Q235 Steel Substrate Research Articles

Magnetic assisted pulse electrodeposition and characterization of Ni–TiC nanocomposites

Ni–TiC nanocomposites (NCs) were produced using magnetic assisted pulse electrodeposition (MPED) technique on Q235 steel substrates in this paper. The microstructure, composition, microhardness, and corrosion and wear properties of the nanocomposites were investigated by means of scanning electron microscopy (SEM), scanning probe microscopy (SPM), X-ray diffraction (XRD), triboindenter in-situ nanomechanical testing, custom-made corrosion apparatus and wear test instrument. The results indicated that Ni grain size in the Ni–TiC NCs declined as particle size of the initial TiC powder was decreased from 200 nm to 30 nm. XRD results showed that Ni–TiC NCs consisted of Ni phase and TiC phase. When initial TiC particle size was 30 nm, XRD peaks were the lowest in intensity and the widest, confirming the smallest Ni and TiC grain sizes in Ni–TiC-1 composite. This composite also showed the highest TiC content and microhardness values, which were equal to 10.51 wt% and 895.4 Hv, respectively. Anticorrosion and wear behaviors were also affected by the initial TiC particle sizes. W values of Ni–TiC-1, Ni–TiC-2, and Ni–TiC-3 NCs were 0.91, 1.42, and 1.66 mg, respectively, after 24 h corrosion tests. Moreover, Ni–TiC-1 NC had the smallest corrosion potential and corrosion current density, demonstrating that it had the best corrosion resistance. In addition, Ni–TiC-1 composite showed the best wear resistance in wear tests.

Exploitation of natural gum exudates as green fillers in self-healing corrosion-resistant epoxy coatings

Recently, interest in developing green polymer coatings which provide self-healing and corrosion protection functions using bio-based renewable materials has significantly increased. In this study, microcapsules containing biopolymers from cashew gum and gum Arabic have been prepared by interfacial polymerization. The prepared microcapsules were individually and combinatorially embedded into epoxy coatings and the resulting composite coatings were then applied on Q235 steel substrates. The performance of the composite coatings was evaluated by immersing both scribed and unscribed coatings in simulated seawater. Surface analytical (SEM), physico-chemical (FTIR, XRD, XPS), and electrochemical impedance spectroscopy (EIS) techniques were used to investigate self-healing and corrosion resistance effectiveness of the polymer composite coatings. The obtained results revealed that cashew gum and gum Arabic could heal the scribed coating surface and subsequently suppressed corrosion reaction, without the aid of any catalyst or co-reactant. The performance was observed to be higher when the two gum exudates were combined. Thus, cashew gum and gum Arabic have demonstrated that they possess properties required for potential utilization in the formulation of marine anticorrosion and self-healing epoxy coatings.

High temperature microstructure evolution and thermal shock resistance of plasma sprayed Al2O3-ZrO2-CeO2 coatings

Al2O3-ZrO2-CeO2 composite coatings were prepared by plasma spraying Al2O3-ZrO2 composite powders with and without CeO2 addition. The microstructure and properties of the Al2O3-ZrO2-CeO2 coatings at high temperature and thermal shock resistance were investigated. The results show that an amorphous phase was formed in the plasma sprayed Al2O3-ZrO2 and Al2O3-ZrO2-CeO2 coatings. The Al2O3-ZrO2 coating consisted mainly of t-ZrO2, α-Al2O3, and γ-Al2O3. The Al2O3-ZrO2-CeO2 coating consisted mainly of t-ZrO2, α-Al2O3, γ-Al2O3, and CeO2. The Al2O3-ZrO2-CeO2 coating was more uniform and denser than the Al2O3-ZrO2 coating. The results after heat treatment showed that the two coatings were stable at 800 °C. With the increase of temperature, the coatings underwent phase transformation at high temperature (1000 and 1200 °C). At 1000 °C, the amorphous phase was obviously reduced, and the amorphous phase was crystallized to form nanocrystals. When the heat treatment temperature was raised to 1200 °C, the intensity of the diffraction peaks of t-ZrO2 and α-Al2O3 increased, the amorphous phase was completely crystallized, and γ-Al2O3 was transformed into α-Al2O3. The porosity of the two coatings decreased and the hardness increased after heat treatment. The thermal shock resistance of the coatings on the TC4 titanium alloy substrate was better than that on the Q235 steel substrate. The thermal shock resistance of the Al2O3-ZrO2-CeO2 coating was better than that of the Al2O3-ZrO2 coating.

