Quench hardening of 0·4%C steel using aqueous electrolyte plasma as heat source

Quench hardening of 0·4%C steel has been achieved using aqueous electrolyte plasma as heat source. Cylindrical specimens (8 mm diameter) of 0·4%C steel (cathode) were placed at the centre of a cylindrical stainless steel ring of 100 mm diameter (anode) in 15 wt-%Na₂CO₃ aqueous solution. Continuous electrolyte plasma was generated by electrical discharge at voltages higher than ∼90 V in a narrow layer at the specimen (cathode) surface. The aqueous electrolyte plasma caused rapid heating of the active electrode (cathode) to 900–1200°C in few seconds at applied voltages in the range of 95–140 V. On subsequent rapid cooling, the steel specimen transformed to martensite structure. The process can be adopted for surface modification techniques such as nitriding and carburising. Feasibility of anodising using this technique may also be explored.