Grain growth and hardening in Austenite

Grain growth and hardening in Austenite Abstract: Grain growth during heat treatment has a negative effect on mechanical properties, a large grain size can result in a lower strength and susceptibility to brittle failure. In order to control the prior Austenite grain size, the effect of austentizing temperatures and holding times on the grain size and hardness in 4140 steel was experimentally investigated. Samples were heat treated to 900¡æ, 1000¡æ and 1100¡æ, and held for 1, 4, and 9 hours. After austenitizing, samples were cooled in the furnace to 850¡æ before they were quenched in water at room temperature. Each sample was cut, mounted, ground and polished. Rockwell hardness and micro-hardness tests were performed on each sample. 2% Nital etch was utilized for metallographic analysis. A Picric etch was used for grain size analysis. E112 Standard Test Methods for Determining Average Grain Size was followed to measure the grain size.