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With the development of science and technology, the traditional single nickel-based coatings cannot meet the service needs of industrial parts. In this paper, the directional structure of Ni-based alloy coatings with La 2 O 3 were prepared in order to further improve the corrosion resistance of nickel-based coatings, and the effect of La 2 O 3 on microstructures and corrosion behavior of the directional structure Ni-based coatings were investigated. The results showed that with increase of La 2 O 3 content, the corrosion resistance of the composite coating shows the tendency of first increasing and then decreasing, and the optimum amount of La 2 O 3 is about 1 %. The corrosion potential of Ni60/1%La 2 O 3 composite coating is −0.697 V, which increase 0.057 V compared to −0.754 V of Ni60 coating, and the self-corrosion current density is reduced to 2.776 × 10−6 A/cm2 that is 0.053 times of 5.235 × 10−5 A/cm2 of Ni60 coating, which shows that the addition of 1 %La 2 O 3 effectively improves the corrosion resistance of the coating. • The directional structure coatings of Ni60 and Ni60/La2O3 were prepared, respectively. • La 2 O 3 resulted in the microstructural evolution of directional structure Ni60 coating. • Moderate amount of La 2 O 3 can promote the growth of uniform and dense passivation film. • The corrosion resistance of coatings can be improved by controlling the addition of La 2 O 3. [ABSTRACT FROM AUTHOR]

Achieving the stringent demands of sustainable tribological industrial applications poses a significant challenge, particular in optimizing the self-lubricant performance of nitride-based films. This paper tackled this challenge by designing and depositing a series of ZrN-MoSN composite films with varying (Mo + S)/Zr ratios, employing RF magnetron sputtering, aimed to enhance the tribological properties through utilizing the high loading capacity of the ZrN matrix and the exceptional self-lubricating attributes of Mo-S-N additives. After conducting thorough investigations on the microstructure, and tribological properties, the results revealed that the dense columnar structured ZrN-MoSN composite films displayed a polycrystalline composition comprising fcc-ZrN and hcp-MoS 2 phases, intertwined with amorphous phases of Mo(SN) x and MoS 2 (N 2). (Mo + S)/Zr ratios below 1.08 exhibited a minor impact on the room temperature (RT) tribological properties, while higher ratios led to degradation on RT average friction coefficient (COF) and wear rate (WR). However, the synergistic effect of ZrN matrix and the tribo-phases of layered MoO 3 and hard ZrO 2 contributed to the significant enhanced 500 °C tribological properties, particularly with an optimized (Mo + S)/Zr ratio of 0.43. [Display omitted] • ZrN-MoSN composite films were fabricated by the magnetron co-sputtering technique. • The films exhibited a coexistence of fcc-ZrN, hcp-MoS 2 , Mo(SN) x and MoS 2 (N 2) phases. • Incorporating Mo-S-N in ZrN notably bolstered the 500 °C tribological properties. [ABSTRACT FROM AUTHOR]

Laser direct energy deposition (LDED) is a repair and remanufacturing technology that has shown great potential, which is of significant importance for extending the lifespan of brake discs through repair and remanufacturing. This paper investigates the impact of Mn on the microstructure and micro-shear properties of Stellite 21 alloy coatings using methods such as EDS, XRD, SEM, EBSD, TEM, and micro-shear equipment, and process research. The research results indicate that the dilution rate increases with the increase in laser power, but changes insignificantly with variations in scanning speed. The optimal LDED parameters were as follows: laser power of 4400 W, scanning speed of 19 mm/s, and powder feeding rate of 25 g/min. The Mn addition prevented the continuous growth of columnar crystals in the Stellite 21 alloy coating, gradually presenting a polygonal grain characteristic. The M 23 C 6 and M 7 C 3 carbides precipitate as small particles at grain boundaries. With the addition of Mn, lattice distortion occurs, resulting in abundant dislocations in the coating and a transformation of γ-Co to ε-Co. The polygonal grain boundaries and carbides at the grain boundaries effectively hinder the movement of dislocations, thereby increasing the shear strength of the coating. The 5 % coating exhibits the highest shear strength and indentation rate, with values reaching 563 ± 16 MPa and 31.2 ± 1.8 %, respectively, and the shear curve is the most ideal. The grain boundaries of the polygonal grain structure also promoted slip at the grain boundaries, enhancing the plasticity of the coating with Mn addition. • Studied Laser energy direct deposition parameters for single-track forming. • Explored Mn's impact on coating shear strength in high-speed train brake discs. • Unveiled Mn's mechanism on Stellite 21 alloy coating shear strength. [ABSTRACT FROM AUTHOR]

