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In this paper the microstructural features of the glass former Fe68Cr8Mo4Nb4B16 coatings are unveiled and related to their electrochemical and tribological responses. The coating was mostly glassy with some embedded borides (M3B2, M2B-tetragonal; M being the metallic elements of the alloy) and ferrite. The tribological behavior of the HVAF coated sample, characterized by a thickness of about 200 µm, ∼6% porosity and a Vickers hardness of 357 HV0.5, was assessed in a sphere-on-plate configuration, revealing a specific wear rate of approximately 5 ×10−4 mm3∙N−1m−1. The wear mechanism was dominated by delamination caused by fragile intersplats. The corrosion resistance of HVAF coatings was evaluated in 0.6 M NaCl solution and compared with the results obtained for the crystalline Fe68Cr8Mo4Nb4B16 ingot, produced by melting in an induction furnace, and for the AISI 1020 steel substrate. The HVAF coating showed satisfactory corrosion resistance compared to the carbon steel substrate and the crystalline ingot, with the highest corrosion potential, Ecorr, values (−533 mVSCE) and the lowest corrosion current density, icorr, (10−6 A∙cm−2) followed by a clear passivation window upon anodic polarization in 0.6 M NaCl solution. Evaluations of HVAF coating showed a higher glassy content compared to the gas-atomized feedstock powders. This suggests that during spraying, certain particles were molten and experienced cooling rates adequate to inhibit crystallization, resulting in the freezing of the supercooled liquid. This phenomenon contributes to the good corrosion resistance observed in the present work and offers an opportunity to enhance the electrochemical behavior of HVAF coatings.

The development of materials with special microstructures is a continuing theme of research due to their improved physical and mechanical properties. Rapid solidification can lead to amorphous or partially crystalline microstructures, depending on the imposed processing conditions and compositions allowing the production of composite materials. Al–Ni-Sm alloys can be easily obtained in the amorphous state by rapid solidification processing so that composites could be generated depending on the cooling conditions. In this work, new results are shown for Al-based amorphous matrix composites produced during rapid solidification of Al83.5Ni10Sm6.5, Al81.5Ni10Sm6.5Pb2 and Al83.5Ni8Sm6.5Pb2 (atom percent) alloys. Lead (Pb) was added to the amorphous forming composition alloy due to its immiscibility with the main alloying elements. Ribbon samples were obtained by melt spinning technique. Besides the use of ordinary characterization techniques, such as X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), advanced transmission electron microscopy (TEM) was employed to reveal the special microstructure features forming these alloys. A strong influence of the Pb addition on crystallization behavior has been identified. Also, the size and morphology of the nanocrystalline Pb-rich minority phase within the amorphous matrix is examined. These effects were explained based on the immiscibility of Pb with the alloy components.