Volume 6, Issue 1 (January 2009)
An Investigation on Quenching Performance of Hot Alkaline Bath
An investigation was done on understanding the cooling affect of alkaline salt bath medium on microstructure, mechanical and surface properties of AISI 1045 steel in comparison with oil. Salt bath medium used in this research contained 40 % NaOH and 60 % KOH with addition of 5 wt. % water at 205°C. H-value of the medium was determined by the Rushman Lamont method. This value was found to be 0.4. Hardening of 1045 steel in salt bath resulted in higher hardness and improved hardenability in comparison with oil quenching. Strength and ductility was also increased by this treatment. This was found to be a direct result of different microstructures evolved during quenching treatments. Hardening of 1045 steel in this medium resulted in an almost uniform microstructure which consisted of fine martensite and bainite. In comparison the microstructure of oil quenched sample was martensite, ferrite, widmanestatten ferrite and pearlite. Surface properties also improved by decrease in surface roughness and a good bearing area curve.