The Ni60 alloy coating was prepared on the 45 steel substrate by supersonic plasma spraying. Under the condition of high frequency induction remelting + forced cooling, the effects of surface heat dissipation conditions on the microstructure, element distribution and properties of the coating were studied. It is shown that in the natural heat dissipation condition, the coating forms a directional dendritic structure, and the surface layer is protected by the surface coating to change the surface heat dissipation condition, so that the coating structure transforms to the equiaxed crystal with the sintering characteristics, and two obvious In different regions of the tissue, the tissue is small and compact, but the tissue and elements are unevenly distributed in the vicinity of the substrate. The tissue grows close to the surface of the coating, but the uniformity of elements and tissues is significantly improved. Compared with the uncovered layer. The coating, the coating element and the matrix element of the
In order to study the effect of 0.76% Y element on the structure, high temperature oxidation behavior and tribological properties of AlTiN coating, AlTiN and AlTiYN coatings were deposited on the surface of cemented carbide (YG3X) by multi-arc ion plating. The microstructure of the coating was studied by electron microscopy (SEM) and X-ray diffractometry (XRD). The mechanical properties of the coating were characterized by nanoindentation and scratch tester. The high temperature oxidation resistance of the coating was analyzed by high temperature oxidation test. The test machine studied the friction and wear behavior of the coating. The results show that after adding Y element, the AlTiYN coating has grain refinement, densification of microstructure, hardness and toughness increase, and the bonding strength is significantly improved. AlTiN coating passes 900 °C / 2 h After oxidation treatment, it was completely oxidized; while the A1TiYN coating was not completely oxidized after 900 °C/2h oxidation treatment,
Supersonic laser deposition technology is a new material deposition technology that combines laser heating and cold spraying. The Ti6Al4V coating is prepared on medium carbon steel substrate by supersonic laser deposition technology, and SEM, XRD and electrochemical corrosion tests are used. The coating thickness, microstructure, phase composition and corrosion resistance were characterized. The results showed that the coating deposition efficiency, compactness and coating were within a certain range of laser irradiation temperature (ie, deposition temperature). The bonding strength between the layer and the substrate increases with the increase of the laser irradiation temperature. When the laser irradiation temperature is 800 °C, the deposition efficiency is 4 times that of the cold spraying, and the porosity in the coating is only 4.38%. The bond strength of the coating to the substrate is 75 MPa. Due to the low heat input, the phase composition of the coating is basically the same as that of the original
Laser solid solution and aging with a rectangular laser beam of 25 mm×8 mm was performed on 17-4 PH precipitation-hardening stainless steel for surface strengthening to resolve pitting, water erosion and fracture of turbine blades.The treated samples were characterized by optical microscopy(OM), X-ray diffraction(XRD), SEM, EBSD, microhardness tester and tensile tester. Results show that the laser solid solution hardening layer has obvious diffraction peaks of ε-Cu and retained austenite compared with the traditional solid solution. The rapid heating and cooling of laser solid solution has a positive effect on the formation of high density dislocation and vacancy. The interactions between the precipitated second phase particles, such as ε-Cu and Nb C, with the high density of dislocations increase the energy of dislocation movement. The thickness of the hardening layer is about 3.5 mm(HV400), and a hardness gradient of 130~140 HV exists in hardening layer,while the highest hardness is 500 HV on the surface. T
Fluorescent agent can be used to monitor the initial stage of aluminum alloy corrosion. Effects of species and concentration of fluorescent agents in protective coatings of aluminum alloy on the corrosion monitoring sensitivity were studied. Fluorescence responses of 8-hydroxyquinoline, morin and coumarin to Al3+ and pH were studied by fluorescence spectra. The influence of fluorescent agent addition on the corrosion monitoring sensitivity and performance of the coatings was characterized by fourier transform infrared spectroscopy(FTIR), SEM, fluorescence microscope and electrochemical impedance spectroscopy(EIS). Results show that 8-hydroxyquinoline has obvious fluorescence response to the change of Al3+concentration. Coumarin is sensitive to the change of pH values. The addition of 8-hydroxyquinoline or coumarin does not obviously affect the sol solutions and sol-gel films. Additionally, the sol solutions keep stable, and the films are dense with good adhesion to the matrix. The addition of fluorescent agen
To enhance the service-life of the variable transmission’s cone disc, a type of commonly used material, 38 CrMoAl steel, was selected as the testing material. Plasma nitriding with lower ratio of N2 to H2 at different temperature was used for surface modification. The treated samples were characterized by optical microscopy（OM）, X-ray diffraction（XRD）,microhardness tester and wear tester. The results show that no white layer is formed by plasma nitriding at 520 ℃,N2∶H2=1∶4 and 540 ℃, N2∶H2=1∶5, and the XRD confirmes that there exists no γ′-Fe4 N phase in the surface layer, which means that only nitriding diffusion layer can be formed by changing the temperature and the nitrogen hydrogen ratio.Meanwhile, it is found that the brittleness of the nitriding layer is decreased and the toughness is improved comparing with those in conventional plasma nitriding. Therefore, the research can be taken as important guidelines in surface modification for variable transmission’s cone disc.
