Experimental Study on Electro-Spark Additive/Subtractive Repair for Worn Cemented Carbide

Abstract

Worn cemented carbide tool bits are often discarded because of the difficulty of their repair, resulting in a great deal of waste. Surface strengthening technology often extends the service life of worn tools. Electro-spark deposition (ESD) coating and matrix materials are metallurgically and closely bonded, and the approach has the characteristics of small heat input, a small heat-affected zone, and low repair cost, so it is suitable for strengthening the surface of cemented carbide tools. As the surface of cemented carbide tools is often not flat, which affects the uniformity of the deposited layer, the surface needs to be polished before ESD. Therefore, this paper proposed a method involving the electro-spark additive and subtractive repair of worn cemented carbide. Experiments involving the ultrasonic-assisted EDM grinding (UEDG) of cemented carbide were carried out. The effect of brass, 45 steel, and tungsten electrode materials on the removal rate, tool wear, and surface roughness were investigated. The results showed that the material removal rate of the tungsten electrode could reach 3.27 mm3/min, while the electrode loss was only 8.16%, and the average surface roughness was only 2.465 μm, which was better than the other two electrodes. Thus, the tungsten electrode exhibited a high material removal rate, low electrode loss, and good surface quality. The effects of the TiC, TiN, and TC4 electrodes on cemented carbide ESD were studied using optical 3D surface topography and other instruments, and the surface roughness, thickness, and hardness of the deposited layer were compared. The results showed that the surface roughness of the TC4 material reached 52.726 μm, which was better than that of the TiN and TiC materials. The thickness of the TiC deposition layer was 172.409 μm and the hardness value was 2231.9 HV; thus, the thickness and hardness of the TiC material’s sedimentary layer were better than those of the TiN and TC4 materials.

Keywords

• cemented carbide
• additive and subtractive repair
• ultrasonic-assisted electrical discharge machining grinding (UEDG)
• electro-spark deposition (ESD)