Effects of laser process parameters on the hardness profile of AISI 4340 cylindrical samples: statistical and experimental analyses

Abstract

In the present paper, continuous Nd:YAG laser hardening of cylindrical AISI 4340 steel specimens was studied using experimental and statistical analyses. Three Laser parameters namely laser power, laser feed speed, and sample rotation speed were selected to evaluate their in uence on the depth of the hardened zone, and the maximum surface hardness. Mathematical models were developed as a function of these three parameters and the analysis of variance (ANOVA) was used to conduct the statistical study. Microhardness measurements revealed three distinct regions in the heat-affected zone (HAZ) of all samples. The hardened zone (Z 1 ) near the surface with the highest value of hardness, the hardness loss zone (Z 2 ) where hardness started to decrease, and the overheated zone (Z 3 ) adjacent to the core with hardness values that were less than the base metal. Based on experimental measurements, a maximum surface hardness of 60.8 HRC was attained. Furthermore, the maximum depth of the hardened zone was observed as 500 µm. The microstructures of laserhardened samples were studied using optical and scanning electron (SEM) microscopies. The hardened region seemed to have hard martensitic microstructure. By comparing the predicted and measured data for maximum microhardness values it was revealed that the models represent the experimental values with correlations close to 100%.

Exploring the Effects of Laser Surface Modification on AISI 301LN Steel: A Micro-Mechanical Study

“…Moreover, the geometric dimensions of the modified layer were greater than those created with solid-state lasers. The impact of surface texture was investigated by subjecting low-carbon steel to neodymium-doped yttrium aluminum garnet (Nd: YAG) and CO 2 laser beam irradiation within the energy range of 200 to 600 mJ [14]. The findings revealed that the extent of the affected zone is primarily governed by laser power and scanning speed, resulting in the creation of a superficial layer characterized by a uniform material thickness of approximately 2 mm.…”