Search Results (15)

Wear-resistant coatings applied to the surface of copper and copper alloys through diverse advanced technologies can substantially enhance their wear resistance and broaden their application spectrum. This paper provides a comprehensive review of the development and current research status of wear-resistant coatings fabricated on copper and its alloys. It presents the research findings on the preparation of wear-resistant coatings using both one-step methods (such as laser cladding, electroplating, thermal spraying, cold spraying, electro-spark deposition, etc.) and two-step methods (chemical plating and heat treatment, electrodeposition and laser cladding, laser cladding and in situ synthesis, etc.). This paper provides an in-depth examination of the characteristics, operating principles, and effects of various coating techniques on enhancing the wear resistance of copper and copper alloys. The advantages and disadvantages of different coating preparation methods are compared and analyzed; meanwhile, a prospective outlook on the future development trends is also offered. Full article

The article presents research results on the possibility of shaping the structure and properties of Co-Cr-W-C-Ti alloys (type Stellite 6) using laser cladding technology. Cobalt-based alloys are used in several industries because they are characterized by high erosion, abrasion, and corrosion resistance, retaining these properties at high temperatures. To further increase erosion resistance, it seems appropriate to reinforce material by in situ synthesis of hard phases. Among the transition metal carbides (TMCs), titanium carbide is one of the hardest and can have a positive effect on the extension of the lifetime of components made from cobalt-based alloys. In this article, concentration of C, W, and Ti due to the possibility of in situ synthesis of titanium carbides was subjected to detailed analysis. The provided research includes macrostructure and microstructure analysis, X-ray diffraction (XRD), microhardness, and penetrant tests. It was found that the optimal concentrations of Ti and C in the Co-Cr-W-C alloy allow the formation of titanium carbides, which significantly improves erosion resistance for low impact angles. Depending on the concentrations of titanium, carbon, and tungsten in the molten metal pool, it is possible to shape the alloy structure by influencing to morphology and size of the reinforcing phase in the form of the complex carbide (Ti,W)C. Full article

In this study, homogeneous (Ti, Nb)(C, B)/IN625 composite coatings with almost defect-free microstructures were successfully prepared on a 42CrMo steel substrate by coupling ultra-high-speed laser cladding (USLC) with the direct reaction synthesis (DRS) technique to introduce the in-situ exothermic reaction into the cladding materials; these were comparatively analyzed with the pure IN625 coating prepared only by USLC. Our results showed that the interface of the composite coating/substrate was greatly affected by about 670 kJ Joule heat released from the in-situ reaction happening during the cladding process, which was sufficient to remelt the as-deposited materials and significantly increased the coating/substrate interface width to around 24 μm, six times the interface width of pure IN625 coating. Furthermore, the residual stress inside the coating and across the interfacial region was also reduced, alleviating the interface stress mismatch. However, the surface hardness of (Ti, Nb)(C, B)/IN625 composite coating was found to be lower than that of the IN625 coating, and the average wear weight loss was only 10% of that of the IN625 coating, attributable to the in-situ authigenic TiCB, TiC, NbMo₃B₄ and NbMo₂B₂ phases providing load transfer from the hard phases to the IN625 composite matrix to achieve abrasion reduction and wear resistance. It was also found that the formation of nano-equiaxial ultrafine grains in the depth range of 250 nm below the wear surface was facilitated by the coupling of the three fields of plastic rheology-heat-force, which dynamically strengthened the wear surface. Based on these findings, it is suggested to promote the strategy of combing USLC and DRS techniques to achieve an additional ability to enhance the coating microstructure and reduce residual stress, to achieve better tribological performance. Full article

In situ NbC-reinforced laser cladding Ni45 coatings have the advantages of high bond strengths, low dilution rates, small heat-affected zones and good wear resistance and have broad application prospects in the field of surface strengthening and repair of workpieces such as automotive molds and engine turbines. Previous studies have mostly used pure niobium powder for in situ synthesis to prepare Ni-based NbC coatings with a high production cost. In this paper, NbC was successfully synthesized in situ in Ni45 powder using inexpensive FeNb65 and Cr3C2. The prepared coating has a uniform microstructure and excellent wear resistance, and the reinforced phases are mainly NbC and Cr23C6. Coating 4# with 25 wt.% FeNb65 + Cr3C2 has the highest microhardness of 776.3HV0.2, about 1.45 times that of the Ni45 coating, and its wear resistance is 36.36 min/mg, about 60.6 times that of the Cr12MoV steel base material and about 23.76 times that of the Ni45 coating. Full article

