Q235 Substrate Research Articles

Experimental and numerical investigations on cold-formed titanium-clad bimetallic steel angle and channel section stub columns

Titanium-clad bimetallic steel (TCBS) exhibits outstanding corrosion resistance, and can be advantageously applied in corrosive environments. This study investigated an innovative application of TCBS in cold-formed stub columns. During the cold-forming process, TCBS demonstrated no discernible separation at the bonding interface of the Q235 substrate layer and TA1 cladding layer, indicating the maintenance of synergistic deformation between the cladding and substrate layers. The compressive behavior and ultimate resistance of cold-formed TCBS angle and channel section stub columns were investigated using both experimental and numerical methods. These tests included material tensile flat and corner coupon tests, initial local geometric imperfection measurements, and stub column tests. The stub column test comprised four cold-formed TCBS angle section stub columns and three cold-formed TCBS channel section stub columns covering the non-slender and slender cross-sections. The experimental results were utilized to validate the finite-element (FE) model, which was then used in a parametric study to obtain further numerical data at different cross-sections. A comparative analysis of the ultimate resistance from the tests and numerical analyses with the predicted results from design approaches in EN 1993-1-1, AISI S100, and the direct strength method (DSM) was revealed. The evaluation findings generally showed that the EN 1993-1-1 design method forecasts for cold-formed TCBS channel section stub columns were dangerous. The non-slender cross-section classification coefficient, which was inapplicable to cold-formed TCBS channel steel stub columns, was the primary cause of the above unsafe prediction. As for the design approaches in AISI S100 and DSM for cold-formed TCBS angle and channel section stub columns, as well as those in EN 1993-1-1 for cold-formed TCBS angle section stub columns, they were judged safe but conservative. The above prediction error was mainly caused by ignoring the enhancement in strength properties of the TCBS after the cold-forming process. The considerations mentioned above led to the proposal and demonstration of modifying recommendations that offered safe, accurate, and consistent design approaches to ultimate resistance for the cold-formed TCBS angle and channel section stub columns.

Fabrication and characterization of self-lubricating anti-wear 316L stainless steel/h-BN composite coatings on Q235 substrate via laser cladding

This paper presents the fabrication and characterization of self-lubricating, anti-wear 316L stainless steel composite coatings on a Q235 substrate using 316L stainless steel powders and nanoscale hexagonal boron nitride (h-BN) ceramic particles via coaxial powder feeding laser cladding. The influence of process parameters on cladding quality and geometry, and the impact of h-BN contents (2 wt% and 5 wt%) on the microstructure and mechanical properties of the coatings were studied. Optimal process parameters for 316L/5wt%BN coatings were identified: a powder feeding rate of 3–4 rpm, a laser power of 2200–2400 W, a scanning speed of 4–5 mm/s, and an overlapping rate of 40 %. Microstructural analysis showed a smooth surface without cracks or pores. X-ray diffraction revealed intermetallic compounds such as CrB, Cr2N, Fe3N, BN, and γ-(Fe, Ni). The inclusion of h-BN nanoparticles enhanced grain refinement, significantly increasing microhardness. Coatings with 5 wt% h-BN achieved an average microhardness of 438.8 HV10, 2.5 times higher than the substrate and the 316L stainless steel. Additionally, h-BN reduced friction coefficients, leading to substantial wear reduction. The 316L/5 wt% h-BN sample experienced only 4.2 mg of wear, 45.16 % of the substrate’s wear. These findings highlight the beneficial effects of h-BN nanoparticles on 316L stainless steel coatings, enhancing wear resistance, hardness, and overall performance.

Investigation on corrosion resistance of electroless Ni-W-P coatings co-deposited with SiO2 nanoparticles

