An experimental study on the influence of porosity on hardenability

The ability to predict the hardenability is a key tool used in designing high performance steel alloys. Classically this is easily computed within reasonable error using a projected ideal diameter. PM and wrought steel specimens can be chemically identical, yet differ in properties due to porosity, and microstructural homogeneity. Using a proven method for wrought steels to predict the final properties of a designed PM alloy is therefore problematic. In an effort to apply Grossmann's predictions of hardenability for PM steel, a direct experimental investigation linking the density to hardenability was launched on prealloyed FL-4605 and FL-4605+2%Cu. As PM density decreases, sites for heterogeneous nucleation increase, and thermal conductivity decreases, which are constraints to the formation of martensite. The porosity and the microstructural deviations must be incorporated in the computation of the severity of quench, and projected ideal diameter to provide more accurate results for PM steel.