Fracture Toughness Evaluation of Powder Metallurgical ASP2030 High-Speed Steels Using Flexural Specimens and Finite Element Method

Abstract

The development of superior mechanical properties in medium-Mn requires the optimization of microstructural parameters such as retained austenite (RA) stability, volume fraction, and morphology. The present work explores the possibility of using a continuous annealing approach instead of conventional batch annealing to perform an intercritical annealing (IA) treatment in a hot-rolled strip of an Al-alloyed 5Mn steel. Dilatometric studies were performed at a temperature of 680 ºC with soaking times ranging from 1 to 300 min to follow the microstructural changes as a function of time. The microstructures thus obtained were thoroughly characterized by means of X-ray diffraction, SEM and TEM, TEM-EDS microanalysis and EBSD phase and orientation maps. It was observed that with increasing soaking times, the volume fraction of retained austenite gradually increases, albeit at the cost of its stability. The comparison of martensite start temperatures (M s ) based on the chemical composition of austenite at 680 ºC with that experimentally obtained at higher process temperature revealed the effect of the grain size on the reduction of RA stability for longer process times. Accordingly, mechanical tests results showed that the yield stress, tensile strength and hardness decrease with an increase in the IA soaking time.

Fracture Toughness of Vacuum Sintered AISI M3:2 High Speed Steels

“…They have been used for several decades as unique materials for drills, broaches, and blades. In other words, applications where the material must exhibit oxidation resistance, high heat resistance, and hardness 1,2 .…”

“…At present, there is a general acceptance that fracture toughness of high speed steels is an important property. According to studies 1,9,10 , the influence of microstructure parameters, such as grain size, fine carbides, microcavities and impurities promote failures in the material, affecting its fracture toughness.…”