The influence of 3D-printed PLA coatings on pure and fretting fatigue properties of AM60 magnesium alloys under cyclic bending loads

A study was conducted to compare the pure fatigue and fretting fatigue properties of AM60 magnesium alloys, with and without 3D-printed PLA coatings. The PLA coating layers led to an increase in the fatigue lifetime in both pure and fretting conditions. They delayed the crack initiation time compared to uncoated samples, thereby increasing fatigue lifetime. Additionally, in the case of fretting fatigue, PLA coating caused the fretting pads to reach the magnesium alloy later, which also contributed to the longer lifetime of coated samples, compared to uncoated specimens. Using field emission scanning electron microscopy, all specimens exhibited the brittle fracture behavior, with the presence of both cleavage and quasi-cleavage marks. By the fractography, it was found that the number of cracks in coated samples decreased in both pure and fretting fatigue conditions. Remarkably, PLA coating during fretting fatigue resulted in a significant enhancement of the fretting fatigue lifetime, within 56%–2182 %.