The corrosion of materials in sea environment are generally caused by salt spray, tidal action and adhesion of marine organisms. It is necessary to ensure the materials possess the required strength and good corrosion resistance during operation. Although the existing Ni-W-P electroless plating can provide a certain degree of corrosion protection, its corrosion resistance is still limited under harsh marine condition. SiO2 nanoparticles have received extensive concern due to their excellent corrosion resistance, which has been considered as potential candidates for enhancing corrosion resistance in multicomponent electroless coatings. In this study, the electroless Ni-W-P coatings with SiO2 nanoparticles co-deposition on the Q235 substrate was prepared. The coating was characterized through scanning electron microscopy (SEM), x-ray diffraction (XRD), polarization techniques, and electrochemical impedance spectroscopy (EIS). As a result, the Ni-W-P coating co-deposited with SiO2 nanoparticles demonstrates superior corrosion resistance compared to the pure Ni-W-P coating. The surface of SiO2 nanoparticles contain three distinct bonded hydroxyl functional groups, which can influence the ionic reaction in the plating solution and the deposition of elements in the coating. After modified by PVA, it can be uniformly dispersed in the coating, and the composite coating with SiO2 nanoparticles co-deposited is transformed into a nanocrystalline structure. The even distribution of SiO2 nanoparticles fill the defects within the coating, leading to a reduction in porosity, permeability, and susceptibility to penetration of corrosive media. Concurrently, the nanoparticles facilitate surface passivation, forming a stable interface with substrate and coating that inhibits electrochemical reactions and diminishes the rate of self-corrosion reactions. The good and stable corrosion resistance is achieved at the SiO2 concentration of 9 g l−1 and PVA concentration of 1.08 g l−1. These findings offer valuable insights for addressing corrosion challenges in the field of marine engineering.

Mechanism Insights in Anticorrosion Performance of Waterborne Epoxy Coatings Reinforced by PEI-Functionalized Boron Nitride Nanosheets.

Functionalized hexagonal boron nitride nanosheets (BNNSs) have arisen as compelling anticorrosive additives, yet the precise mechanism of their corrosion resistance enhancement in coatings remains unclear. Here, polyethylenimine functionalized BNNSs (PEI-BNNSs) with approximately 6-11 layers were prepared through a "one-step" method. Then, the PEI-BNNSs/Waterborne epoxy (WEP) composite coatings were incorporated via the waterborne latex blending method for the anticorrosion of the Q235 substrate. The impedance modulus (|Z|f = 0.01 Hz) of 0.5 wt % PEI-BNNSs/WEP composite coating soaked in 3.5 wt % NaCl solution for 35 days increased by 4 orders of magnitude compared to pure WEP coating, exhibiting exceptional long-term resistance against corrosion. The positron annihilation lifetime spectroscopy and corrosion product analysis demonstrated that the reinforced anticorrosion capabilities are not solely ascribed to the "tortuous path effect" arising from BNNSs impermeability. These mechanisms also encompass the reduction in free volume fraction and radius of the free volume cavities within the composite coating brought about by the PEI molecules. Additionally, the increase in coating adhesion, promoted by PEI, plays an important role in augmenting the barrier properties against corrosive agents. This study provided a full comprehension of the role played by functionalized BNNSs in fortifying the anticorrosion attributes of WEP coatings.

Study on the Corrosion Resistance Of Thermal Sprayed Aerospace Coatings Under The Action Of High Current Pulsed Electron Beam

Aluminum-based amorphous alloys have excellent mechanical properties and corrosion resistance and are currently used in the form of coating materials for the protection of aircraft surfaces. In this study, AlCoCe alloy and powder are prepared, and then AlCoCe alloy coating is prepared on Q235 substrate by supersonic flame thermal spraying technology, and finally, the surface remelting modification treatment is carried out on the coating by current pulsed electron beam, and the transformation behavior of microstructure of the coating and the change of the corrosion resistance in this process are analyzed by structural characterization and corrosion experiment, to make clear the relationship between the structure of the coating and its corrosion resistance performance. After 15 current pulsed electron beam pulses, the coating surface formed a layer of dense and homogeneous composition of the amorphous structure of the treatment layer, when the number of pulses is higher, due to the heat of the substrate leads to a decrease in the cooling rate, which in turn will lead to the emergence of a crystalline structure of the surface treatment layer.

Corrosion Performance of Epoxy/Sulfur–Selenium Coating on Q235 Steel

Sulfur powder (99.99%) and selenium powder (99.99%) were mixed and heated to approximately 300 °C to obtain an S-Se alloy. It has good flowability at 130 °C and can be applied to Q235 steel to obtain a S-Se coating. Epoxy was used as a filler, and the S-Se alloy was applied as a coating. This combination was utilized to create the composite coatings of epoxy/sulfur–selenium (E/S-Se). To investigate the corrosion resistance of this coating on Q235 steel substrate, we conducted measurements and obtained electrochemical impedance spectra (EIS) and linear polarization curves (LPC). These measurements were performed in a three-electrode cell within an electrochemical workstation using a 3.5 wt.% NaCl aqueous solution. By comparing bare Q235 steel, S-Se, and E/S-Se, the study found that the E/S-Se coating had a higher self-corrosion potential (−0.484 V vs. SCE) and the lowest self-corrosion current density (2.361 × 10−11 A/cm2). The purpose was to simulate the corrosive environment experienced by condensate return pipe walls in petroleum refining equipment. Additionally, experiments were carried out using 0.01 mol/L HCl solution as the corrosion medium at different temperatures (40 °C, 60 °C, 80 °C). The results indicated that the E/S-Se coating exhibited a lower corrosion rate compared to the Q235 steel substrate. Under immersion conditions at 40 °C and 60 °C, no corrosive substances were detected on the surface of the coating. The test results demonstrated that the E/S-Se coating exhibited superior corrosion resistance compared to the Q235 substrate, providing up to 99% protection for the substrate.

