Preparing nano structural WC-Co powders by utilizing soluble raw materials by spray drying and synthesis method

Thermal sprayed carbide such as WC-Co(Cr) and Cr3C2-NiCr coatings are well known and widely used for wear protection purposes. Submicron, nano-sized and multimodal carbides in cermets have shown promising results in gaining hardness and wear performance. Presented study is a part of the research aiming to create a novel powder manufacturing route for homogenous nano structural WC-Co(Cr) powder for thermal spraying by utilizing water soluble raw materials. One major challenge for this manufacturing route is to produce dense and spherical powder structure by spray drying method which during synthesis stage will conserve shape even if desired phase structure will form. In this study powders were manufactured via spray drying method from water based solution with raw materials ammonium meta tungstate (AMT) as a tungsten source, glycine as a carbon source and cobalt acetate as a cobalt source. Before the spray drying stage additives were added to experimental solutions to modify solution properties. Solutions were characterised by rheometer and in addition pH-value was measured. Also the effects of spray drying parameters to powder form and particle size was analysed. After spray drying powders were heat treated in Ar atmosphere. The morphology and internal structure of powder particle size was analysed with scanning electron microscopy (SEM) both after spray drying and heat treatment stage and an X-ray diffractometer (XRD) was used for phase structure analysis. With modifications on solution by additives and on spray drying parameters powder particle size, shape and density could be improved but still particle shape was not conserved during the heat treatment stage.