Comparison of High Cycle Fatigue in 4340 and 300M Steel Welded with Fiber Laser

Abstract

The AISI/SAE 4340 steel and 300M have been used in severe conditions where high strength and toughness are necessary. Since there is a particular interest in the aerospace industry, they are being used in aircraft landing gear, rocket engines vessels and satellite launch vehicles. Therefore, the understanding of the weldability of these steels has been the subject of special interest. This study aims to evaluate and compare the microstructure and mechanical strength by tensile and fatigue in steel sheets of 4340 and 300M steels after laser welding and tempering heat treatments. The results showed that the welds had high hardness and small heat affected zones. Nevertheless, there was not a decrease in the uniaxial tensile properties for the 300M and 4340 steels. The decrease in fatigue life due to the welding process, compared to the unwelded condition, was small, indicating that the parameters welding were adequate and that this process is viable.