Analyses of the sliding wear behavior of NiTi shape memory alloys fabricated by laser powder bed fusion based on orthogonal experiments

Laser powder bed fusion of NiTi (LPBF-NiTi) alloys is gaining increasing attention and applications because of its flexible design for complex structures with excellent superelasticity and shape memory effects. Their wear behavior has a strong influence on the serviceability and safety, but the effects of their usage condition on the wear behavior are not clarified clearly. In the present work, the wear resistance of LPBF-NiTi (55.4 wt%Ni) alloys against 100Cr6 steel on a ball-on-slab tribometer and its response to sliding speed, normal load and sliding time were studied through orthogonal experiments. The results confirm that the wear rate of LPBF-NiTi alloys ranges from 1.1-2.5 x 10-3 mm3/m, which is comparable to that of NiTi alloys fabricated by conventional methods. In addition, the sliding speed has the largest influence with a range of 5.1 x 10-5 mm3/Nm, followed by normal load with a range of 4.2 x 10-5 mm3/Nm. The effect of the interaction between the normal load and sliding speed is significantly greater than the effect of the sliding time. Finally, the wear mechanism of the worn surface and microstructure of the subsurface under the wear track were discussed in detail. The dominant wear modes are adhesion, abrasion and delamination.