Microstructural Effects on Fatigue Behaviour of a Forged Medium Carbon Microalloyed Steel

Abstract

The effect of different microstructures on the fatigue behaviour of a medium carbon vanadium microalloyed steel has been studied. Specimens were subjected to a controlled closed die forging followed by cooling in sand, air or oil, respectively. The hardness and fatigue properties of the microalloyed steel are determined and compared with those of ferrite-pearlite and martensite microstructures obtained by cooling with different mediums after forging. Relatively fine ferrite and pearlite increase the fatigue strength of the steel, while the martensite structure reduces the fatigue strength. Characteristics of fatigue fracture surface morphology are summarized and related to fatigue crack initiation and propagation mechanisms in the forged medium carbon microalloyed steel. The cooling rate has a remarkable effect on the microstructure, hardness, and fatigue behaviour at room temperature.

Microstructural effects on high-cycle fatigue properties of microalloyed medium carbon steel 38MnVS

“…However, most of these studies were focused on the effects of forging conditions on the microstructure and mechanical properties of MA steels [6][7][8]10,[22][23][24][25], only a few focused on the effects on fatigue properties [14,15,17,20,21]. For example, Gündüz et al studied the effect of different microstructures, which were obtained through post-forging controlled cooling, on the fatigue behavior of MA steel 38MnVS6 and showed that cooling rate had a remarkable effect on the microstructure, hardness and fatigue behavior [20]. Sankaran et al developed a multiphase microstructure in a V-bearing medium-carbon MA steel using a two-step cooling and annealing treatment following finish forging in an attempt to improve fatigue resistance [14,15,17].…”

“…The forging parameters such as preheating temperature, soaking time, start and finish forging temperatures, strain (or degree of upset) utilized and the post-forging cooling rate as well as compositions of MA steel could highly influence on the microstructure and therefore play an important role on its final mechanical properties [6][7][8]10,14,15,17,20,[22][23][24][25]. However, most of these studies were focused on the effects of forging conditions on the microstructure and mechanical properties of MA steels [6][7][8]10,[22][23][24][25], only a few focused on the effects on fatigue properties [14,15,17,20,21].…”

“…Therefore, special attention should also be given to the fatigue properties of MA steels for a proper selection or replacement of materials [2,[11][12][13][14][15][16][17][18][19][20][21]. Moreover, lighter cars are in great demand for the purpose of increasing energy efficiency and reducing exhaust.…”

High cycle fatigue behavior of V-microalloyed medium carbon steels: A comparison between bainitic and ferritic-pearlitic microstructures

“…In recent years, the need for vehicles' weight reduction leads increasing demands for increasing strength, especially for increasing fatigue strength, of MA medium carbon steels. Therefore, increasing attentions have also been paid to fatigue fracture behavior of MA medium carbon steels for a proper selection or replacement of materials besides strength and toughness [2,[13][14][15][16][17][18][19][20]. Moreover, many actual forged components contain inevitable geometrical slight discontinuities or generally term of notches, which could generate local stress and strain concentrations in the notch area when are loaded.…”

Influence of the local degree of deformation on the temperature dependent fatigue behaviour of a ferritic–pearlitic steel

“…A higher cooling rate leads to a finer microstructure and, therefore, to a higher strength. 7,8 Hajisafari et al 6 report on an optimum cooling rate of 3.8 K/s for effective precipitation hardening. At either lower cooling rate or higher cooling rate, the strength of the steel decreases.…”