Surface characteristic and wear resistance of QT-700-2 nodular cast iron after laser quenching combing with shot peening treatment

Laser quenching is an effective method to improve the surface performance of steel and iron. However, temper softening in overlapping zone often exists in multi-track laser quenching process and results in non-uniform hardness and residual stress distribution in the surface of component. Here, QT-700-2 nodular cast iron (QT-700-2) was performed by laser quenching with the maximum power of 3000 W and subsequent dual shot peening. With optimized laser quenching power of 1200 W and dual shot peening intensity of 0.5 mmA +0.25 mmA, the surface characteristics and wear resistance of treated QT-700-2 were investigated. The results showed that the average residual stress and hardness values of QT-700-2 after laser quenching plus dual shot peening were increased to 564 MPa and HRC 56.8, which were 179% and 9% higher than that of samples treated only by laser quenching. Meanwhile, the uniformity of the residual stress and hardness distribution were greatly improved. Comparing the wear testing results, it found that the friction coefficient and wear scratch width of QT-700-2 after laser quenching-shot peening treatment were larger than that original matrix in the load range of 10-30 N. However, the wear loss of QT-700-2 with combined treatment of laser quenching and dual shot peening was only one-third of that for matrix. The mechanism was discussed and it can be ascribed to the formation of refined microstructure constituting martensite and graphite, high compressive residual stress and enhanced hardness in the surface layer.

Automated summary

By optimizing the laser quenching power and dual shot peening intensity, the residual stress and hardness of QT-700-2 were significantly increased, leading to an improvement in the uniformity of hardness distribution. The surface characteristics and wear resistance of the material were greatly enhanced.