A comprehensive review of metal laser hardening: mechanism, process, and applications

In recent years, the industry has demanded high hardness, wear resistance, corrosion resistance, and other properties for critical components made of steel and its alloys. Enhancing the surface properties of a part by applying modification techniques to its surface is considered to be an economical and efficient method. Laser hardening, as a new surface modification technology, has received more and more attention due to its high hardening efficiency, fast cooling rate, and excellent surface properties. Laser hardening technology has good application prospects in surface modification, and significant progress has been made in the exploration of laser hardening strengthening mechanisms, optimization of process parameters, high-quality preparation of hardened layers, and theoretical simulation. However, some problems need to be addressed in the practical application of the technology. This paper reviews the research progress of the laser surface hardening process for steel and its alloys, including numerical investigation, process optimization, hardening performance analysis, and external field-assisted laser hardening technology. It also discusses the problems and challenges faced by the technology and gives an outlook on its development trend.