Gradient hardening of 60NiTi alloy by forced water-cooled laser surface quenching

60NiTi alloy is a promising candidate for aerospace bearings; however, homogeneously heat-treated 60NiTi fails to simultaneously satisfy the requirements of impact resistance and wear resistance, which limits its practical application. Herein, a novel forced water-cooled laser surface quenching technique is proposed to fabricate a hardness gradient in impact-resistant 60NiTi alloy, enhancing its surface wear resistance. The efficacy of this approach was validated by investigating the effects of laser temperature and cooling methods. We find that forced water-cooled induces a microstructural gradient along the depth direction, characterized by the gradual increase of Ni₃Ti phase, the growth of Ni₄Ti₃ phase. This microstructural gradient enhances the surface hardness to 624.29 HV_0.2, which is 2.26 times higher than that of the sample core (275.78 HV_0.2), and reduces the friction coefficient to 0.39 (compared with 0.96 of un-LSQ sample). This approach offers novel ideas for the development of aerospace bearing of withstanding complex service conditions.