Development of Mo-Ni-Si-B metallic glass with high thermal stability and H versus E ratios

We report a novel Mo-Ni-Si-B metallic glass which can be solidified into fully amorphous state by melt-spinning process, with high crystallization onset temperature of over 1100 K, extremely high Vickers hardness of 27.5 ± 2.2 GPa and relatively low Young's modulus of 364.3 ± 6.6 GPa. The dense cluster-packing model suggests that the addition of boron up to 10 at.% can occupy vacant cluster-interstices of (Mo, Ni)-Si cluster arrays, which results in a more efficiently dense-packed cluster structure, destabilizes the formation of nanocrystalline phases, and systematically increases the glass-forming ability (GFA) in Mo-Ni-Si-B alloys. The GFA parameters that do not directly rely on T_g, such as ΔT* and ε parameter, show greater reliability to evaluate GFA for Mo-Ni-Si-B metallic glass exhibiting no clear T_g. The H/E and H²/(2E) ratios of the newly developed Mo-Ni-Si-B metallic glass, which reflect wear resistance and resilience, exhibit the highest values among various hard ceramic materials as well as metallic glass-forming alloys developed up to now. These advantages of Mo-Ni-Si-B metallic glass can be used more widely to form a high temperature wear-resistant coating layer on various substrates. Furthermore, the same idea might be used to form a metallic glass-nitride nanocomposite coating layer by reactive deposition in N₂ ambient, with highly lubricative property and high wear-resistance, especially at high temperature.