Wear and Fatigue Behaviour of Deep Cryogenically Treated H21 Tool Steel
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The influence of deep cryotreatment before and after double tempering on hardness, wear rate, surface finish and fatigue limit of AISI H21 tool steel has been examined. In the present work, H21 tool steel has been subjected to heat treatment at 1195 °C, double tempering at 540 °C, deep cryotreatment at − 185 °C and soft tempering at 100 °C. The microstructure of samples has been characterized for the number density of carbides, hardness, wear rate, surface roughness and fatigue limit. The fatigue test has been carried out using a rotating bending fatigue machine to study the fatigue strength of the material. The obtained results show that the HTTC24 specimen reduces the wear rate by ≈ 24% and surface roughness by ≈ 21% with an increase in fatigue limit by ≈ 13% compared to HTT specimens. This has been attributed to the increased number density of carbides and hardness; and approximately the complete conversion of retained austenite content into martensite.
KeywordsH21 tool steel Deep cryotreatment Carbide density Wear rate Surface roughness Fatigue limit
Dr. N.B. Dhokey, Professor, Department of Metallurgy and Materials Science, COEP, Pune-411005, India; is greatly acknowledged for valuable suggestions and providing laboratory facilities to complete the present work. Also, Dr. Tarang Shinde is gratefully thanked for providing his technical suggestions.
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