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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. [ABSTRACT FROM AUTHOR]

Abstract AISI 440B martensitic stainless steels reinforced with up to 15 vol% NbC particles were successfully cast using a vacuum induction furnace. Energy dispersive x-ray spectroscopy, scanning electron microscopy and electron backscatter diffraction techniques revealed that NbC additions led to a slight decrease in the matrix solid solution Cr content, which was found to have a minor impact on uniform corrosion resistance. An ISO 21988 grade Cr27 martensitic eutectic white cast iron was used to benchmark the wear performance of the composites. Hardness, sliding wear tests, and erosion wear tests against a garnet slurry, showed that the composites could either match or surpass the cast iron despite having a lower total volume fraction of carbide phases. These results show that the proposed martensitic stainless steel composites have immense potential in high wear applications that require some degree of corrosion resistance, such as in the mining and mineral processing industry. Highlights • NbC - AISI 440 stainless steel composites were cast by vacuum induction melting. • NbC had a marginal effect on the corrosion resistance of AISI 440 stainless steels. • NbC was effective in improving hardness, and sliding and erosive wear resistance. • Compared to a Cr27 white cast iron alloy, the composites performed favorably. • The composites are potential alternatives to high-chromium white cast iron alloys. [ABSTRACT FROM AUTHOR]

The sliding behavior of two titanium alloys processed by laser powder bed fusion, with and without heat treatment, was investigated alongside two as-received conventionally-processed versions of these alloys. These samples presented a wide range of microstructures often encountered in Ti alloys. Oxidative, abrasive and adhesive wear always occurred when sliding against steel. However, wear rates were similar regardless of the friction and hardness if material removal mainly occurred through abrasion and/or adhesion. Martensitic phases decomposed during sliding while nano-crystalline grains enhanced oxidative wear which reduced friction. With a stable nanocrystalline microstructure that confers ultrahigh hardness, wear rate and friction can be substantially reduced by promoting oxidative over abrasive or adhesive wear. • Dry sliding of two conventionally- and LPBF-processed Ti alloys was investigated. • A nano-crystalline microstructure enhances oxide formation which reduces friction. • α′ or α″ is unstable in the presence of frictional heat and oxygen diffusion. • A stable ultrahard nanocrystalline microstructure can reduce both wear and friction. • This microstructure promotes oxidative wear and minimizes adhesion/abrasion. [ABSTRACT FROM AUTHOR]

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. • In the stress-relieved condition, the wear performance is isotropic. • Wear anisotropy occurred in the T6 condition. • The wear rate against steel is more severe than against SiC. • Frictional response is not necessarily indicative of wear performance. • T6 treatment is generally not recommended for sliding wear performance. [ABSTRACT FROM AUTHOR]

In this present work, the sliding wear behaviour of hybrid polymer nanocomposites was investigated under different loading conditions and against different counterface roughness. Two different polymers matrices, epoxy and polyamide 66, with classic micro-sized short carbon fiber and graphite flakes as tribo-fillers were investigated with and without TiO 2 reinforcing nanoparticles. It was found that the synergistic effect between nanoparticles and micro-sized fillers on friction and wear performance depended on the tribological system involved. In particular, for epoxy-based composites, the incorporation of TiO 2 nanoparticles was only beneficial against a sufficiently rough disc but detrimental otherwise. Whilst for polyamide nanocomposites, the combination of nanoparticles and other fillers resulted in low friction and wear against both rough and smooth disks, particularly at higher applied contact pressures. When the cross-sections of the transfer films were analysed using a high-resolution SEM, it was found that TiO 2 nanoparticles are only beneficial if they can blend with other wear debris to form a TiO 2 -enriched transfer film. The strengthened film provides the support required for other dislodged TiO 2 nanoparticles to achieve the rolling effect, thus reducing friction and wear. In contrast, if TiO 2 cannot effectively blend into the transfer film, TiO 2 nanoparticles act as an abrasive that readily abrades away the comparatively softer film, thus exposing the polymer to fresh asperities on the steel counterface, a detrimental outcome to both friction and wear. Hence, to design high wear resistant composite materials, it is important to understanding the interactions between different tribo-fillers for particular circumstances or contact conditions. • Polyamide and epoxy composites with and without TiO 2 nanoparticles were studied. • Depending on the tribological system, the TiO 2 may or may not be beneficial. • Improved friction and wear are due to TiO 2 -enriched transfer film formation. • TiO 2 -enriched transfer films promote the rolling effect. • TiO 2 acts as an abrasive instead if TiO 2 -enriched transfer films do not form. [ABSTRACT FROM AUTHOR]

The study of sliding wear is important as it occurs in many industrial mechanical systems. In metal-ceramic sliding wear, reinforcing the metallic counterpart with ceramic particles transforms the system from a pure metal-ceramic interaction to one that contains both metal-ceramic and ceramic-ceramic interactions, which may improve the wear performance of both materials involved. This study shows that incorporating NbC particles into a bearing stainless steel reduces its wear rate against SiC, WC and Al 2 O 3 counterparts but its wear rate remained unchanged against ZrO 2. For the ceramic counterparts, SiC and WC also experienced reduced wear while Al 2 O 3 showed negligible wear across all tests. ZrO 2 , on the other hand, experienced a very high level of wear when the stainless steel contained 5 vol% NbC but the wear rate gradually decreased as the volume fraction of NbC increased to 15 vol%. Higher NbC volume fractions are thus expected to yield further improvement. • A bearing stainless steel was subjected to sliding against SiC, WC, Al 2 O 3 and ZrO 2. • Adding NbC into the steel reduced its wear loss against SiC, WC and Al 2 O 3. • Consequently, SiC and WC also experienced a reduction in wear losses. • Al 2 O 3 experienced negligible wear across all tests. • Adding low NbC amounts to the steel is very detrimental to the wear rate of ZrO 2. [ABSTRACT FROM AUTHOR]