Optimization on laser cladding parameters for preparing Ni60 coating along with its friction and wear properties

Ni60 coating was prepared on Q235 substrate by using laser cladding method, and the optimization of processing parameters was performed based on response surface methodology. Laser power, scanning speed and powder feeding rate were considered as input variables, while dilution ratio, ratio of width to height, and hardness were considered as output responses. Then, the influence of processing parameters on cladding quality was studied by single track cladding experiments, and the optimal parameters were obtained by regression analysis. Subsequently, Ni60 coating was successfully prepared and its friction and wear properties were investigated. Results show that the optimal parameters are: laser power 540 W, scanning speed 30 mm/s, powder feeding rate 0.2 r/min and overlapping step 0.4 mm. The microhardness of coating is 499.4 HV0.5, which is 5 times higher than that of the substrate. Correspondingly, the wear loss of the coating is 68.3% and 82.1% lower than that of Q235 substrate at room temperature and 400 °C respectively, indicating that the Ni60 coating can improve the wear resistance of Q235 steel significantly.

Effect of Different Contents of WC on Microstructure and Properties of NiCrMo Coatings Prepared by PTA

During the service process of the mechanized fishing boat, its low carbon steel hull and parts are extremely susceptible to Cl− erosion and seawater scouring, which cause a decrease in strength and lead to failure. To increase its service life and reduce maintenance costs, coating protection technology is widely used. In order to solve the problem of poor adhesion between paint coating and substrate and low strength of metal coating, NiCrMo-WC coatings with different WC contents (0 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%) were prepared on the surface of Q235 substrate by plasma cladding technology. The coatings were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy spectrum analysis (EDS), etc. Its phase formation rule, microstructure and element distribution were studied. Microhardness test and electrochemical corrosion test were carried out. The study found that the 20 WC coating has the highest average hardness (563.1 HV). It is about 3.25 times of the Q235 substrate. It has the lowest friction, wear rate and lower friction coefficient, showing the best wear resistance. The 15 WC coating has the lowest self-corrosion current density (3.4934 × 10−7 A/cm2) and the lowest corrosion rate (0.0041 mm/a), which is only 3.7% of the corrosion rate of Q235 steel.

Research on in situ laser cladding of 304 stainless steel coating on Q235 substrate in underwater environment

In this research, 304 stainless steel coating was prepared on the surface of Q235 steel by in situ laser cladding technology in both underwater and in-air environments. The optimal process parameters of laser cladding in the underwater environment were first investigated by using a homemade local dry laser torch. The effects of the laser power, scanning speed, and wire feed speed on macroscopic forming, geometric characteristics, and the microstructure of the cladding layers were investigated. Under the optimal process parameters, the effects of the water environment on macroscopic forming, geometric characteristics, and the microstructure and microhardness of the cladding layers were studied. The results showed that as the environment transferred from underwater to air, the height (H) and cladding angle (α) of the deposited region (DR) decreased, but the fusion width (W) and the depth (h) of the fusion region (FR) increased due to the slow cooling rate and long residence time at high temperatures. For both underwater and in-air cladding layers, the microstructure of DR and FR was equiaxed dendrites and columnar dendrites. Besides, a cellular structure appeared in the FR of the underwater cladding layer. The width of the lathy δ ferrite in the FR in the underwater environment was smaller than that of the in-air environment. Finally, the grain size of the underwater specimen was finer, so the average microhardness value of the in-air specimen was lower than that of the underwater specimen.

