Surface hardening of a mould steel by laser quenching

The objective of this work is to study the laser quenching process of AISI P20 + S mould steel, focusing on improving surface hardness and wear resistance. AISI P20 + S steel was laser-quenched using temperatures of 1000 °C and 1200 °C, and laser beam overlap rates of 10% and 25%. The as-received and laser quenched steel was characterized by optical microscopy, scanning electron microscopy, and X-ray diffraction. After laser quenching, nanoindentation and pin-on-disk tests were performed to determine hardness profiles and assess wear resistance, respectively. The hardness at the surface more than doubled compared to the hardness of the untreated steel, confirming the formation of martensite. The 1000 °C laser quenching resulted in a depth lower than 700 μm, with a surface hardness close to 8 GPa. At 1200 °C, the depth increased to nearly 1400 μm, and the hardness reached 8-9 GPa, although the thicker oxide layer formed during the laser treatment led to an increase in the wear coefficient and volume. Due to the detachment of oxide layers, the main wear mechanism observed was adhesive. The work carried out confirmed the potential of laser quenching in the surface hardening of mould steels.