Study of the recast layer of a surface machined by sinking electrical discharge machining using water-in-oil emulsion as dielectric

• Published in: Applied surface science 2011-05, Vol.257 (14), p.5989-5997
• Main Authors: Zhang, Yanzhen, Liu, Yonghong, Ji, Renjie, Cai, Baoping
• Format: Article
• Language: English
• Subjects: Carbides; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Dielectrics; Electric discharge machining; Electrical discharge machining (EDM); Emulsion; Emulsions; Exact sciences and technology; Kerosene; Oxides; Physics; Recast layer; Scanning electron microscopy; Surface roughness; Water hardness; Water-in-oil
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2011.01.083

► The properties of the recast layer formed in the sinking electrical discharge machining process using water-in-oil emulsion as dielectric were characterized and compared with that formed using kerosene and de-ionized water as dielectric. ► The composition and phases presented in the recast layer were identified. ► The formation of micro-crack and micro-void was discussed. ► Micro hardness of the recast layer was determined. Electrical discharge machining (EDM) caused a recast layer to form at the machined surface of the workpiece. The characteristics of the recast layer have a great relationship with the type of dielectric. The research work in this paper aims to acquire a profound knowledge of the recast layers of a surface machined by sinking EDM using water-in-oil (W/O) emulsion as dielectric. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrograph (EDS) and micro hardness analysis were performed. The characteristics of the recast layer formed in W/O emulsion were investigated by comparing them with those of the recast layer formed in kerosene and de-ionized water dielectric. It was found that the recast layer formed in W/O emulsion exhibited larger surface roughness, thickness and micro hardness compared with that formed in kerosene and de-ionized water. Both carbide and oxide were detected in the recast layer formed in W/O emulsion whereas only carbide was detected in the recast layer formed in kerosene. Due to the higher supersaturation of gases in the melted material, the recast layer formed in W/O emulsion was found to possess more micro-voids than that formed in kerosene and de-ionized water.