All-organic superhydrophobic coating with anti-corrosion, anti-icing capabilities and prospective marine atmospheric salt-deliquesce self-coalesce protective mechanism

Water-repellent and interfacial non-wetting superhydrophobicity has great potential to address corrosion/icing-induced material-deterioration problems. Herein, an all-organic superhydrophobic coating was constructed using facile and substrate-independent spray-coating method based on PTFE and PDMS. FE-SEM, EDS, and XPS techniques were used to analyze the surface topographies and chemical compositions. The coating exhibits superior anti-fouling and self-cleaning properties against various liquid and solid contaminants due to the synergic effect of low surface energy and hierarchical structures. The EIS and potentiodynamic polarization results show improved charge transfer resistance (Rct), positive shifted corrosion potential (Ecorr), and decreased corrosion current density (Icorr), implying significantly enhanced anti-corrosion performance with 99.83 % inhibition efficiency. Besides, the delay rate of ice-freezing time of the coating is 232 % at −5°C, 137 % at −10 °C and 204 % at −15 °C compared with uncoated Q235 substrate respectively. The ice adhesion strength of the coating accounts for only 6.55 % at −5°C, 7.03 % at −10 °C and 9.35 % at −15 °C than that of the bare Q235 carbon steel, demonstrating ultra-low ice adhesion force and anti-icing capabilities. The hygroscopic and deliquesce behaviors of NaCl salt particles reveal an intriguing salt-deliquescence self-coalescence phenomenon and prospective anti-corrosion mechanism for superhydrophobic materials in high-humidity marine atmospheric environments.

Improvement of Microstructure and Properties of Q235 Steel by Iron-Based Laser Cladding Coating

Laser cladding is a repair and surface-strengthening technology for the protection of metal parts. It is an effective method for improving the properties of various metal substrates. The process involves melting and solidifying alloy powder on the surface of the substrate. The aim of the present study was to explore the effect of iron-based alloy laser cladding coating on Q235 substrate. Three types of specimens were obtained from Q235 base material using a 5 kW cross-flow CO2 laser beam. Sample 1 and sample 2 were obtained by the addition of rosin to the iron-based alloy powder. Sample 3 was obtained through the addition of rosin and vanadium to the iron-based alloy powder. A gas curtain was used to wrap the molten pool of samples 2 and 3. The surface hardness of the specimens was determined using a Rockwell hardness tester, and the tensile strength was evaluated using the universal mechanical testing machine. The microstructure of the cladding coating was explored using an Olympus optical microscope and SEM. The results showed that the average hardness of sample 2 and sample 3 was 6.42% and 19.84% higher than that of sample 1. The average tensile strength of samples 2 and 3 was 7.42% and 10.37% higher than that of sample 1. The grain of sample 3 was finer than that of sample 2, and that of sample 2 was finer than that of sample 1 under the same magnification. Rosin minimized oxidation of the substrate, whereas the gas curtain prevented the entry of air into the molten pool, hence the improved properties of samples 2 and 3 compared with that of sample 1. Rosin and the gas curtain protected the powder from oxidation loss and improved the quality of the cladding coating. The results of the present study show that rosin reduced the oxidation of iron-based powder, whereas vanadium improved the hardness and strength of the substrate as well as refined the grain size.

Effect of Fe content on microstructure and corrosion resistance of Ni-based alloy formed by laser cladding

Fe content has a dramatic effect on the properties of laser cladding Ni60 coatings, but there is a lack of in-depth research at present. In this article, Ni60 coatings with different Fe content were prepared on Q235 substrate by laser cladding technology. The microstructure, phases, and electrochemical corrosion resistance were explored detailed. With the increase of Fe content, the phases of the coating changes from ellipsoidal γ-FCC+ massive chromium-rich phase + γ-FCC/(Ni3B + Ni3Si) ternary eutectics to γ-FCC/(Cr, Fe)7C3 eutectics. The massive hard phases in the coating almost disappeared and the distribution of Cr in the coating becomes more uniform. The corrosion resistance becomes worse at first and then improves significantly. When the Fe content reaches to 25 wt%, the coating exhibits excellent corrosion resistance almost comparable to that of Ni60AA, which provides a new path for the low-cost application of Ni60 series coatings at abrasive occasions.

Self‐repairing oil‐impregnated gel coatings based on reversible physical cross‐linking for anti‐fouling and anti‐corrosion

