Abstract: This experimental work intended to investigate the effects of cryogenic treatment on the wear behavior of D6 tool steel. For this purpose, the temperature was used -185oC as deep cryogenic temperature. The effects of cryogenic temperature (deep), cryogenic time (kept at cryogenic temperature for 36 hr) on the wear behavior of D6 tool steel were studied. The findings showed that the cryogenic treatment decreases the retained austenite and hence improves the wear resistance and hardness. Due to more homogenized carbide distribution as well as the elimination of the retained austenite, the deep cryogenic treatment demonstrated more improvement in wear resistance and hardness compared with the conventional heat-treatment. By increasing the keeping time at cryogenic temperatures, more retained austenite was transformed into martensite; thus, the wear resistance was improved and further hardness were observed. This experimental work also intended to investigate the role of multiple tempering before and after cryogenic treatment on friction and wear behaviour of D6 tool steel as classified by American Iron and Steel Institute (AISI). D6 tool steel is used for measuring tools, blanking dies, forming dies, coining dies, long punches, forming rolls, edging rolls, master tools, extrusion dies, drawing dies, moulds for pressing abrasive powders etc. The different combination of heat treatments like hardening (at 1020°C) for one hour, tempering (at 210°C) for two hours and deep cryogenic treatment (at -185°C) for 36 hours was done on D6 tool steel. Wear test were performed using pin-on-disc wear tester to which two different normal loads (3.1Kg and 5.1Kg) and two different velocities (1.5m/s and 2.5m/s) were applied. Hardness of specimens was measured by using Rockwell Hardness tester. Microstructural characterizations of the differently heat treated specimens have been done by image analyzer software with inverted microscope. The findings show that the cryogenic treatment improves the wear resistance and hardness of D6 tool steel. The results indicate that, in HCT specimens there was large reduction in the wear rate and markedly enhancement in wear resistance of the D6 tool steel.
Keywords: AISI D6 tool steel, cryogenic treatment, wear rate and wear resistance.