Objective The interaction between laser and metal materials under high-speed airflow is an important aspect of laser irradiation effects. In high-speed airflow environment, laser ablation behavior characterized by high temperature rise rate can oxidize and rapidly transform the surface of metal steel, resulting in significant changes in surface heat transfer, oxidation heat release, and aerodynamic forces, which in turn affect its thermal performance and usability. The ablation behavior of metal steel is influenced by various factors such as surface high-temperature oxidation reaction, airflow convection heat dissipation, airflow erosion, and absorption rate. Currently, there are few numerical models that consider the coupling effect of these factors. Therefore, it is necessary to establish a suitable numerical model to describe the laser thermochemical ablation behavior of metal steel under airflow conditions, in order to characterize the multi physics field response law of metal steel during laser loading and improve the calculation accuracy of the numerical model.

Methods Combining experimental and simulation methods, the laser thermochemical ablation behavior of metal steel is studied. The thermal response temperature and ablation morphology of 30CrMnSiA steel are obtained through laser airflow combined loading experiments using a chemical laser (Fig.2) and a movable wind tunnel (Fig.6-Fig.7). The finite element software flow field analysis and thermal analysis module are used to numerically simulate the thermal fluid solid coupling process of laser irradiated 30CrMnSiA steel. Nonlinear changes in parameters such as reflectivity, chemical reaction heat, and latent heat of phase transformation during the ablation process are implemented using a secondary development program. The degradation process of the ablation interface in the fluid and solid domains is achieved using the dynamic grid method (Fig.4).

Result and Discussion  A numerical model for laser ablation of metal steel was established, which considers the effects of high-speed airflow, changes in reflectivity caused by thermochemical reactions (Fig.9), and heat absorption/release. For the thermochemical ablation behavior of metal steel, a chemical laser loading experiment was designed to obtain the morphology of metal melting and thermal response temperature. This numerical model can accurately reflect variables such as thermal response temperature and ablation amount during laser ablation of 30CrMnSiA steel. By simulating the dynamic changes of metal surface melting pits and the growth process of surface oxide films, this model can provide data support for the study of laser ablation effects on metals. Based on this model, the influence of strong coupling between high-speed airflow and thermochemical reactions on laser ablation was elucidated (Fig.10-Fig.11).

Conclusion A numerical model of laser thermochemical ablation of 30CrMnSiA steel is constructed based on the compressible unsteady N-S equation, the principle of high-temperature oxidation of metallic iron, and the thermal fluid solid coupling calculation method. The dynamic changes of the surface melt pit and the growth process of the surface oxide film of the metal steel under the action of airflow are simulated. By designing laser ablation experiments of 30CrMnSiA steel under airflow conditions, the thermal response temperature and ablation morphology during the ablation process are obtained, and the accuracy of the numerical model calculation is compared and verified. By combining the nonlinear changes in reflectivity and heat absorption/release caused by high-speed airflow and thermochemical reactions, the influence of airflow velocity and ablation temperature on metal oxidation heat is analyzed. The research results reveal the interaction and influence laws of multiple factors, which can provide theoretical guidance for the practical application of laser ablation.