Holding time effect of pack carburizing on fatigue characteristic of v-notch shaft steel specimens

Abstract

The objective of this research is to study the effect of the holding times of pack carburizing process on fatigue characteristic of v-notch shaft steel specimens. The carbon source was taken from charcoal of unused mahogany. The holding times were 2, 3 and 4 hours. The fatigue tests were conducted on rotary bending machine. The specimens were made of low carbon steel of 0.17% carbon content. Pack carburizing was conducted to the specimens at 930°C. V-notch was made to present the stress concentration on the specimens. To see the effects of the carburizing in changing the material properties, the micro-structures and hardness tests along the cross sectional area of the specimens were carried out. The results showed that the holding time of the carburizing process influences the fatigue strength of the material. The longer the holding time will be the higher the fatigue strength. The increase of the fatigue strength is due to the carbon content on the surface. It was confirmed by the micro-structures and the hardness tests results. The cross sectional area of carburized material is divided into two zones i.e. surface zone and core zone. The surface zone consists of hypereutectoid, eutectoid, and hypo eutectoid sub-zone. The core zone is the same as raw material. The longer the holding time will be the deeper the surface zone.