Fatigue crack propagation in nine steels, type SAE 43XX, from 0.20 to 1.00 % C, for the simulation of the fatigue behavior in a carburized layer of the SAE 4320

Abstract

The objective of this paper is to evaluate the crack propagation rate of the SAE 4320 steel carburized layer. For the simulation of a carburized layer, samples made of SAE 43XX were employed, varying the content of carbon from 0.20 to 1.00 %. Specimens were copper layer electroplated, and then, they were heat treated in a cycle of carburizing, quenching, and tempering in five different temperatures to expose them to the thermal effects without diffusion of carbon. The results of the microhardness for the steels and for the analyzed conditions are presented in this work. The curve of microhardness has the same profile of a carburized layer for the SAE 4320 heat treated in the same conditions. The crack growth rates as a function of delta K for three tempering temperatures are plotted and the curves are shown. These results show that when the hardness is high (at 200 ºC tempering temperature), there is a scattering of the curves and for the case of lower hardness (at 600 ºC tempering temperature), the curves are closer. With increasing of tempering temperature there is a decreasing of the hardness and a significant effect of the metallurgical condition of the resistance of fatigue crack growth. Furthermore, with decreasing of the carbon content there is a very significant increase on the resistance of the fatigue crack growth. As a result of that, in the case of a carburized layer there is a raise of the fatigue crack growth resistance when the crack grows into the steel, from the surface (higher hardness) to the core (lower hardness).

Influence of Carbon Content on Elevated Temperature Fatigue Properties of Different Steel Alloys

“…This observed by the decreasing in slope of the da/dN and ∆K curves and this depending on the metallurgical condition. It confirmed that the fracture toughness and da/dN -∆K slope vary at inverse proportion to the carbon content and microhardness [5].…”

“…The test temperature was 600ºC and the stress ratio R=-1. It was found that the fatigue life at different stresses for the three methods is given in table [5]. The increase of carbon content from 0.02%C to 0.032%C causes an increase in the fatigue life at high temperature and then the life reduced at 0.041%C content for 300, 400 and 500 MPa applied stress [13].…”

The Influence of Repeated Heat Treatments on The Propagation of Fatigue Cracking of Medium Carburized Steel

“…The rolling contact stress shows that the subsurface fragment life begins to increase as the adhesive austenite increases. The crack propagation rate of the carbon steel layer was evaluated according to SAE 4320, and it was found that as the carbon content decreased, the resistance to stress crack growth increased [15]. In [16], they used finite element modeling to find the influence of carbon allocation on residual stress in gears, then proposed a method to design the minimum case depth to obtain the lowest residual stresses.…”

Effect of Hot Rolling on Microstructural Evolution and Wear Behaviors of G20CrNi2MoA Bearing Steel

“…Bearings are an important part of high-speed railway trains, and thus, their quality and stability receive considerable attention [1,2]. The fatigue performance and damage evaluation of the high-speed railway bearing steel are also taken seriously [3,4]. To bear the thermal-mechanical load during operation, the service performance requirements of high-speed railway bearings are mainly focused on two characteristics: high wear resistance of the surface and high impact toughness of the core.…”