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Electro-Spark Deposition: Overview and Mechanism

SparkDepo is TechnoCoat's electro-spark deposition (ESD) process for coating and on-site overlay repair of machine components, molds and dies.

Coating for machine components, molds and dies life-up

The coating with WC, TiC, Cr3C2, etc. protects the surface due to its extreme wear resistance, heat resistance, scuffing resistance, and corrosion resistance.

Easy on-site overlay repair by anyone

Overlay repair for scratching, scuffing, wearing, corrosion and pinholes using Ni, Co, Cu, and Al alloys, with low heat input that avoids the distortion and cracking risks of conventional welding.

Reduced downtime

Reduces downtime for repair and the number of spare parts kept in inventory, since worn dies and molds can be repaired on-site instead of replaced.

How electro-spark deposition works

Electro-spark deposition (ESD) is a low-heat-input electrical discharge process. A rotating or vibrating electrode is brought into repeated contact with the workpiece; each spark discharge transfers a microscopic amount of the electrode material and metallurgically bonds it to the substrate surface. Because the heat-affected zone is extremely small and localized, ESD coating and overlay can be applied without the distortion, residual stress, or cracking risk associated with conventional welding or thermal spray processes.

The process is controlled through three main parameters — output capacitance, output voltage, and spark frequency — which together determine deposition speed, surface roughness, and diffusion depth. TechnoCoat's SparkDepo power units (Model 200 and Model 300) and the MicroDepo Model 150 implement this process at different power/output levels for industrial and portable use.

DeviceInputOutput capacityFrequency rangeDimensionsWeight
MicroDepo Model 150100V AC single phase (110/200/220V available)500 VA max.60–1,600 Hz255W×320D×290H mm14.7 kg
SparkDepo Model 200220V AC single phase, 50/60 Hz1.6 kVA60–2,000 Hz323W×420D×410H mm31.4 kg
SparkDepo Model 300220V AC single phase, 50/60 Hz2.0 kVA60–2,000 Hz323W×420D×410H mm31.8 kg

Principle diagram

Electro-spark deposition principle and property graph diagram

Frequently asked questions

Electro-spark deposition is a low-heat-input electrical discharge process that metallurgically bonds a coating or overlay material to a metal surface, spark by spark, using a rotating or vibrating electrode. It is used for both wear-resistant coating and on-site overlay repair of molds, dies, and machine components.

ESD uses far less heat input than conventional welding, so it does not cause the distortion, residual stress, or heat-affected-zone cracking that welding can introduce. Unlike thermal spray, the deposit is metallurgically bonded rather than mechanically bonded, giving stronger adhesion.

Coating electrodes include tungsten carbide (WC-Co), titanium carbide (TiC-Ni/TiC-Co), chromium carbide (Cr3C2-Ni), vanadium carbide, titanium boride, zirconium boride, and pure metals such as cobalt, nickel, molybdenum, titanium, tantalum, zirconium, tungsten and platinum. Overlay electrodes (SD-01, SD-11, SD-21, AL-02, CU-02) are matched to tool steels, hardened steels, aluminum alloys, or copper alloys depending on the base metal being repaired.

Three settings on the power unit — output capacitance, output voltage, and spark frequency — combine with electrode diameter and applicator type (standard, miniature, or vibrating) to control roughness, speed, and diffusion depth. Higher output/voltage settings deposit faster but rougher; lower settings and finer electrodes produce a smoother finish.

Mechanism animation videos are listed on the Videos page.

Spec sheets and comparison data are on the Downloads page.