Surface hardening effect on the fatigue behavior of isotropic beam

Abstract

an experimental study of the impact of surface hardening on the high-cycle fatigue behavior of an isotropic beam.The beams are made from low carbon steel.The experimental work included mechanical tests, surface heat treatment, fatigue tests, and microscopic inspections.The surface hardening was done by using a pack-carburizing process at atemperature of 925 C holding time variation(2, 4, and 6 hoursfollowed by quenching and tempering process and using the carbonitriding process at a temperature of800 °C and for periods(0.5, 1 and 1.5hour)then quenching directly inwater.an experimental fatigue test indicates that various behaviors depend on surface heat treatment and time soaking.that carbonitriding has a greater impact on fatigue strength and life than the specimen has been treated with pack carburizing.the time soaking increase,the fatigue life will increase for both types of surface heat treatments.the specimens that were hardened using the carbonitriding process achieved a higher surface hardness as the hardness increased to1571.94 HV,while the untreated specimens were293 HV.Compared with the hardening using the pack carburizing process.The cross-sectional area of the treated steel with pack carburizing and carbonitriding is divided into two-part, that is Surface layer and core.The surface layer consists(of carbon, carbon, and nitrogen).The longer the retention time, the deeper the surface layer.

Keywords

• fatigue behavior
• s-n curve
• carbonitriding
• pack carburizing