Graphite‐MoS2‐Fe2O3 (Fe3O4) nano‐composite lubricating coatings were prepared on the surfaces of non‐copper coated solid wires by a mechanical coating technique. The tribological behaviours of graphite‐MoS2‐Fe2O3 (Fe3O4) coatings at the rubbing interfaces of welding wires against the contact tube were investigated. The results demonstrate that the lubricating properties of graphite‐Fe3O4 coatings outperform the lubricating properties of graphite‐Fe2O3 coatings. The anti‐wear performance of the contact tube is strengthened with increasing nano‐MoS2 contents. Layers of protective tribofilms are formed at the rubbing interfaces of welding wires against a contact tube by tribochemical reaction among lubricants. The tribofilms are composed of FeO, MoO3 and FeMoO4 with excellent lubricating properties. They can avoid direct contact of welding wires against the contact tube, thus decreasing contact tube wear. With the transition of the contact tube wear from mild to severe, the dominant wear mechanisms of contact tube change from fatigue peeling and oxidative wear to abrasive wear and arc ablation.
The effect of nano and microstructured powders in cored wires on formation and properties of Fe-TiB2 composite coatings by high velocity arc spraying (HVAS) was investigated. Six cored wires filled with different average ceramic particle sizes (20-40 nm, 2 µm, and 420 µm) and fine powder contents (0, 8, 16, 20, 24, 32wt.%) were sprayed. The flattening behavior of sprayed particles was characterized and compared by using optical microscopy (OM) and 3D Surface Profiler. The microstructure of the coatings and phase compositions were characterized by means of Laser Confocal Scan Microscopy, SEM, EDAX and XRD. Hardness and wear properties were evaluated. The results showed that the splat shape of the cermets has a transitional tendency to change from a distorted heavy splash to a disk with little splash with (i) increasing the percentage of fine ceramic particles and (ii) decreasing coatings porosity. Fe –2 µm 32% TiB2 coatings reveals a dispersion of fine ceramic particles and less scattering of hardness, which improved the wear resistance and changed the abrasion mode.
Al-based coating was prepared with Al-based cored wire by arc spraying. The properties of high-temperature oxidation resistance and corrosion resistance of Al-based coating were compared with those of Fe-Al coating and 45CT coating. The property of H2S corrosion resistance of Al-based coating was compared with that of A304 stainless steel and Fe-Al coating. The results suggest that the Al-based coating has better properties of high-temperature oxidation resistance and corrosion resistance than Fe-Al coating and 45CT coating. Al-based coating has better property of H2S corrosion resistance than A304 stainless steel and Fe-Al coating.
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