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Improvements to the wear performance of CD4MCu (a cast Fe-Cr-Ni-Cu-Mo duplex stainless steel grade) would be of great benefit in pump applications. This study demonstrates that CD4MCu stainless steels reinforced with (Nb0.75,Ti0.25)C particles can be fabricated by simply melting the elements required for the CD4MCu stainless steel together with the amounts of Nb, Ti and C required to achieve a specific volume fraction of (Nb0.75,Ti0.25)C particles in a miniature laboratory argon arc furnace. Their potential as erosion resistant materials was evaluated through microstructural characterization, hardness testing, and sliding wear tests. The formation of (Nb0.75,Ti0.25)C particles was found to improve the bulk hardness of the CD4MCu stainless steels without significantly altering its duplex microstructure, which then led to better wear performance. The results indicate that large-scale casting of the proposed materials should be possible and that they have potential as erosion resistant materials.

This chapter presents micro-structural, mechanical and tribological characterisations of additively manufactured continuous carbon fibre reinforced polyamide 6 (CF/PA6) composites, highlighting the adverse effect of microscopic voids by comparing the properties of the 3D printed composites with those of the same composites after further compression moulding. The results indicate the essential need for the further development of FFF technique to reduce the void content within the composites fabricated by the FFF process.

In the present work, continuous carbon fibre (CCF) reinforced polyamide 6 (PA6) composites were fabricated using the Fused Filament Fabrication (FFF) 3D printing technique. The sliding friction and wear behaviour of the printed CCF/PA6 composites was investigated as a function of varying fibre orientations (i.e. normal, parallel, and anti-parallel) and layer deposition directions (i.e. parallel and perpendicular) with respect to the sliding direction. It emerged that fibre orientation played a key role in determining the wear resistance of 3D printed composites. Severe fibre breakage was observed when the orientation of fibre was in normal direction against the sliding direction, associated with a higher wear rate than that obtained in parallel or anti-parallel direction. To better understand the effects of voids on wear mechanism, tribo-tests were further carried out with the specimens that underwent compression moulding (CM) post-treatment process. The results confirmed that the internal defects could cause adverse impacts on wear performance, depending on the fibre orientations. In particular, it was found that fibre distribution, as well as the fibre/matrix interface within the filament, was the crucial parameter affecting the overall tribological performance of the printed structures. The findings add to our understanding of designing and fabricating wear-resistant polymer composites using 3D printing technologies.

In this study, the tribological properties of an AlSi10Mg alloy that was fabricated using laser powder bed fusion, an additive manufacturing technique, was investigated in both the as-built (but stress-relieved) and T6-treated condition. The stress-relieved condition consists of elongated Al grains and a dendritically-arranged nano-crystalline Si-phase. T6 treatment, a conventional heat treatment for cast AlSi10Mg alloys, caused this Si phase to dissolve, re-precipitate and coarsen, which resulted in a loss of hardness, toughness and strength. Dry sliding wear tests were conducted against both a bearing stainless steel and a much harder SiC, and with the sliding direction either perpendicular or parallel to the building direction. In almost all conditions it was found that the T6 treatment either had no statistically significant effect on the wear rate or was detrimental.