With the use of electrolytic Cu powder, Zr powder, Si powder and nickel-coated B₄C powder as cladding powders, in-situ synthesized ZrB₂-SiC reinforced copper matrix composite coatings were prepared by laser cladding on the surface of the copper substrate to improve the surface hardness and wear resistance. Under the condition of a laser energy density at 60 kJ/cm², the macroscopic surface of the composite coating was continuously flat. The microstructure and phase of the cladding coating were analyzed by means of XRD and SEM. The reinforcements with nano-scale particle and micron-scale needle-like structures were in-situ synthesized in the cladding coating, and the content of the reinforcement phase decreased slightly from the coating surface to the substrate. The phase analysis results showed that the reinforcements included ZrB₂ and SiC. When the content of the reinforcement was increased to 30 wt%, microhardness also increased from 48 HV_0.2 to 309 HV_0.2, which was about 5.6 times that of the copper matrix. The wear resistance of the composite coatings was characterized by current-carrying wear tests. By keeping the sliding speed and load constant, the wear rate decreased with an increase in the reinforcement content, and the wear mechanism changed from adhesive wear to abrasive wear. The wear rate of the composite coating with the current was higher than that without the current due to its electric ablation and high temperature. Full article

Carbon nanodots (CNDs) are interesting materials due to their intrinsic fluorescence, electron-transfer properties, and low toxicity. Here, we report a sustainable, cheap, and scalable methodology to obtain CNDs from sugarcane syrup using a domestic microwave oven. The CNDs were characterized by infrared spectroscopy, dynamic light scattering, atomic force microscopy, absorption, and emission spectroscopies. The CNDs have 3 nm in diameter with low polydispersity and are fluorescent. A fluorescent hydrogel–CNDs composite was obtained using gelatin polypeptide as the polymeric matrix. The new hydrogel–CNDs composite was incorporated in the cavities of a double-clad optical fiber using an innovative approach that resulted in a microstructured polymer optical fiber with intrinsic fluorescence. This work shows a promising alternative for the fabrication of fluorescent materials since the CNDs synthesis is sustainable and environmentally friendly. These CNDs might substitute the rare-earth and other heavy metals of high cost and toxicity, which are usually incorporated in double-clad fibers for applications on lasers, amplifiers, and spectroscopy. Full article

To improve the wear and corrosion resistance of the pump barrel material (40Cr steel), a (M:Nb,Ta)C/Ni35 composite cladding coating by in situ synthesis of composite carbides was conducted. The effects of ceramic micro-particles content on the phase composition, microstructure of the coating, structural characteristics of (M:Nb,Ta)C and the tribology and electrochemical corrosion behavior were systematically studied. The increase of ceramic micro-particles changed the morphology of (M:Nb,Ta)C with the size from sub-micron to micron. The (M:Nb,Ta)C dispersed along the grain boundary inhibits the growth of the grains. During friction, the spherical structure exhibited a rolling lubrication effect and the petal structure provided a stronger attachment ability to resist the shear. The corrosion occurred at the grains, exhibiting corrosion pits, in which the high content ceramic micro-particles were relatively shallow. Moreover, a few dot corrosion pits were distributed along the grain boundaries without (M:Nb,Ta)C. Therefore, to improve the corrosion resistance, a thin composite carbide coating with good wear and corrosion resistance was prepared. Full article

