Electric discharge alloying of titanium and aluminium on AISI P20 mold steel

Abstract

This paper reports the enhancement of surface hardness, corrosion and wear resistance of AISI P20 mold steel by successful and uniform deposition of titanium (Ti) and aluminium (Al) using electrical discharge-based alloying. For this purpose, powder metallurgy-based green compact tool electrodes of 50–50% of Ti and Al composition were developed, and extensive studies have been undergone to study the influence of discharge current and pulse on-time on the alloyed layer thickness. A composite layer of 70 μm thickness was successfully alloyed. The alloyed regions were characterized by using an optical microscope and Field Emission Scanning Electron Microscope (FESEM). Energy Dispersive X-ray spectrum (EDS) analysis was performed to study the phenomenon of surface alloying by analyzing the elemental transfer over the work samples. One of the significant findings is that the Ti and Al elements from the tool material, and the carbon disintegrated from the hydrocarbon oil successfully migrated on the work sample surfaces. Formations of the iron carbide (Fe3C) and titanium aluminide (TiAl) were confirmed by XRD results. The alloyed region showed an increase in the microhardness by four times to that of the parent material, i.e. 300 HV0.3 to 1125 HV0.3. The wear and corrosion resistance of the alloyed region was improved. After the wear test, the mass loss in the alloyed samples was significantly reduced by 54%, whilst the corrosion resistance was enhanced by 47%.