No abstract

The surface of tungsten carbide with Co-binder (WC-Co) after wire electro-discharge machining (W-EDM) with and without induced discolouration was investigated by XPS, AES and SEM. The measurements show that the eroded surface is at least partly covered by a layer containing Zn and Cu oxides, and also small amounts of W and Co. The Zn and Cu originate from the wire (brass wire covered with Zn) used during the W-EDM and/or from the water, which contains Zn, Cu, W and Co from W-EDM processes performed earlier on the same machine. The W and Co stem from the water or from the base material of the work piece. On the samples with induced discolouration a dark pattern is visible at the surface. Measurements on these samples show an increased amount of Co within the dark pattern.