Influence of complex geometries on the properties of laser-hardened surfaces

Abstract

Laser surface hardening provides for many advantages in terms of flexible production due to very localized and controlled energy input into the material. Laser processing offers the possibility to treat surfaces in order to locally strengthen the areas that are prone to fatigue cracking. It is well known that laser energy absorption depends on many parameters, e.g., the surface structure and the surface orientation. The incident angle of the laser beam plays a key role in this regard. When complex geometries like crankshaft fillets are treated, the surface cannot be considered a series of flat surfaces. Obviously, this leads to locally varying degrees of energy absorption. In the present work, curved surface structures were chosen in order to analyze the impact of the geometrical characteristics on surface and subsurface material properties after laser treatment. Microstructure evolution generally was found to be similar for flat and curved geometries. However, even if higher absorption in the groove due to the illumination at larger incident angles was expected, the outer parts of the curved geometry were not fully hardened. Thus, the increased effective length of the complex geometry-treated and the larger heat-affected volume are expected to have a more dominant influence on the final appearance of the subsurface microstructure. Eventually, for austenitization of the complete illuminated surface volume, the energy density needs to be increased.

Process Signature for Laser Hardening

“…In addition, models by extracting the punctual and geometrical attributes from the measured hardness profile are built to predict the shape of the hardness profile depending on the laser parameter for controlling laser hardening quality [14]. Furthermore, for the effect of surface topography on the laser energy coupling, Volpp et al [15] investigated the laser hardening of flat and curved surface and the corresponding hardening qualities. Nevertheless, no significant impact of the surface shape on the microstructures could be identified.…”

Simulation and experimental study of GGG70L laser quenching

“…Volpp et al [13] studied the influence of complex geometry on laser surface hardening, and the study showed that complex geometry does not affect the microstructure evolution process. Zhan et al [14] combined laser quenching and shot peening to double-treat QT-700-2 ductile cast iron. The results show that after the double-treating of laser quenching and shot peening, the average residual stress and hardness are improved, and the uniformity is also significantly improved.…”