AbstractCorrosion and biofouling are the most severe threats to the security of engineering equipment and materials. Oil‐impregnated gel (OIG) is a promising coating material for both corrosion protection and biofouling prevention. Unfortunately, OIGs are prone to damage due to their weak mechanical strength, and most of the reported OIGs are irreversibly cross‐linked through covalent bonds. To meet the great demand of self‐repairable OIGs for their durable applications, we develop a self‐repairable OIG coating based on the reversible sol‐gel process of styrene‐isoprene‐styrene triblock copolymer (SIS) and n‐hexadecane in the current work. The rheological properties of SIS/hexadecane were investigated by a rotary rheometer, which revealed the reversible sol‐gel transition during the cooling process as well as the gelation temperature with the SIS concentration above 2%. Owing to the dynamic hexadecane liquid layer and low‐modulus gel surface, the coating displays outstanding sliding properties to various fluids as well as impressive repellence to bacteria. The water sliding angles on OIGs are below 5° as measured by a water contact angle system. Moreover, it can serve as a barrier against corrosion medium and can be in situ repaired by the laser irradiation based on photothermal effect once damaged. The electrochemical impedance spectroscopy indicated the impedance modulus at 0.01 Hz (|Z|0.01Hz) of the OIG coatings on Q235 substrate is 6.34 × 109 Ω cm2, and the repairing process was monitored by the scanning Kelvin probe microscope. This research proposes a novel strategy to prepare the self‐repairing coatings for anti‐adhesion and anti‐corrosion based on the physically cross‐linked oil‐impregnated gel.

Understanding interface evolution during explosive welding of silver foil and Q235 substrate through experimental observation coupled with simulation

In this work, explosive welding was introduced to manufacture Ag coating on Fe substrate. The microstructure evolutions of the Ag/Fe joint interface and the associated governing mechanisms during the collision process, were investigated by a comprehensive study combined advanced characterizations and smoothed particles hydrodynamics simulations. It was concluded that the self-developed explosive welding process enabled to attain high-quality Ag coatings effectively, certified by absence of geometric defects at the Ag/Fe interface and the surface of Ag foil. The simulation accurately reproduced the wavy interface and vortex structure observed in experiment. From this, the evolution of the wave was reconstructed and the formation mechanism of the vortex was revealed. The microstructure analyses revealed a remarkable diversity of the grain structure near the Ag/Fe interface. The equiaxed fine grains related to dynamic recrystallization were formed in the vicinity of the interface and also within the vortex. The grains of the Fe matrix slightly away from the interface became elongated, which reflected well the deformation features. Meanwhile, the columnar grains induced by molten and re-solidified processes were observed at the vortex boundary. The variation of these grain structures was responsible for the inhomogeneity of nanoindentation hardness distribution.

Effect of c-BN on the microstructure and high temperature wear resistance of laser cladded Ni-based composite coating

In this study, Ni-based Ni60 + Cu/h-BN + MoO3 and Ni60 + Cu/c-BN + MoO3 composite coatings were fabricated by laser cladding on a Q235 substrate. Compare with the addition of h-BN, the effect of c-BN on the microstructure, high temperature hardness and wear resistance properties of the coating from 25 °C to 800 °C were analyzed. The results show that part of c-BN is decomposed during laser cladding process, resulting in the formation of Cr(Mo)B, Cr5B3, CrN and MoN reinforcements. The periphery of the remaining c-BN particle is allotropic transformed to h-BN under laser irradiation. The content of the reinforcement in the coating is increased and the distribution is more uniform, therefore, the hardness of the coating is increased. This resulted in a reduction of the wear rate from 25 °C, 200 °C, 400 °C, 600 °C to 800 °C by 77%, 61%, 29%, 46% and 39%, respectively. The abrasive and adhesive wear are released because of the increasing of deformation resistance and interface strength of γ-(Ni, M) matrix and Cr(Mo)B. In the meantime, the formation of h-BN provides lubricating property over the wide temperature range.

Microstructure and corrosion properties of AlCrxNiCu0.5Mo (x = 0, 0.5, 1.0, 1.5, 2.0) high entropy alloy coatings on Q235 steel by electrospark – Computer numerical control deposition

The AlCrxNiCu0.5Mo (x = 0, 0.5, 1.0, 1.5, 2.0) HEAs were prepared via arc melting. The x = 0 HEA is composed of BCC1 + BCC2, while x = 0.5, 1.0, 1.5 and 2.0 HEAs are comprised of FCC + BCC2. With the increasement of x, their brittleness decreases, while their plasticity increases. The HEA coatings were deposited using the as-cast HEA electrodes via electrospark – computer numerical control deposition. All HEA coatings contain BCC solid solution. The electrochemical corrosion test in 3.5%NaCl solution and salt spray corrosion test show that the produced HEA coatings can obviously improve the corrosion resistance of Q235 substrate.

