Electro-spark Process Research Articles

Remanufacture of Die Casting Dies

Die casting dies are essential parts for die casting engineered metal products and usually fail due to a variety of reasons. The objective of this paper is to investigate the potential benefits and possibility of remanufacturing die casting dies. Firstly, with respect to the entire life cycle, a technical framework for die remanufacture is presented. And then based on the failure modes of die casting dies, life extending technologies covering the whole life cycle are reviewed according to the different stages: Pre-failure stage and Post-failure stage. While measurements within the Pre-failure stage are shortly and briefly surveyed, extensive effort is made to survey the recondition technologies-welding technologies which could be the only measure to put worn/failed dies into operation. The most commonly utilized welding technologies are Tungsten Inert Gas (TIG) Welding, Plasma Arc Welding (PAW) and Laser Beam Welding (LBW), and other types of welding techniques including Electro Spark Process and Cold Spray are also applied for repairing die casting dies. Lastly, research gaps and industrial challenges indicate that more research attention is required to finally commercialize the remanufacture of die casting dies.

The properties of nanocomposite coatings formed on a steel 20H surface by means of electrospark processing using rod-shaped electrodes of steels 65 G and Sv 08

The phase composition, the sizes of the grains (crystallites), the microstructure and microhardness, and the physical and mechanical properties of the nanocomposite coatings on the 20H steel surface resulting from the electrical processing in a gas medium by compact electrodes made of steels 65G and Sv08 with regard to the processing velocity and their influence on the wear resistance of the composition have been investigated.

Control of the discharge plasma effective volume at the contact electrospark process in liquid

New experimental results that allow executing stabilized critical discharges between metallic granules in a liquid by a combination of electrotechnical parameters of the discharge contour are obtained. The form of the channel and the law of its extension, taking into consideration the momentary electrical power, were determined. This has allowed offering dependences for the regulation of an affective volume of discharged plasma. The influence of different-diameter gas inclusions on the processes of formation and development of the discharge was estimated.

NiCr Alloy Coating Deposited on the Surface of 35CrMo Steel by the Electrospark Process

Strengthened coating on the surface of 35CrMo steel alloy was deposited by electrospark process using NiCr electrode. The bond strength and microhardness of the coating was checked and the microstructure of the strengthened coating was analyzed using the optical micro-scope, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion spectrum (EDS). The results show that the bond strength between the coating and the base metal is 495.1MPa, and the hardness of the coating surface is about 2 times than that of the base metal, and the property of the workpieces surface has become better. The coating is a metallurgical reacting bonding layer between the base metal and the NiCr electrode, and its main ingredients are FeNi and NiCrFe.

Microstructures and wear properties of TiN-based cermet coating deposited on 1Cr18Ni9Ti stainless steel by electrospark process

A simple and effective surface treatment technique, electrospark deposition (ESD), has been successfully applied to deposit TiN-based cermet coating on stainless steel substrate. The nitrided coating had an average thickness of about 30 μm and formed metallurgical bonding with the substrate. The microstructure of the coating was mainly composed of TiN phase and ferrite (α-FeCr) phase. Its microhardness reached 889HV. The experimental results demonstrated that the nitrided coating had an excellent sliding wear resistance because the hard TiN phase distributed in the coating increased the resistance to micro-cutting and plowing during the sliding wear test, which effectively improves the surface performance of stainless steel substrate.

Cr 7C 3-based cermet coating deposited on stainless steel by electrospark process: structural characteristics and corrosion behavior

The electrospark deposition (ESD) technique has been successfully applied to deposit at room temperature a cermet layer of Cr 7C 3 carbide bound with 20 wt.% Cr on a AISI 304 stainless steel substrate. It has been possible to obtain a fully dense, uniform and strong adherent coating layer of 10–30-μm thickness. The corrosion properties of this coating system have been evaluated in HCl electrolyte by conventional anodic polarization tests and impedance measurements. The results indicate an exceptional resistance of the coating to both general and localized corrosion attack. Some surface stress relief microcracks formed during the ESD deposit cycles do not impair the corrosion resistance of the coating even after long time immersion in HCl.

Selecting the optimum electroerosion treatment conditions for chromium carbide materials

1. During the electrospark processing of cermets based on chromium carbide, the surface layer is impoverished with respect to the more fusible metallic bond. The degree of such impoverishment is determined by the process cycle and the composition of the interelectrode medium. 2. With certain process cycles (Imean ≥ 5 A for generator VG-3V and Imean ≥ 3 A for generator MGI-2) the surface layer develops microcracks which reduce the strength of the material being processed. 3. For electroerosion defect-less processing of material based on chromium carbide it is desirable to use short impulses and low energy values. It is possible to recommend a lamp generator of the type GIT-1m, GIT-2 (or the similar GIL, VChIU, VGI) for the energy sources needed to process the cermet under review, with impulse energies of not more than 0.04 J, and also generator VG-3V with a current of up to 2 A. Vibrating or rotating one of the electrodes pumping liquid through the electrode gap is essential. 4. It is desirable when processing cermets with generators of the type GIT to use industrial water as the interelectrode medium; this substantially improves the quality of the surface layer with a slight reduction in process rate.