Numerical/experimental analysis of the laser surface hardening with overlapped tracks to design the configuration of the process for Cr-Mo steels

• A temperature/oxidation model has been used in the surface laser hardening with overlapped tracks for the first time.
• An innovative approach has been proposed based on design the process to meet a set of industrial realistic requirements.
• A geometrical characterization of the heat-affected zone has been developed to understand the physical background.
• Kinetic relations have been used to predict hardness and transformation maps, which have been empirically contrasted.
• Quantitative and qualitative criteria have been justified to establish a procedure to design an overlapping process.

Laser surface hardening is a promising technology to improve wear and fatigue properties of steel surfaces. When the dimensions of the surface to be treated are larger than the cross section of the laser beam several overlapped tracks are needed, and the distance between consecutive tracks becomes a fundamental design parameter. This work aims to optimize that parameter with the purpose of fulfilling a set of initial requirements for the process. A laser hardening temperatures/oxidation coupled model available in the literature is applied for the first time to the case of an overlapping process, extending its capabilities to take into account the tempering of the second track over the martensite of the first one. This model in conjunction with a convenient geometrical characterization of the heat affected zone enables a design strategy to be implemented which, using metallurgical and hardness maps, has the capability of attending different criteria. All the conditions proposed in the design of a suitable overlapping distance have been reproduced empirically for the case of the 42CrMo4 steel, and a comparison of hardness has been carried out, showing a good degree of agreement.

Figure optionsDownload as PowerPoint slide