Hierarchical nanostructured W-Cu composite with outstanding hardness and wear resistance

Abstract

Hierarchical nanostructured W-Cu composite with an average W size below 200 nm and nanocrystalline structure inside the W phase was obtained by refining the inner structure of the initial ultrafine powders combined with high-pressure spark plasma sintering. It revealed that an atomic scale combination can be formed at both the W grain boundaries and W/Cu interfaces. Accordingly, the nanostructured W-Cu composite exhibits twofold hardness and greatly improved wear resistance with satisfactory electrical conductivity, as compared to those of their fine grain structured counterparts. The upgraded wear resistance is attributed to the restricted micro-plowing and the mechanically mixed layer, induced by a refined microstructure, intrinsic high hardness, and the composition modulation on the wear surface.

Effect of Grain Refinement on the Comprehensive Mechanical Performance of W–Cu Composites

“…However, the debris on the UFG W–Cu composite were much smaller than that in the CCG W–Cu composite, which further led to much narrower grooves in the UFG W–Cu composite, since grooves were typically caused by the scratches of the worn debris. It can then be concluded that abrasive wear and fatigue wear are the dominant wear mechanisms for both UFG W–Cu and CCG W–Cu composites, which is also consistent with previously reported results [ 29 ].…”

“…For both the UFG and CCG W–Cu composites, significant pile-ups can be found at both ends of the wear scar due to plastic deformation. However, the pile-ups of the CCG W–Cu composite were much larger than that in the UFG W–Cu composite because the UFG W–Cu had higher hardness and greater resistance to deformation [ 29 ]. In addition, the width and depth of the wear scar for the UFG W–Cu composite (0.69 mm, 25.65 μm) were also much smaller than that of the CCG W–Cu (0.78 mm, 32.82 μm), indicating a reduced wear rate.…”

“…That is, only deformation occurred in the plastic deformation zone, while severe oxidation occurred in the mechanical mixing zone. According to our previous study, the MML was mainly composed of oxides of tungsten and copper [ 29 ]. Significantly, the thickness of the MML and plastic deformation zone in the CCG W–Cu composite can be more than 5 μm, which was more than two times that of the UFG W–Cu composite (less than 2 μm).…”

“…In addition, ultrahigh high-temperature strength was achieved in nanostructured W–Cu–Cr–ZrC composites [ 28 ]. The wear resistance of nanostructured W–Cu composites was also largely improved [ 29 ]. Unfortunately, a large number of phase interfaces in nanocrystalline W–Cu also cause a decrease in electrical conductivity [ 29 ].…”

“…The wear resistance of nanostructured W–Cu composites was also largely improved [ 29 ]. Unfortunately, a large number of phase interfaces in nanocrystalline W–Cu also cause a decrease in electrical conductivity [ 29 ]. Therefore, achieving the combined enhancement of wear resistance and high-temperature strength with a nonsignificant decrease in conductivity remains challenging.…”