DOES LIQUID-NITROGEN IMMERSION IMPROVE WEAR-RESISTANCE OF STEEL AND CAST-IRON

Liquid nitrogen immersion, sometimes known as cryogenic treatment, is useful for ensuring dimensional stability in precision components or for increasing the depth of hardening in steels. Its use for increasing the wear resistance of steels and cast irons is more controversial. Paper mill engineers have expressed interest in the method for improving the abrasion resistance of items such as refiner plates, slitters, and calender rolls. The Pulp and Paper Research Institute of Canada investigated the technique, using a range of steels and cast irons typically found in pulp and paper mills. Of eight alloys tested, only a tool steel showed significant increase in wear resistance after immersion. The performance of two steels decreased, and the remaining alloys showed no change in behavior. The hardness of alloys after liquid nitrogen treatment was not an indicator of subsequent wear performance. Immersion had little effect on improving the wear resistance of the irons and steels, the study indicated. Improvement in the best case was less than 10%, and in some cases immersion actually reduced alloy abrasion resistance.