Papers by Keyword: Laser Surface Hardening

Abstract: Advanced High-Strength Steel (AHSS) grade 980 is essential in industries demanding superior mechanical performance, such as automotive and aerospace engineering. This study investigates the laser surface hardening (LSH) process as a method to enhance surface properties, emphasizing the influence of varying laser power levels on microstructural and mechanical outcomes. Key microstructural zones, i.e. melting zone (MZ), hardening zone (HZ), and heat-affected zone (HAZ), were analyzed, and each contributes distinctively to the improved surface characteristics. The findings demonstrated significant enhancements in surface hardness, achieving peak values of 591 HV under optimized conditions. Additionally, the process enabled precise control over microstructural refinement and the depth of hardening. These results underscore LSH as an effective and adaptable technique for optimizing AHSS 980, providing enhanced wear resistance and long-term durability for high-performance applications.

Abstract: Laser surface modification technology is one of the most advanced technologies, which uses laser to modify the characteristics of the surface to offer superior performance for various industrial applications. In this study, laser surface hardening behavior of GM246 case iron was investigated. Result shows that excellent laser surface hardening of GM246 cast iron need low power density and scanning speed. With power of 2500 W, scanning speed of 300 mm/min and power density of 2500 W/cm², the laser surface hardening of GM246 cast iron achieved the hardness of 790HV, which was 2-3 times higher than the hardness of base metal. Also, the depth of laser surface hardening case achieved 0.9 mm and the hardening case demonstrated three subzones.

Abstract: In the present work, we investigate the influence of laser radiation on the evolution of microstructure and wear resistance of X38CrMoV5-1 tool steel in hardened and tempered condition. The microstructure of the laser surface hardened zone consists of fine and coarse grained carbides (M₂₃C₆, M₇C₃, MC or M₂C) which are dispersed within martensite matrix. On the other hand, the laser melted microstructure is characterized by martensite, retained austenite and fine carbides precipitated in the inter-dendritic zone. The laser surface affected zone microstructure exhibits the enhanced hardness in the range from 857 to 775 HV in comparison with quenched and tempered conditions (720-655 HV) and decreases from the surface to the soft zone with a typical hardness of 530 HV. The wear resistance of the laser treated samples is investigated by “ball on disc” method, which shows a significant improvement as compared to that in quenched and tempered condition.

Abstract: Laser surface hardening is widely used. The complexity of the surface restricts its application. To solve this problem, it is necessary to study the path of the laser spot. By comparison the difference of CNC cutting machine and laser processing machines, the control system of laser spot is built. And the method of alignment for work coordinate system is obtained. NC programming model of the laser beam is established using CAM software. The change of area of spot when laser beam projected to the different normal angles surface was analyzed, and it is get the relationship of normal angles and feed rate. The complex surface laser surface hardening is realized.

Abstract: The effect of defined preloading in the tensile and compressive regime on the near surface (residual) stress distributions, which result from laser surface hardening, is systematically studied in-situ, i.e. under the applied preload and after unloading. Samples made of steel grade AISI 4140 are defined surface hardened by means of a high-power diode laser (HPDL) system during uniaxial compressive elastic loading at-300 MPa as well as during uniaxial elastic tensile loading at 300 MPa using a custom designed 4-point-bending device, which can be mounted on an X-ray diffractometer. The results of X-ray stress analysis were compared to data derived for a sample state unaffected by any preload. Without external loading compressive residual stresses are induced inside the process zone that are balanced by tensile residual stresses outside this zone. The investigations show that external loading in the tensile and compressive regime has a strong impact on the resulting lateral residual stress distribution in loading direction. The results further indicate that undesirable tensile residual stresses outside the process zone can even be suppressed by using a defined appropriate preloading in the tensile regime.

Abstract: A safe and healthy work piece is important for sustainable manufacturing process. Green laser surface hardening is a heat treatment process on a part of its application does not use water or oil as quenching media, because it is self-quenching and less detrimental to the environment. Since it is an energy saving process it is fast being adopted by manufacturing industries. Quenching media used in conventional heat treatment process for a sudden cooling of the heated work piece to get hard structure transformation. Unfortunately the reactions of quenchant with hot working also have several negative health, production cost, and environmental impact.This paper focuses the experimental investigation into the roller of green surface hardening on energy saving, the production cost of the industrial components. A comparative study of surface hardening under conventional and laser sources was conducted using similar components. The results show that the quality of hardening improved in laser hardening but the process time increased marginally at one stage and reduced at other shapes of manufacturing. In analyzing the process cost laser hardening show cast saving notably.

Abstract: The effect of processing atmosphere on the microstructure and residual stresses are studied for laser surface hardening on steel samples of grade AISI 4140. Samples were hardened in air, vacuum and inert gas atmosphere (Helium) by means of a stationary laser beam. A high-power diode laser (HPDL) system was used in combination with a custom-designed process chamber. Residual stress distributions in lateral and in depth direction were analysed after laser processing by means of X-ray diffraction according to the well known sin² - method. X-ray residual stress analyses were supplemented by microscopic investigations of the local microstructure. The results indicate a widening of the compressive stressed region in lateral as well as in depth direction by surface hardening in inert gas atmosphere compared to laser surface hardening in air or vacuum atmosphere. This is due to the local heating flux distribution during the laser assisted heat treatment which is strongly affected by the processing atmosphere an leads to an extension of the hardening zone when using helium as inert gas.

Abstract: Analytical expressions for the temperature rise in a semi-infinite workpiece due to the heating with CW and repetitive laser pulse irradiation have been derived. It has been shown that the soaking time at a temperature above the phase transformation temperature, on which the homogeneity of microstructure and the depth of hardening depend, can be increased by heating with repetitive laser pulses. Experimental results of surface hardening of high-carbon steel with repetitive laser pulses showed higher depth of hardening and better microstructure homogeneity compared to those with continuous wave laser.

Abstract: At present work, the microstructure and corresponding hardness of 17-4PH stainless steel were investigated by the process of CO₂ laser surface quenching and aging treatment. The hardness of the phase transformation zone in the hardened layer was 433.2HV, higher than 378.1HV of the matrix, which was attributed to the fine-grain and solution strengthening after laser quenching. The hardness of the phase transformation zone increased further to 464.5HV after an aging treatment at 520°C due to the precipitation strengthening of fine secondary phase particles.

Abstract: Laser surface hardening is a method used for surface modification without affecting the bulk properties of materials. Due to rapid cooling and little thermal penetration in the surface layer, a homogenous structure and little distortion are usually obtained. When a high power laser irradiates a material surface, a part of the laser energy is absorbed and conducted into the interior of the material. If the absorbed energy is high enough, the material surface will melt and even vaporizes. Consequently the temperature of the process is of promote importance to incorporate an appropriate structural layer. In this regard, a study has been carried out to implement a mathematical modeling method to control the temperature gradient, which affects on the depth of the hardened layer. The model is based on solving the heat transfer equation and such a condition by assuming that the thermo-physical properties of the material are independent of the temperature. To evaluate the application of the proposed model, laser surface hardening was carried out to AISI 1050 steel, using a 1 kW CO2 laser. It was shown that the experimental results obtained are in good agreement with the proposed model.