Study of high temperature friction and wear performance of (CoCrFeMnNi)85Ti15 high-entropy alloy coating prepared by plasma cladding

(CoCrFeMnNi)85Ti15 high-entropy alloy (HEA) coating prepared on Q235 steel substrate via plasma cladding was investigated for its microstructure, hardness, and high temperature tribological performance. The microstructure of (CoCrFeMnNi)85Ti15 HEA consists of FCC and BCC solid solutions as well as an intermetallic sigma phase. The FCC solid solution is characterized by a lattice parameter of 3.669 Å and is enriched with Co-Cr, the BCC solid solution has a lattice parameter of 2.998 Å and is enriched with Fe-Mn, and the intermetallic sigma phase is enriched with Ni-Ti. The micro-hardness of the Q235 steel substrate, the CoCrFeMnNi HEA coating, and the (CoCrFeMnNi)85Ti15 HEA coating is 123.6 ± 6.2, 150.1 ± 7.4, and 910.5 ± 26.6 HV, respectively. As the hardness of the (CoCrFeMnNi)85Ti15 HEA coating is enhanced six times more than that of the CoCrFeMnNi HEA coating, it exhibits a lower wear rate and a better wear resistance at high temperatures. The best wear resistance, which corresponds to a wear rate of 4.08 × 10−6 mm3·N−1·m−1, is obtained at 400 °C. The wear mechanisms of the (CoCrFeMnNi)85Ti15 HEA coating are predominantly oxidation wear and contact fatigue, although there is evidence of oxidation wear and adhesive wear at 800 °C.

Microstructural and Corrosion Behavior of High Velocity Arc Sprayed FeCrAl/Al Composite Coating on Q235 Steel Substrate

High velocity arc spraying was used to prepare FeCrAl/Al composite coating on Q235 steel substrate by simultaneously spraying FeCrAl wire as the anode and Al wire as the cathode. The composite coating was sprayed with varying voltage and current to obtain optimum coating characteristics. FeCrAl coating was also prepared for comparison purposes. The surface microstructure of the coatings was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The average microhardness of the coatings and the substrate was analyzed and compared. Corrosion resistance was investigated by means of electrochemical tests. The image results showed that a lamellar structure consisted of interwoven layers of FeCrAl and Al. Al and FeCr constituted the main phases with traces of oxides and AlFe intermetallic compounds. The average porosity was reduced and microhardness of the coatings was improved with increasing voltage and current. The FeCrAl/Al coating formed alternating layers of hard and ductile phases; the corrosion resistance of the coatings in the sodium chloride (NaCl) solution depended on the increase in Al content and spray parameters. The corrosion resistance tests indicated that FeCrAl/Al coating had a better corrosion resistance than the FeCrAl coating. FeCrAl/Al can be used to coat steel substrates and increase their corrosion resistance.

Combined effect of heat treatment and sealing on the corrosion resistance of reactive plasma sprayed TiNx/TiOy coatings

A titanium nitride/titanium oxide composite coating was deposited on a Q235 steel substrate by reactive plasma spraying (RPS). The microstructure and phases of the coatings were analysed by optical microscopy, scanning electron microscopy, and X-ray diffraction. The corrosion performance of the coatings was evaluated through electrochemical measurements. The as-sprayed coating is composed of TiN, TiN0.3, and Ti3O phases. Ti2O and TiO2 were generated after heat treatment at 300 and 400 °C, respectively. Heat treatment reduced the porosity of the coating. Sealing the coating before and after the heat treatment led to improved corrosion resistance. The coating heat-treated at 300 °C and then sealed had the lowest porosity (0.8%), with a reduction in porosity of 55.6% compared to that of a sealed as-sprayed coating (1.8%). The corrosion current density and corrosion potential of the sealed as-sprayed coating were found to be 6.03 × 10−7 A/cm2 and −0.47 V, respectively, whereas the coating heat-treated at 300 °C and then sealed had the lowest corrosion current density (1.8 × 10−8 A/cm2) and the highest corrosion potential (−0.19 V). Thus, the results indicate that sealed heat-treated coatings have much better corrosion resistance than the sealed as-sprayed coating.

Effect of SiC particle size on structures and properties of Ni–SiC nanocomposites deposited by magnetic pulse electrodeposition technology

Abstract In this paper, Ni–SiC nanocomposites were deposited on Q235 steel substrates by magnetic pulse electrodeposition (MPED) technique. Microstructures, compositions and microhardness values of obtained composites were determined by scanning electron microscopy (SEM), scanning probe microscopy (SPM), X-ray diffraction (XRD), and triboindenter in-situ nanomechanical testing. Results showed S-30 nanocomposites with fine, compact and uniform structures consisting of fine nickel grains (average size: 381.7 nm) and SiC nanoparticles (average size: 34.2 nm). For SiC particle size of 30 nm, diffraction peaks of Ni and SiC appeared wide with low intensity, indicating S-30 nanocomposites with small sized Ni grains and SiC nanoparticles. Largest TiN content reaching 10.59 wt% was embedded in S-30 nanocomposites prepared at SiC particle size of 30 nm. Final depths of S-30 and S-200 composites were estimated to 15.1 μm and 24.8 μm, respectively. Wear and corrosion properties of Ni–SiC nanocomposites were then investigated. After corrosion testing for 24 h, the weight losses of S-200, S-80 and S-30 composites were recorded as 1.67, 1.44 and 0.95 mg, respectively. Under the same wear experimental conditions, S-200 composite presented the highest mass loss while S-80 composites displayed the lowest mass loss. By comparison, wear mass loss of S-30 nanocomposites was only 37.1 mg.

