Influence of Chemical Composition and Water Quenching on the Phase Constitution, Microstructure and Dry-Sliding Wear of Zr-10Nb-xMo (x = 0, 2 and 4 wt.%) Alloys

Zirconium-based alloys are considered promising candidates for biomedical applications due to their favorable mechanical properties and corrosion resistance. In this study, Zr-10Nb-XMo alloys (X = 0; 2; and 4 wt.%) were fabricated using a combination of powder metallurgy and arc melting, followed by water quenching, in order to evaluate the effect of molybdenum addition and heat treatment on their microstructure and tribological behavior. Phase composition was analyzed by X-ray diffraction, while microstructural features were examined using optical and scanning electron microscopy. Tribological properties were assessed under dry sliding conditions using a reciprocating tribometer. XRD analysis revealed the presence of two Zr-Nb solid-solution phases for all investigated compositions, with no additional phases detected within the sensitivity of the method. Rietveld refinement showed that water quenching increased the fraction of the hexagonal phase from about 50 to about 60 wt.% and increased the lattice parameters of both phases, whereas Mo addition mainly decreased the lattice parameter of the cubic phase. Increasing molybdenum content and water quenching were associated with changes in microstructural morphology, including the appearance of finer, needle-like features in some quenched specimens. The lowest mean specific wear rate was recorded for the water-quenched Zr-10Nb-4Mo alloy (6.4 × 10−4 mm3/(N·m)), compared with 10.5 × 10−4 mm3/(N·m) for the initial Zr-10Nb alloy. The lower mean wear coincided with higher indentation hardness and changes in microstructural morphology. However, the present results do not establish a direct causal relationship between these characteristics. The results suggest that molybdenum addition combined with controlled heat treatment may provide a promising approach for modifying the microstructure and dry-sliding wear behavior of Zr-Nb-based alloys. Further investigations are required to confirm the reproducibility of the observed trends and evaluate their potential biomedical applications.