Abstract:A CO2 laser with a fixed laser power of 1.8 KW was employed to harden the surface of some AISI 4340 steel specimens, with a scan rate from 5 to 10 mm/s. The influence of scan rates and tempering treatments of the alloy on the hardness profile and microstructure of the laserhardened zone was analyzed. Microstructures in the hardened zone consisted of mainly lath and twinned martensites. However, depending on the scan rate, autotempered martensite has also been found. In the transition zone of laser-treated spec… Show more
“…Over the next 200 m, which represents the HAZ, the hardness values remain constant until dropping to 400 Knoop at 400 m. At the end of the heataffected zone, the hardness values climb back up to 500 Knoop in the substrate and stay around this value for the remainder of the sample. The results of microhardness testing for Lots 1, 2, and 4 were similar to those reported by Shuie and Chen [22] who studied laser transformation hardening of AISI 4340 with a CO 2 laser.…”
“…Over the next 200 m, which represents the HAZ, the hardness values remain constant until dropping to 400 Knoop at 400 m. At the end of the heataffected zone, the hardness values climb back up to 500 Knoop in the substrate and stay around this value for the remainder of the sample. The results of microhardness testing for Lots 1, 2, and 4 were similar to those reported by Shuie and Chen [22] who studied laser transformation hardening of AISI 4340 with a CO 2 laser.…”
“…Precipitation and carbide coarsening may occur even at high cooling rates experienced during laser transformation hardening [9,16,17]. This might have an effect on the hardness and properties of the quenched microstructure.…”
Section: Phase Transformations During Laser Hardeningmentioning
“…Therefore, the temperature of the surface layer during laser hardening of SKD61 steel should be higher than the austenized temperature of 1010°C in traditional quenching. Following this logic, the temperature of the surface layer should be high enough for quenching so that it will enable the complete transformation of austenite into martensite (Shiue and Chen, 1992;Bradley and Kim, 1988). Figure 10 presents the temperature distribution in the surface layer obtained by using the modified Ashby-Easterling heat-transfer equation (Eq.…”
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.