碳化钨粉末中晶粒抑制剂固溶量XRD对标评价方法

XRD Benchmark Evaluation Method for Solid Solution Content of Grain Inhibitors in Tungsten Carbide Powder

在细颗粒氧化钨或钨粉中添加晶粒抑制剂制取含抑制剂的碳化钨粉末是制备超细硬质合金的一种方法。通常认为WC粉末中抑制剂或固溶于WC或独立存在,但由于添加量过少,难以通过检测手段判定其存在形式及固溶量。本文尝试采用对标评价的方式建立量化指标以判断粉末中晶粒抑制剂的固溶程度,评价了添加不同质量Cr及Cr、V混合晶粒抑制剂制备的细颗粒及超细颗粒WC粉末。测试结果表明,难以判定抑制剂固溶量是因为忽略了生产中出现的缺碳相及相应的固溶产物相。评价方法以W_(2)C、(W,Cr,V)_(2)C及WC为对标对象,判断固溶量;以衍射峰峰位及半高宽为对标指标,弱化其他干扰晶格常数变化因素的影响,如谱峰较少导致的晶型不确定、工艺参数或抑制剂添加导致的结晶程度变化。相同碳化工艺、抑制剂添加量1%的范围内,粉末的(W,Cr,V)_(2)C及WC的峰位均随Cr抑制剂添加量的增加而增大,(W,Cr,V)_(2)C峰面积也有逐渐增大的变化趋势。用试样粉末制备硬质合金并测量WC晶粒度,部分结果显示其趋势与量化指标相同。

Adding grain inhibitors to fine tungsten oxide or tungsten powder to produce tungsten carbide powder containing inhibitors is a method for preparing ultrafine cemented carbides.It is generally believed that inhibitors in WC powder are either solidly soluble in the WC phase or exist as independent phases.However,due to the small amount added,it is difficult to determine its phase or solidsolution content through examining methods.This article attempts to establish quantitative indicators through benchmark evaluation to determine the degree of solid solution of grain inhibitors in powders,and evaluates the fine and ultrafine WC powders prepared by adding different amounts of Cr and Cr,V mixed grain inhibitors.The test result indicates that difficulty in determining the solid solution amountis due to the neglect of the carbon deficient phase and corresponding solid solution product phase during production.The evaluation method uses W_(2)C,(W,Cr,V)_(2)C and WC as benchmark objects to determine the solid solution amount.The diffraction peak position and full width at half max imumare used as benchmark indicators to weaken the influence of other factors that interfere with lattice constant changes,such as uncertainty of crystal type caused by fewer spectral peaks,and changes in crystallization degree caused by process parameters or inhibitor addition.Within the range of 1%inhibitor addition,the peak positions of(W,Cr,V)_(2)C and WC in the powder increase with the addition of Cr inhibitor,and the peak area of(W,Cr,V)_(2)C also shows a gradually increasing trend.Sample powders are prepared as cemented carbide and measured for WC grain size,and some results show that the trend is consistent with quantitative indicators.