[en] In this study, 45 carbon steels were boronized, borosulphurized and RE-borosulphurized at 950 °C for 6 h, respectively. The samples were then characterized by scanning electron microscopy, X-ray diffraction, Auger electron spectroscopy, microhardness tester and ring-on-block wear tester. It has shown that the diffusion front (the interface between the diffusion layer and the substrate) of the boride layer (BL) and the boro-sulfide layer (BSL) is saw tooth shape, while the diffusion front of the RE-boro-sulfide layer (RBSL) is flat. Compared with BSL layer, RBSL layer has a smaller and more uniform grain size, and a flatter hardness gradient from the surface to the diffusion front. The RBSL layer, consisting of an outer layer (from surface to 30 μm) mainly composed of Fe-B and an inner layer (from 30 μm to the diffusion front) mainly composed of Fe-S, has the best wear resistance and the most sufficient adhesion among those three.

[en] Highlights: • The interface changes flatter and flatter with the increase of Na_2S_2O_3. • The content of B in the surface of the coatings increases with Na_2S_2O_3 increase. • The amount of the Fe_2B phase decreases with the increase of Na_2S_2O_3 content. • The wear resistant of the B-3SL layer is the best when a high load is applied. - Abstract: In this study, the effect of Na_2S_2O_3 on RE-boronizing behavior of 45 carbon steel was investigated by varying the Na_2S_2O_3 content in the treatment agent. The content of Na_2S_2O_3 was set to 0%, 1%, 2%, 3%, 4% and 5%, respectively, to study the effect of sulfur on the property of the boride layer. The diffusion layers obtained by the above-described agents containing different levels of Na_2S_2O_3 were named B-0SL, B-1SL, B-2SL, B-3SL, B-4SL and B-5SL, respectively. Pack RE-boronizing of 45 carbon steel was carried out at 300 °C for 2 h, and then at 850 °C for 6 h. The diffusion coatings were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Vickers microhardness measurement, profilometry, the Daimler-Benz Rockwell-C adhesion test, and friction test. Testing results have revealed a significant morphology change in the borides with different Na_2S_2O_3 contents. The thickness of the layer increases dramatically with increasing content of Na_2S_2O_3, reaches its maximum (152 μm) with an agent of 3 wt.% Na_2S_2O_3, then remains unchanged with further increasing Na_2S_2O_3 content. The concentrations of B, S and O in the diffusion coatings increase with increasing the content of Na_2S_2O_3. B-rich, O-rich and S-rich regions form successively from the surface to the inner layer in the B-5SL layer. FeS_2 and Fe_2O_3 phases with a low hardness were observed in the B-3SL and B-5SL layers, respectively. The microhardness of the B-5SL layer is the highest, while the adhesion between the coating and the substrate in the B-3SL layer is the best among all the coatings. Compared with other coatings, the B-3SL layer can still keep a lower friction coefficient as well as a lower wear rate even when a high load is applied

[en] CoNi nanotubes were prepared in pores of anodic aluminum oxide templates via a dc electrodeposition method. The dependence of product morphology on the applied potential was studied over the range −1.0 to −2.5 V. The results showed that a critical potential related to the electrodeposition parameters exists, below which the deposited product was almost entirely in the form of nanotubes, whereas above which, nanowires are formed. Magnetic measurements showed hysteresis loops of the nanotubes are discontinuous. Theoretical analysis suggested the existence of some peculiar magnetization configuration such as vertical Bloch line which was responsible for the discontinuity of the hysteresis loops. - Highlights: • CoNi nanotubes were successfully prepared via a dc electrodeposition method. • A critical potential was offered for preparation of CoNi nanotubes. • The discontinuous hysteresis loops of the CoNi nanotubes were discussed. • The reasons for the discontinuity of the hysteresis loops were given