Boride-based cermet can serve as a good protective coating for low-corrosion and wear-resistant materials, such as carbon steels, due to their mechanical and chemical properties. In this study, M₃B₂ (M: Mo, Ni, Fe, and Cr) boride-based cermet coatings were fabricated on Q235 steel with mixed powders of Mo, B, Ni60, and Cr by laser cladding synthesis, and the effects of laser power on the properties of the cermet layer were investigated. Three laser powers (2200, 2500, and 2800 W) were used at the same scanning speed. The X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) analysis confirmed that all the coatings were composed of M₃B₂-type borides and {Fe, Ni} alloys. The micro-hardness, corrosion, and frictional experiments showed that the cermet coatings enhanced the corresponding performances of the Q235 steels at the three laser powers. However, the micro-hardness of the coatings decreased as the power increased, and the maximum micro-hardness value was 1166.3 HV (Vickers Hardness). The results of the corrosion and frictional experiments showed that the best performance was obtained at a laser power of 2500 W, followed by 2800 and 2200 W. Full article

The hard and corrosion resistant coatings of Mo₂NiB₂ cermet were prepared by the laser cladding technique. The influences of the Mo:B ratio and the laser scanning speed on the microstructure and property of the Mo₂NiB₂ cermet coatings were investigated. The results showed that the laser scanning speed of 1.5 mm/s and the Mo:B ratio of 1 were more beneficial to the formation of Mo₂NiB₂ cermet than 2.0 mm/s and 0.8, 1.2, respectively. The amount of the Mo₂NiB₂ ceramic phases were decreased from the top layer to the bottom layer of the coating. The changes of microstructure and composition led to the changes of hardness and corrosion resistance of the Mo₂NiB₂ cermet coatings. The coating prepared at the Mo:B ratio of 1 and the scanning speed of 1.5 mm/s possessed the highest hardness, and the hardness gradually decreased from the top layer to the bottom layer of the coating. The formation of Mo₂NiB₂ and {FeM} phases led to the enhanced corrosion resistance of the Mo₂NiB₂ cermet coatings, and the coating prepared at the Mo:B ratio of 0.8 possessed the best corrosion resistance and the minimum corrosion current. Full article

Although Q235 steel materials are widely used in offshore engineering, the service life is severely shortened by its inferior resistance to wear and corrosion in harsh marine working environments. Boride-based cermet composites could be a good surface-protective coating to enhance surface hardness, wear resistance, and corrosion resistance. M₃B₂ (M: Mo, Ni, Fe, Cr) boride-based cermet coatings composed of hard ceramics of M₃B₂-type complex borides and an {Fe, Ni} metal matrix was fabricated on Q235 steels with mixed Mo, Cr, B, and Ni60 powders using a laser cladding synthesis technique. The influences of laser cladding parameters on the microstructure, phase composition, microhardness, and corrosion resistance of the coatings were comprehensively investigated. Results showed that the microstructures of the coatings mainly consisted of three layers, which were, from the top to bottom layer, a metal layer with fewer ceramic phases, a ceramic layer with fewer metal phases, and another metal layer with fewer ceramic phases. The ceramic phases were mainly M₃B₂-type borides, and the metal phases were mainly {Fe, Ni} alloys. The appearance of Fe-enriching metal phases was due to the supply of Fe elements from Q235 substrates. With squash pretreatment and without a remelting aftertreatment, ceramics uniformly dispersed in the cermet coatings, and their sizes decreased. The results of microhardness showed that the microhardness of the coating first increased and then decreased from the top layer to the bottom layer, and maximum microhardness was obtained in the layer of ceramics with less metal phases. An electrochemical corrosion test showed that the cermet coatings (j_corr = 6.35 μA/cm²) could improve the corrosion resistance of Q235 steels (j = 43.76 μA/cm²) by one order of magnitude. Full article

AlCoCrFeNiNb_x (x in molar ratio x = 0, 0.25, 0.5, 0.75, and 1.0) high-entropy alloy (HEA) coatings were manufactured on 304 stainless steel by laser cladding. The constituent phases, microstructures, chemical composition, micro-hardness and wear resistance of the HEA coatings were investigated respectively by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), a Vickers hardness tester and a friction/wear testing machine. It was found that an AlCoCrFeNi alloy coating without Nb consisted of body-centered-cubic (BCC) and order BCC (B2) phases, while the AlCoCrFeNiNb_x (x > 0) alloy coatings consisted of BCC, B2 and Laves phases. Microstructures of the AlCoCrFeNiNb_x alloy coatings evolved from equiaxed grain (x = 0) to hypoeutectic (0.25 ≤ x < 0.75), then to full eutectic (x = 0.75), and finally to hypereutectic (x > 0.75). With increasing Nb content, the Vickers hardness values increased. AlCoCrFeNiNb_0.75 alloy coating with a fully eutectic microstructure demonstrated the best wear resistance among the AlCoCrFeNiNb_x (x ≥ 0) alloy coatings. Full article