Synergistic effect of carbide and amorphous phase on mechanical property and corrosion resistance of laser-clad Fe-based amorphous coatings

Fe-based amorphous coatings were synthesized with Fe44Cr30Mo20B3C3 powders at different laser powers on Q235 substrate at different laser powers. The microstructure and mechanical property of the coatings were investigated. X-ray diffraction and the thermodynamic analysis results indicate the presence of both amorphous and crystalline phases in the coating. The highest hardness up to 917 HV0.5 is obtained at 1300 W, which is about 5 times that of the substrate. From the abrasive test, the coating obtained at lower laser power exhibits shallower grooves and lower weight loss, indicating better wear resistance. The synergism of the amorphous phase and Cr23C6 contributes to the improvement of the mechanical properties. The existence of Cr and the amorphous phase also promotes the passivation phenomenon and improves the corrosion resistance of the coating.

Prediction of 18Ni300 laser cladding topography based on back-propagation neural network and particle swarm optimization

Laser cladding is an advanced new surface manufacturing technology, which has a wide range of applications in production, repair and surface strengthening of parts in many industries. Aiming at the problem that the forming quality cannot be guaranteed after the Q235 substrate, a full factorial design method was used to conduct the experiments. Then a multiple linear regression model was established to obtain the functional expression between the cladding layer morphology parameters (cladding layer height, cladding layer width and dilution ratio) and laser power, scanning speed and powder feeding rate. And then back-propagation neural network (BPNN) and particle swarm optimization (PSO) were used to establish prediction models between the morphology quality of the laser cladding layer and the process parameters. Finally, the prediction results of two models were compared with the measured value, respectively. The results showed that the average relative errors of the multiple linear regression model for the prediction of cladding layer width, height, and dilution ratio were 4.525%, 6.018%, and 5.659%, respectively, while the average relative errors predicted by the optimized neural network model were 3.177%, 7.242%, 4.679%, respectively. The goodness of fit(R2) in linear regression model were 0.8034, 0.8407, and 0.8297 respectively, while the R2 in PSO-BPNN model were 0.8134, 0.8336, and 0.9576 respectively. In this paper, the feasibility of the PSO-BPNN model in theory and practice was verified, and it provided theoretical guidance for the realization of the subsequent laser cladding closed-loop control system.

A novel high-entropy alloy composite coating with core-shell structures prepared by plasma cladding

A novel Ti(C,N)-reinforced body-centered cubic (BCC)-based Cr20Cu20Fe20Ni20Al20 high-entropy alloy (HEA) composite coating was prepared by a synchronized powder feeding plasma transferred arc (PTA) cladding. Microstructures and the wear properties of the HEA composite coating were investigated. Results showed that the HEA composite coating that exhibited dense microstructures and good metallurgical bonding with the substrate was mainly composed of BCC matrix grains containing intragranular ordered BCC (B2) cuboidal nanoprecipitates and face-centered cubic (FCC) micro/nano Ti(C,N) particles distributed along the grain boundaries. Both the Ti(C,N) particles and the cuboidal nanoprecipitates exhibited core-shell structures with the characteristics of high toughness in the core and high strength in the shell, which led to the combination of the high strength and toughness for the HEA composite coating favoring the improvement of wear resistance. The microhardness of the HEA composite coating was 3.33 times greater than that of the Q235 substrate and 127.4 HV0.1 higher than that of the pure Cr20Cu20Fe20Ni20Al20 HEA coating. The wear resistance of the HEA composite coating increased 3.03 times and 8.06 times compared with that of the pure HEA coating and substrate, respectively. The main wear mechanism of the HEA composite coating was mild abrasive wear.

Mechanical Properties and Growth Mechanism of TiB2-TiC/Fe Composite Coating Fabricated in Situ by Laser Cladding

A TiB2-TiC/Fe composite coating was successfully produced on a Q235 substrate by laser cladding through in-situ reactions among 60TiFe, B4C, Cr, Ni, and Si preset powder mixtures. Based on the available literature, scanning electron microscopy images of the mixed precursor powder and coating layer, and corresponding electron dispersive spectroscopy and X-ray diffraction results from the produced coating, the formation mechanism of the TiC-TiB2 composite during laser cladding was determined. The results show that the coating was mainly composed of α-Fe, TiB2, TiC and (Fe, Cr)7C3, where the TiB2 had a dark grey rectangular shape and TiC had a light grey spherical shape. Most of the TiC particles were attached to the TiB2, which means that TiB2 particles were formed before the TiC. The microhardness of the composite coating approached 1260 HV0.2, which shows that the microhardness of the composite coating was more than 7 times that of the Q235 substrate. Furthermore, the wear performance of the coating was obviously improved, to approximately 15 times that of the substrate.