Dynamic control of laser beam shape for heat treatment

Abstract

One of the major challenges for laser hardening is dealing with the geometrical singularities of the treated components. The problem arises from the laser hardening of uneven surfaces such as those with sharp edges or holes. In these cases, due to the differences in the surrounding volume of the material, overheating problems often appear leading to unacceptable treatment results. Despite several works tackling the problem of achieving uniform transformation profiles, the problem of the design and control of a beam delivery strategy leading to a desired transformation profile in the general case is considered to remain a true technical challenge. The main goal of this work is to present the control software developed by Talens Systems, which allows a customized laser beam delivery, providing different energy density patterns. By modifying these patterns in real time by means of scanning optics, the beam shape is able to adapt to almost any part geometry with full control of energy density, avoiding undesirable overheating effects. In addition, thanks to the modulation of the laser power and the changing speed of the scanning mirrors, the ability to “dodge” certain areas is possible and presents itself as one of the most interesting skills from the dynamic optical system shown in the present work. As an example of the success of this technology, automotive pieces have already been satisfactorily heat treated, meeting specific depth and hardness requirements. The developed knowledge and methodology could find applications in other laser processes such as cladding, welding, remelting, and alloying.

Comparative study of laser surface hardening of 50CrMo4 steel using continuous-wave laser and pulsed lasers with ms, ns, ps and fs pulse duration

“…This can be beneficial in treating intricate parts with complex geometries. Although laser beam shaping of cw laser beam has been shown viable for surface hardening of complex parts [17], pulsed lasers provide higher flexibility than cw lasers due to additional controlling parameters like pulse duration and frequency. In addition, use of pulsed lasers omits the need for expensive optical systems required for beam shaping and eliminates any energy loss associated with it.…”

Comparison of Effects of Laser, Ultrasonic, and Combined Laser-Ultrasonic Hardening Treatments on Surface Properties of AISI 1045 Steel Parts

“…For instance, the plasma surface hardening method can be applied to treat large-scale components, while the electron beam surface hardening method is used for surface modification of small-sized metallic components. However, recently advanced laser hardening systems using a diode laser [4], fiber laser [5], and disk laser [6] can significantly improve the productivity and efficiency of the laser heat treatment (LHT), both small-sized and large-scale carbon steel parts. At the same time, the application of the high-tech 2D scanning optics [7,8] and 3D scanning optics [6,9] result in an increase in the laser spot size of more than 50 mm.…”

An Optimal Genetic Algorithm for Fatigue Life Control of Medium Carbon Steel in Laser Hardening Process

“…In fact, alternating heating and cooling phases very quickly on the surface can transform it into martensite, which is harder than the bulk material [8,9]. Moreover, with a laser, the heat input can be controlled very precisely and selectively on the surface of the components, due to the ability to accurately define the illuminated area, together with the short timescale of energy transfer into the material [10]. This ensures a reduced and localized deformation of the part, therefore limiting, and eliminating in the best case, any further post-processing operation [10,11].…”

“…Moreover, with a laser, the heat input can be controlled very precisely and selectively on the surface of the components, due to the ability to accurately define the illuminated area, together with the short timescale of energy transfer into the material [10]. This ensures a reduced and localized deformation of the part, therefore limiting, and eliminating in the best case, any further post-processing operation [10,11]. However, it must be noted that there are two main sources of residual stresses during the heat treatments of steels: (i) stresses caused by the transformation of the austenite; (ii) thermal stresses caused by the different cooling rates and strain incompatibilities [12].…”