Microstructural and fracture toughness characterisation of a high-strength FeCrMoVC alloy manufactured by rapid solidification

A newly-developed high-speed steel manufactured using a rapid solidification technique was investigated. Microstructural observations were conducted with the aim of comprehensively characterising the material. Furthermore, fracture toughness tests were carried out to determine the linear-elastic plane-strain fracture toughness KIc at both room temperature (20 °C) and −40 °C. A fatigue precracking method was developed to provide stable crack propagation from a manufactured chevron-notch at a ratio of minimum to maximum stress of R = −1. The results of the fracture toughness tests demonstrated that, in comparison to other tool steels, the material exhibits relatively high fracture toughness values. Furthermore, the lower shelf of KIc is already reached at room temperature. Fracture toughness is considered to be a matrix property due to the high matrix hardness. An analysis of the influence of notch tip radius ρ on notch fracture toughness KA revealed a linear correlation between the square root of the notch tip radius and KA. Upon examination of the influence of notch tip radius on fracture toughness measurements, the assumption was made that the critical notch tip radius is approximately 90 μm.

► Fatigue precracking of high-strength tool steels is possible by using an 8-point-bending device.
► Fatigue crack propagation of the newly developed tool steel alloy is mainly determined by the matrix.
► The lower shelf of fracture toughness is already reached at room temperature.
► Notch fracture toughness measurements revealed a critical notch tip radius of 90 μm.