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Laser directed energy deposition (LDED) was utilized to incorporate carbon nanotubes (CNTs) into WE43 magnesium alloy, aiming to enhance its wear resistance by leveraging the exceptional mechanical and self-lubricating properties of CNTs. The LDED-prepared CNTs reinforced WE43 composite (CNTs/WE43) coatings were fabricated for evaluating the wear resistance improvement. The microstructure and wear properties of the LDED-prepared CNTs reinforced WE43 composite coating were investigated in comparison to the WE43 coating. The addition of Ni coated CNTs (Ni-CNTs) led to drastic morphologic changes including the emergence of stratified structures and distinct furrow formations. The composite coating exhibited altered segregation patterns, characterized by the presence of filamentous, punctiform, porphyritic, and ring-shaped accumulations of CNTs, Mg 24 Y 5 , and Zr cores in both the central and furrow zones. The addition of Ni-CNTs induced a decrease of up to 45.8 % in wear weight loss for the WE43 coating. The friction coefficient versus the applied loads of the WE43 and CNTs/WE43 coatings showed an opposite trend. The incorporation of CNTs significantly improved the wear resistance of the WE43 coating by enhancing its ability to resist plastic deformation, forming a protective carbon film, and providing self-lubricating effects. • Successful fabrication of CNTs/WE43 composites via laser directed energy deposition • Unique altered segregation patterns in the composite coatings • Self-lubricating and strengthening effects of CNTs for improving the wear resistance • Friction coefficient of the WE43 and composite coatings showed an opposite trend. [ABSTRACT FROM AUTHOR]

The microstructure evolution in the fusion zone of laser-welded Mg-Gd-Y-Zr alloy during solution and aging treatment is investigated. The morphology of the Mg 24 (Gd,Y) 5 in the divorced eutectic at the grain boundary transforms from a continuous network to disconnected and fragmentized islands and then to spheroidal particles before complete dissolution during the solution treatment at 430 °C. During the subsequent aging treatment at 225 °C, the precipitation sequence in the fusion zone follows the order of supersaturated solid solution (SSSS) → βʺ(D0 19 ) → βʹ(cbco) → β 1 (fcc) → β(fcc). High-density precipitates are present at the original grain boundaries of the fusion zone from the welded structure but there are less precipitates in the interior of the original grains. The grain growth during the solution treatment at 430 °C comprises the slowly increasing stage, rapidly increasing stage, and stable stage. The network-distributed Mg 24 (Gd,Y) 5 impedes migration of the grain boundaries, restricts grain growth in the first slowly increasing stage, and segregation of zirconium near the grain boundaries also affects migration of the grain boundaries. [ABSTRACT FROM AUTHOR]

• The coatings are fabricated with TiC and Ni60 mixture powders as raw materials by laser cladding. • The effect of TiC content on microstructure and properties of TiC/Ni60 coatings is revealed. In this study, the composite coatings on Ti6Al4V alloy are fabricated with TiC and Ni60 mixture powders by laser cladding. The effect of TiC content on microstructure and properties of the coatings is investigated. Many TiC particles in large size are randomly distributed in the coatings. The coatings mainly contain TiC. TiC, TiC x , Ti 2 Ni, TiNi, TiB, Cr x B and Ti phase identified by XRD. The feature of the precipitates in the coatings is various due to different TiC. The forms of the precipitates are changed in the coatings with increasing the TiC content. The wear resistance of the coatings decreases with increasing the TiC content. Numerous plowing grooves with the debris particles and white scaly patterns are found in the sliding direction. With increasing the TiC content, the bending strength of the samples decreases. The brittle fracture feature are shown on the fracture surface of the coatings. [ABSTRACT FROM AUTHOR]