The hot-pressed and sintered ball-milled Ti2AlC submicron powder was used as a raw material, agglomerated into micron-sized powder by hydrothermal treatment, and Ti2AlC coating was deposited on Zr-4 alloy substrate by cold spray technique. Scanning electron microscope and metallography were used. The microstructure of Ti2AlC particles and coatings were characterized by microscope, XRD diffractometer and laser particle size analyzer. The basic mechanical properties of Ti2AlC coatings were tested by microhardness tester and tensile test system. Coatings were measured by N2 adsorption method. The pores were measured by electrochemical workstations. The results show that the addition of ammonium sulfate can promote the agglomeration of submicron particles when the Ti2AlC powder with average particle size <0.3 μm is hydrothermally treated. The average particle size of the agglomerated powder can reach 6 Μm. This powder has the best cold spray characteristics. The deposited Ti2AlC coating has a thickness of 100 μm.
Aim at the complex and costly preparation of the superhydrophobic surfaces, a magnetic regulation method was proposed by a straightforward process. Based on the chaining of magnetic particles, the magnetorheological elastomer film(MREF) was fabricated to form rough micro-structures and tunable hydrophobicity under the magnetic field. Consisting of polydimethylsiloxane and dispersive carbonyl iron particles, the MREF was characterized using scanning electronic microscopy(SEM) and contact angle instrument. The result show that the micrometer-sized mountainous protrusions are randomly distributed at the surface of MREF, the contact angle increases from 110° to 158.2°, with different magnetic intensity in the preparation, which designates a status of superhydrophobicity. Further investigations show that film thickness,particle size and weight ratio are significant to the tunabillity of hydrophobicity for the prepared MREF surfaces.
In view of the pit defect caused by the nickel plating of the aluminum alloy disc substrate, resulting in substrate scrap, the microstructure defects of the aluminum alloy disc substrate were studied by scanning electron microscope(SEM)and focused ion beam microscope(FIB). The influence of the pretreatment process on the surface morphology, phase distribution and surface wettability of aluminum alloy surface were analyzed through the simulation of electroless nickel plating pretreatment process. The result show that the aluminum matrix around the intermetallic compounds dissolves during the pretreatment, causing the precipitated phase(intermetallic compounds) to fall off and forming micro-pits. When the micropit is of deep size, it is difficult for the gas to discharge in time. Then the pit is difficult to immerse by plating solution,resulting in less Zn coverage at the inner surface of the micro-pit. During the nickel plating process, the gas in some deep micro-pits cannot be all eliminated in time when the
The latest research progress is reviewed from the basic principle of micro-arc oxidation technology, functional ceramic coating design preparation and service performance. The growth process and formation mechanism of micro-arc oxidation coating are introduced. The key process parameters (electrolyte composition, Influence of electrical parameters) and metal matrix composition on coating growth and film-based bond strength; based on anti-wear, anti-corrosion, thermal protection, thermal control, dielectric insulation, catalysis, biological and other special functional requirements, Layer composition/structural design, and how to control the process/composition/structure to obtain high-performance functional coatings. Finally, the challenges of micro-arc oxidation technology are pointed out, and the basic theory, coating process and engineering application are prospected. Future development direction.
