Characterization and hardness enhancement of amorphous Fe-based metallic glass laser cladded on nickel-free stainless steel for biomedical implant application

Amorphous metals – or Metallic Glass (MG) – have a great potential in bone implant applications because of their exceptional mechanical properties, excellent tribological and corrosion resistance characteristics, and good biocompatibility. An upcoming trend is to develop an amorphous metallic coating on different metallic alloys to promote the hardness of crystalline metallic alloys. In this work, Fe-based amorphous – FeCrMoCB – coating was developed on nickel-free stainless-steel substrate using laser cladding (LC) technique at two laser power levels (1500 and 2000 W) with different scanning speeds to enhance the hardness of the crystalline metallic substrate. Scanning electron microscope (SEM) and X-ray diffraction (XRD) examinations confirmed the formation of both the amorphous structure phase at the coating layer (CL) and crystalline structure phase at the transition layer (TL) at the interface. The experimental results showed that all specimens confirmed amorphous CL. However, at relatively low speed, 5 mm/s at 1500 W and 15 mm/s at 2000 W, the CL exhibited higher crystallinity within the amorphous structure. The micro-hardness was extremely high within higher amorphous content (up to 1300 HV0.1), while the hardness value was degraded when higher crystallinity existed (900 HV0.1). It was noticed that for similar CL microstructure and hardness values, increasing the laser power by 33.33% exhibited increasing the scanning speed by 150%–200%. This indicates the significant effect of the laser power on the microstructure and the hardness of the CL. In addition, the laser power and scanning speed has an interaction effect on the CL developed.