Efficiently reducing friction and wear in an environmentally friendly lubrication manner remains a challenging endeavor. Here, carbon-based tribofilms with excellent friction-reducing and anti-wear abilities was in-situ formed from the poly-α-olefin oil (PAO6) on the friction interfaces of MoN-Ag composite films. A series of MoN-Ag films were prepared by multi-target magnetron sputtering process. Then, X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Raman, and Fourier-transform infrared (FTIR) spectroscopy, etc. were employed to investigate the microstructures, surface morphologies, mechanical properties of the MoN-Ag films, as well as the tribological performance under the luberication of PAO6 oil. The results showed that the MoN-Ag film consists of γ-Mo 2 N and c-Ag. With the increase of Ag content, the surface roughness of the films stays increased, while the hardness and elastic modulus of the films initially increase and then decrease. When the content of Ag is 2.7 at.%, the film had the highest hardness (24.1 GPa) and elastic modulus (316.5 GPa), and the MoN-Ag/oil solid-liquid system exhibited the lowest average friction coefficient of 0.087 and the lowest wear rate of 5.8 × 10−7mm3N−1 m−1 after a long duration. The catalytic effect of Ag facilitated the degradation of PAO6 molecules on the friction interface, resulting in the in-situ reorganization and formation of amorphous carbon-based tribofilms with graphite-like structures. In this paper, PVD technology was utilized to introduce Nano-Ag into MoN comosite films, preparing in a series of MoN-Ag composite films with varying Ag content. Then, the influences of Ag content on the microstructure, surface morphology, mechanical properties of the MoN-Ag films, as well as the tribological performance of these films in base oil, were investigated systematically. The catalytic effect of Ag in the solid-liquid lubrication system and the structure-activity relationship regarding the formation of carbon-based lubricating films from lubricating oil degradation were unequivocally determined. Furthermore, the study delved into the characterization and formation mechanism of in-situ generated lubricating carbon films at the friction interface, revealing the anti-friction and wear mechanisms of the solid-liquid lubrication system. [Display omitted] • The MoN-Ag film had the best mechanical properties at Ag content is 2.7 at.%. • The excellent tribological behavior under base oil was achieved catalyzed by Ag. • Carbon-based tribofilms was in-situ formed on the friction interfaces of MoN-Ag films. • A long-term, stable TMN/PAO solid-liquid lubrication system is constructed under room temperature. [ABSTRACT FROM AUTHOR]

