Abstract
In this work are discussed some experimental data about the obtaining of recast layers on the surface of high speed tool steel after electrical discharge treatment in electrolyte. The electrical discharge treatment of steel surface in electrolyte produces a recast layer with specific combination of structure characteristics in result of nonequilibrium phase transformations. The modification goes by a high energy thermal process in electrical discharges on a very small area on the metallic surface involving melting, alloying and high speed cooling in the electrolyte. Obtained recast layers have a different structure in comparison with the metal matrix and are with higher hardness, wear- and corrosion resistance.
Highlights
The recast layers on metals and alloys are mainly created by treating the surface with high energy stream such as laser, ion beam or electrical discharge for a very short time and pulse characteristics
The heat generated by the adsorption of the laser light provides a local melting and after controlled cooling is obtained a recast layer on the metal surface with high hardness, wear resistance and corrosion resistance
The electric discharges generate an enormous amount of heat, causing local melting on the workpiece surface and thereupon it is rapidly quenched from the liquid state by the electrolyte
Summary
The recast layers on metals and alloys are mainly created by treating the surface with high energy stream such as laser, ion beam or electrical discharge for a very short time and pulse characteristics. The electrical discharge machining uses electrical discharges to remove material from the workpiece, with each spark producing temperature of about 8000-20000 oC This causes melting and vaporizing of small volumes of the metal surface and after cooling in the dielectric fluid the melted zones are transformed in recast layer with specific structure. The EDM modified surface consists from two distinctive zones [4,5,6]: ● Recast layer ● Heat affected zone The recast layer is named white layer and it crystallizes from the liquid metal cooled at high rate in the dielectric fluid The depth of this top melted zone depends on the pulse energy and duration. There are developed on technology level processes for plasma-electrolysis oxidation and plasma-electrolysis deposition [7]
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