Using Ni60 alloy, C, TiN and Mo mixed powders as the precursor materials, in situ synthesized Ti(C,N) particles reinforcing Ni-based composite coatings are produced on Ti6Al4V alloys by laser cladding. Phase constituents, microstructures and wear properties of the composite coatings with 0 wt % Mo, 4 wt % Mo and 8 wt % Mo additions are studied comparatively. Results indicate that Ti(C,N) is formed by the in situ metallurgical reaction, the (Ti,Mo)(C,N) rim phase surrounding the Ti(C,N) ceramic particle is synthesized with the addition of Mo, and the increase of Mo content is beneficial to improve the wear properties of the cladding coatings. Because of the effect of Mo, the grains are remarkably refined and a unique core-rim structure that is uniformly dispersed in the matrix appears; meanwhile, the composite coatings with Mo addition exhibit high hardness and excellent wear resistance due to the comprehensive action of dispersion strengthening, fine grain strengthening and solid solution strengthening. Full article

The Laser Engineered Net Shaping (LENS) technique was combined with direct synthesis to fabricate L2₁-ordered Fe-Al-Ti based intermetallic alloys. It was found that ternary Fe-Al-Ti alloys can be synthesized using the LENS technique from a feedstock composed of a pre-alloyed Fe-Al powder and elemental Ti powder. The obtained average compositions of the ternary alloys after the laser deposition and subsequent annealing were quite close to the nominal compositions, but the distributions of the elements in the annealed samples recorded over a large area were inhomogeneous. No traces of pure Ti were observed in the deposited alloys. Macroscopic cracking and porosity were observed in all investigated alloys. The amount of porosity in the samples was less than 1.2 vol. %. It seems that the porosity originates from the porous pre-alloyed Fe-Al powders. Single-phase (L2₁), two-phase (L2₁-C14) and multiphase (L2₁-A2-C14) Fe-Al-Ti intermetallic alloys were obtained from the direct laser synthesis and annealing process. The most prominent feature of the ternary Fe-Al-Ti intermetallics synthesized by the LENS method is their fine-grained structure. The grain size is in the range of 3–5 μm, indicating grain refinement effect through the highly rapid cooling of the LENS process. The Fe-Al-Ti alloys synthesized by LENS and annealed at 1000 °C in the single-phase B2 region were prone to an essential grain growth. In contrast, the alloys annealed at 1000 °C in the two-phase L2₁-C14 region exhibited almost constant grain size values after the high-temperature annealing. Full article

In the paper, we report on the development of a synthesis and melting method of phosphate glasses designed for active microstructured fiber manufacturing. Non-doped glass synthesized in a P₂O₅-Al₂O₃-BaO-ZnO-MgO-Na₂O oxide system served as the matrix material; meanwhile, the glass was doped with 6 mol% (18 wt%) of Yb₂O₃, as fiber core. The glasses were well-fitted in relation to optical (refractive index) and thermal proprieties (thermal expansion coefficient, rheology). The fiber with the Yb³⁺-doped core, with a wide internal photonic microstructure for a laser pump, as well as with a high relative hole size in the photonic outer air-cladding, was produced. The laser built on the basis of this fiber enabled achieving 8.07 W of output power with 20.5% slope efficiency against the launched pump power, in single-mode operation M² = 1.59, from a 53 cm-long cavity. Full article

Intermetallide phase formation was studied in a powdered Fe–Al system under layer by layer laser cladding with the aim of fabricating the gradient of properties by means of changing the Fe–Al concentration ratio in the powder mixture from layer to layer. The relationships between the laser cladding parameters and the intermetallic phase structures in the consecutively cladded layers were determined. In order to study the structure formation an optical microscopy, X-ray diffraction analysis, measurement of microhardness, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy analysis were used after the laser synthesis of intermetallic compounds. Full article