Deep cryogenic treatment of T15M powder metallurgy high speed steel

SLX-80 cryogenic treatment system was used for deep cryogenic treatment of T15M powder metallurgy high speed steel.Room temperature magnetic and thermo-magnetic properties of the samples were examined by vibrating sample magnetometer of a physics property measurement system(PPMS-VSM).The results show that in the holding and cooling stages during tempering at 843 K for 1 h,retained austenite in the steel is transformed to martensite.In the deep cryogenic treatment in the range of 300-10 K,magnetization of the steel decreases during cooling in the range of 110-10 K due to carbide precipitation from martensite,and the magnetization increase during heating in the range of 40-230 K due to martensite transformation of retained austenite.Deep cryogenic treatments promote martensite transformation of retained austenite,suppress carbide precipitation from retained austenite,and especially promote fine carbide precipitation from martensite.With the deep cryogenic treatment before and after the first temper,the hardness values of the steel after the third temper can increase 2.0 HRC and 1.4 HRC,respectively.