Effects of deep cryogenic treatment on the microstructure and friction performance of M35 high-speed steel

Abstract

The tempered M35 samples were deep-cryogenically treated (DCT) at temperature - 240 C for a long time. The microstructure and hardness were characterized by SEM, and Rockwell together with Vicker's indenter respectively. The wear resistance was tested by a ball-on-disc friction and wear testing against Si3N4 balls. Comparing to high-speed steel without further treatment, the size of grains was reduced to 9.94 μm and promoted the formation of carbides after DCT. However, it was found that the hardness of the samples before and after DCT kept almost the same. Under high load, the wear resistance was slightly improved. This was probably responsible for carbides precipitation and Co precipitated from the α-Fe matrix during DCT.