Determination of Alloy and Impurity Elements in the WC-Co Based Cemented Carbide by Microwave Digestion - Inductively Coupled Plasma Atomic Emission Spectrometry

Abstract

Using high-pressure sealed microwave heating method, the WC-Co based cemented carbide samples were digested completely by nitric acid and phosphoric acid (VHNO3: VH3PO4 = 5:1). Then the digestion solution was diluted with water to a constant volume, and directly using inductively coupled plasma atomic emission spectrometry (ICP-OES) determination of the content of 0.005 to 10% Co and 0.005 ~ 1% of Fe, Nb, Ta, V, Cr, Mo and Ni. This paper examine the best digestion conditions, including reagent composition, ratio, and microwave control parameters, etc., then establish a set of microwave digestion and by complex reactions with inorganic reagents to stabilize the high tungsten matrix digestion method, in order to quickly and completely digest the tungsten-cobalt-based samples and avoid the generation of tungsten acid precipitation resulting in the loss of some of the analyte and impact of organic complex agents on the spectral determination. The results showed that: the control parameters of using 5 min to heat the sample to 130 °C and keep for 5 min, then heated to 190 °C in 5 min and keep for 15 min is better to maintain the digestion. By optimizing elemental analysis line, ICP measurement parameters and matrix matching and synchronization of background correction method, the high tungsten matrix effects and spectral interference are eliminated; ensure the detection performance of the method. Background equivalent concentration of 5μg/L (Nb) ~ 18μg/L (Fe), elements of the detection limit of 4μg/L (Nb) ~ 13μg/L (Fe), which used for the determination of impurities in the alloy or elements with the results is RSD <3%, recovery 97.0% ~ 103.5% corresponding with the national standard examination method.