless tungsten carbide increases, the grain size increases, and the hardness and fracture toughness increase. However, when the sintering temperature is too high, resulting in abnormal growth grains and W₂C phase, which leads to a serious decline in the fracture toughness of binderless tungsten carbide. When the sintering tempertuare was 1700 ℃, the hardness and fracture toughness reached the maximum walues of 2887 kg.mm^_-2 and 7.1 MPa.mm^_1/2, respectively.