A novel preparation method for W–Cu composite powders

Abstract

A novel method of nitridation-denitridation was developed to prepare W–Cu composite powders. The preparation process consists of calcination, nitridation and denitridation, and the performance of W–Cu composite powders mainly depends on nitridation–denitridation process. When the nitridation is carried out in ammonia at 450 °C for 3 h, the phases of CuWO4−X, WO3 and CuO transform to WO3-X and Cu. While the temperature reaches 550 °C, the phase of W2N appears, and it's further increase to 650 °C or even higher leads to only W2N and Cu exist in products. A small quantity of W2N is observed during the process of denitridation occurs in hydrogen at 825 °C for 2 h. When the denitridation temperature is above 850 °C, the patterns only contain peaks corresponding to W and Cu phases. The mean particle size of composite powders decreases from 109.23 nm to 90.19 nm with the increase of denitridation temperature from 825 °C to 875 °C, and it's further increase to 900 °C results in the increase of the mean particle size of composite powders. The spherical W–Cu composite powders with the mean particle size of 90.19 nm are obtained when the nitridation temperature and the denitridation temperature are 650 °C and 875 °C, respectively. W–Cu alloys are prepared by sintering such composite powders in hydrogen at 1200 °C for 90 min, and the relative density and hardness reach 98.2% and 258.7 HV, respectively.