In this paper, Fe-0.5C-15Cr wear and corrosion resistant alloy coating was prepared on 3Cr13 stainless steel surface by ultrasonic vibration assisted laser cladding technology. The effects of ultrasonic vibration frequency on the microstructure, microhardness and corrosion resistance of the coating were studied. The results show that the length of the dendrites of the cladding layer decreased significantly after ultrasonic vibration is applied, the grains size is refined significantly, and the morphology of the grain boundary carbides changed from fishbone-like to short rods, when the vibration frequency is 20.2 kHz, the grain refinement is the most significant, and the orientation of the dendrites is obviously weakened. The hardness of the applied ultrasonic vibration specimens increased by 10–20 HV 0.2 relative to the non-ultrasonic specimens, with the increase of vibration frequency, the hardness of the cladding layer firstly increased and then slightly decreased, and the peak appeared at 20.2 kHz. The coefficient of friction of the specimens when the ultrasonic frequency of 20.2 kHz is applied is lower than that of the specimens with non-ultrasonic frequency by 12.8 %, and the abrasive wear rate is reduced by 14.3 %. After ultrasonic vibration, the pitting potential of the cladding layer increases, the dimensional passivation current density decreased, the width of the passivation zone becomes wider, and the intergranular corrosion reactivation rate decreased, When the ultrasonic frequency is 20.2 kHz and 20.4 kHz, the pitting corrosion resistance and intergranular corrosion resistance of the cladding layer are significantly improved. This is because the cavitation effect, resonance effect and acoustic flow effect of ultrasonic vibration promote the non-uniform nucleation, refine the dendrites and intergranular carbides, and promote the redistribution of the corrosion-resistant element Cr in the in-grain martensite and grain boundary carbides, increasing the content of Cr in the matrix, and thus improving the wear resistance and corrosion resistance of the cladding layer. [ABSTRACT FROM AUTHOR]

In the production of polysilicon, valve sealing surfaces are vulnerable to issues such as erosion wear from silicon powder, corrosion from chloride ions, and leakage leading to functional failure. This paper proposes a process route for laser cladding rare earth La 2 O 3 doped Ni-based WC coatings on the surface of AISI 304 steel, and carries out a study on the macroscopic morphology, microstructure, physical phase evolution pattern, wear resistance and corrosion resistance of WC-Ni60 composite coatings from different particle sizes of rare earth La 2 O 3. The results show that the addition of rare earth La 2 O 3 optimized the macroscopic morphology and microstructure of WC-Ni60 coatings, and improved the wear and corrosion resistance of the coatings. Among them, micron-La 2 O 3 showed the most significant improvement in the performance of WC-Ni60 coatings, with wear and self-corrosion current density reduced by 71.43 % and 59.63 %, respectively, compared with the substrate. • Effect of La 2 O 3 particle size on laser cladding WC-Ni60 coatings was investigated. • La 2 O 3 improves the macro-morphology and microstructure of the coating. • Micron-La 2 O 3 is better than nano-La 2 O 3 for fine grain strengthening of the coating. • Effect of micron-La 2 O 3 on morphology, structure and properties of the coating is more significant. [ABSTRACT FROM AUTHOR]

It is challenging to obtain the underwater wet laser cladding layer with excellent properties while maintaining formability. In this paper, the method of using synchronous mechanical vibration assisted in the underwater wet laser cladding process of TiN/Fe-based cladding layer was introduced. The effect of mechanical vibration frequency on the dilution rate, microstructure, corrosion resistance, tribo-corrosion behavior of the cladding layer was studied. The result displayed that with increase of mechanical vibration frequency, the dilution effect of the substrate was obviously weakened and the phase changed from ferrite to ferrite and austenite, and TiN particles were evenly distributed. In addition, the grain size of the cladding layer showed a tendency to decrease first and then increase. When the mechanical vibration frequency was 400 Hz, the grain refinement phenomenon was the most obvious and the average grain size was 8.39 μm. Based on the effect of dispersion strengthening and fine grain strengthening, the microhardness and wear resistance of the cladding layer assisted at 400 Hz were improved, and the wear rate was 1.17 × 10−15m3N−1 m−1. While the cladding layer assisted at 400 Hz exhibited better corrosion resistance by forming a dense passivation film. In addition, the mechanism of mechanical vibration on microstructure evolution and performance enhancement of the cladding layer was also analyzed. This study provided the theoretical support for the formability of the underwater laser wet cladding assisted by mechanical vibration. • The TiN/Fe-based underwater wet cladding layer was successfully prepared assisted with mechanical vibration. • Action mechanism of mechanical vibration on TiN/Fe-based underwater wet cladding layer is explained. • The grain refinement mechanism of TiN/Fe-based underwater wet cladding layer is proposed. • Dispersion strengthening and grain refining strengthening are the main strengthening mechanisms. [ABSTRACT FROM AUTHOR]