A novel preparation method for W-Cu composite powders

摘要

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 degrees C for 3 h, the phases of CuWO4-X, WO3 and CuO transform to WO3-X and Cu. While the temperature reaches 550 degrees C, the phase of W2N appears, and it's further increase to 650 degrees 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 degrees C for 2 h. When the denitridation temperature is above 850 degrees 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 degrees C to 875 degrees C, and it's further increase to 900 degrees 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 degrees C and 875 degrees C, respectively. W-Cu alloys are prepared by sintering such composite powders in hydrogen at 1200 degrees C for 90 min, and the relative density and hardness reach 98.2% and 258.7 HV, respectively. (C) 2015 Elsevier B. V. All rights reserved.