In order to study the influence of film fragments on the friction and wear properties of tungsten doped diamond-like carbon films(W-DLC films) under boundary lubrication conditions, the W-DLC films were fabricated on the surface of M50 high temperature bearing steel and(100) crystal Si, respectively. The pure W-DLC film, obtained by etching the substrate Si,was mashed into its fragments. Raman spectroscopy and SEM were used to study the structure of the films and its fragments.Friction and wear properties of the film were tested by friction and wear tester and 3 D white light interferometer. The results show that the average friction coefficient of the friction system increases by 2%, 4% and 10%, when the load is 2, 5 and 10 N,respectively. The average friction coefficient of the friction system decreases from 0.1277 to 0.1131, and then to 0.1031, when the load is increased from 2 N to 5 N and 10 N. Additionally, the wear width, depth and volume of the film increase by the coupling of the load and the film fr
The W2N and WSiN coatings were prepared by reactive magnetron sputtering. The microstructure of the coating was studied by XRD, SEM and AFM. The mechanical properties of the coating were tested by nanoindenter. The friction and wear of the coating was characterized by friction and wear meter. Behavior. The results show that the atomic fraction of 2.4% Si doping does not cause significant changes in the phase structure and mechanical properties of the W2N coating, but reduces the surface roughness of the coating (from 10.56 nm to 8.35 nm). Stainless steel substrate, W2N coating The friction coefficients of the layer, WSiN coating and Al2O3 dual sphere are 0.62, 0.42 and 0.35, respectively, and the corresponding wear rates are 4.2×10-14, 3.8×10-16 and 3×10-16 m3/N·m. The frictional factors of the base, W2N coating, WSiN coating and GCr15 dual sphere are 0.56, 0.47 and 0.49, respectively, and the corresponding wear rates are 5.9-10-15, 2.8×10-16 and 3.2×10-16 m3/N, respectively. · m. In the case of the above two
It is of great significance to study the surface wettability of cemented carbide tools for the improvement of tool life and processing surface quality. Micro-pits arrays on the YG3 surface were fabricated by nanosecond pulsed laser with a wavelength of 1064 nm. The optical microscope, optical profiler and contact angle measurement were used to measure the surface morphology and contact angle. The influence of surface morphology on contact angle under different laser average power, scanning times and micro-pits spacing were investigated. Based on Wenzel's theory, the geometrical morphology model of micro-pits was established to analyze the influence mechanism of surface morphology on contact angle. Results show that the diameter and depth of micro-pits increase as the laser average power or scanning times increase. The micro-pits distribution density increases with decreasing micro-pits spacing. Under three conditions, all the surface roughness ratios increase. The cosine contact angle is positively related to
Laser cladding techniques applied in the preparation of liquid nitrogen S355 auxiliary cooling surface of the Al-based amorphous steel marine coatings, the use of SEM, XRD, electrochemical workstation interface morphologies technical analysis table cOATINGS The phase composition was studied. The effect of liquid nitrogen assisted cooling on the properties of the coating and the corrosion performance of the coating after immersion for 10, 20, 40 and 80 days in 5% NaCl solution were studied. The results showed that it was coated with liquid nitrogen assisted cooling. There is a small amount of amorphous AlFeNi phase in the layer; the coating forms a good metallurgical bond with the matrix; the surface structure is fine, the TiC is uniformly dispersed, and the crack pores are less. The microhardness of the coating surface is increased by 15%; residual stress It is basically flat with natural cooling and is tensile stress; its corrosion resistance has also been significantly improved.
To study the codeposition behavior of Ni-Co-ZrO2 composite coatings in the initial stage of electro crystallization,cathodic voltammetry and chronoamperometry test methods were used in an acidic amino sulfonate system, and the nucleation mechanism of Ni-Co-ZrO2 composite coating was revealed by calculating electrochemical kinetic parameters. The results show that the presence of nano particles in the bath resultes in a positive shift of Ni-Co reduction potential and reduces the cathodic polarization. The nucleation and growth process for Ni-Co alloy and Ni-Co-ZrO2 composite coatings is closer to the Scharifker-Hill instantaneous nucleation model with diffusion controlled mechanism. The nucleation relaxation time of Ni-CoZrO2 composite coating becomes shorter at low potentials, the nucleation rate becomes higher, and the addition of ZrO2 nanoparticles in bath promotes the nucleation and growth of the matrix metal. The peak current of the composite system at high potential is slightly lower than that of the all
For the hydrochloric acid-sulfuric acid system, the electrochemical corrosion of aluminum foil was carried out by coupling external magnetic field, and the effects of magnetic eddy current effect (MHD effect) on the electrochemical behavior, interface behavior and mass transfer of aluminum foil were systematically studied. X-ray diffraction was used. XRD), low temperature nitrogen adsorption, scanning electron microscopy (SEM) and other methods were used to characterize the corrosion foil samples. At the same time, the electrochemical properties of aluminum foil were studied by chronopotentiometry, polarization curve, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the MHD effect can inhibit the growth of oxide film, increase the adsorption amount of Cl- on the surface of aluminum foil, reduce the thickness of the diffusion layer, strengthen the mass transfer of Cl-/Al3+ into the pore/hole, and reduce the ion in the electrolyte. Through the introduction of the magnetic fie