Enhanced Mechanical and Electrochemical Performances of Silica-Based Coatings Obtained by Electrophoretic Deposition.

To solve the existing problems of silicon dioxide (SiO2) coating fabricated by the sol-gel method, such as complicated process, long production cycle, uncontrollable quality, etc., an improved electrophoretic deposition (EPD) combined with the sintering process was proposed to prepare SiO2 coating on a dark nickel (Ni)-coated Q235 steel substrate. Silica sol was prepared by basic catalysis, containing silica of ∼130 g L-1 with viscosities below 4 mPa s. Silica sol powder was characterized by the differential thermal analysis, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. EPD was applied to prepare SiO2 coating on the Ni adhesive layer, followed by the sintering process to improve the compactness. In addition, the effects of EPD and sintering parameters were also evaluated. Potentiodynamic polarization and electrochemical impedance spectra were utilized to assess the corrosion behavior of the coating. The results showed that the EPD coating demonstrated excellent wear resistance when deposited at 15 V for 40 s and sintered at 400 °C for 45 min, exhibiting ∼6 μm thickness and a compact morphology. It also showed superior corrosion resistance with icorr of 1.02 × 10-7 A cm-2, which was 2 orders of magnitude lower than that of dip-coating. Combining the EPD and sintering processes could shorten the fabrication period of SiO2 inorganic coating and also improve the mechanical and corrosion properties, providing guidance for inorganic ceramic fabrication and showing potential for practical applications.

Physical and Electrochemical Performances of Cold Sprayed Pb Electrodes

Titanium-based PbO2 electrodes are widely used for chemical industries, such as electrodialysis, electrolysis, and electrodepositing, to improve the mechanical and life cycle properties of Pb metal electrodes. However, PbO2 electrodes are usually electrodeposited onto rigid metals due to its soft characteristic, which results in severe passivation problems requiring thin thickness and high porosity. It is of great importance to develop a rigid Pb metal electrode system since thermal spraying and welding methods fail to manufacture such a promising electrode. In the present work, the cold spraying method was used to deposit a pure Pb metal coating with thickness of above 500 μm on Q235 steel substrate. The coating has good physical performances, the porosity is less than 1%, and the bonding strength ranges from 6.25 to 7.75 MPa. The cross-sectional morphology suggests that no through-thickness pores exist in the coating. The oxygen evolution potential is larger than 1.5 V vs. SCE, which is similar to the potential of the titanium-based PbO2 electrode. Dynamic polarization curves and cyclic voltammetry curves of coated sample in sodium sulfate solution indicate that cold sprayed Pb coating is a good electrode for electrochemical reduction reactions. All our results mean that cold spraying is capable of manufacturing electrode materials for electrochemical industries.

Effect of coating process on the properties of multi-walled carbon nanotubes/waterborne polyurethane anticorrosive and conductive coating

A thicker layer of multi-walled carbon nanotubes (MWCNTs)/waterborne polyurethane (WPU) anticorrosive and conductive coating was respectively prepared on the Q235 steel substrate by brushing (Br) and electrostatic spraying (ES) in this work. The effect of coating process on the dispersion of the MWCNTs and the electrical conductivity, corrosion resistance, and bond strength of the coating was investigated. It was shown that the coating prepared by ES (ES coating) had a smooth surface, few defects and evenly dispersed MWCNTs. The coating prepared by Br (Br coating) had a rough surface, some defects and obviously agglomerated MWCNTs. The electrical conductivity, corrosion resistance, and bond strength of the ES coating were higher than those of the Br coating with the same MWCNT content. As the MWCNT content increased, the electrical conductivity of the ES coating increased, however, its corrosion resistance and bond strength first increased and then decreased. The resistivity of ES 0.3 wt% MWCNTs/WPU coating (12808.4 Ω·m) met the standard requirement of the conductive coating. Its corrosion rate was 3.50×10-5 mm/a immersed in 3.5 wt% NaCl solution. Its bond strength to the Q235 steel substrate was higher than that of ES pure WPU coating. As the MWCNT content increased, the electrical conductivity of the Br coating increased, however, its corrosion resistance and bond strength decreased. When the MWCNT content was 0.6 wt%, the Br coating would conduct electricity. Its corrosion rate was 5.24×10-2 mm/a.

Microstructure and Corrosion Behavior of (CoCrFeNi)95Nb₅ High-Entropy Alloy Coating Fabricated by Plasma Spraying.

In this paper, the (CoCrFeNi)95Nb5 high-entropy alloy (HEA) coating with a thickness of 500 μm on Q235 steel substrate was fabricated by plasma spraying. The microscopic results showed that a new Laves phase is formed in the (CoCrFeNi)95Nb5 HEA coating compared to the HEA powder, and elemental segregation occurs between the dendrites and the interdendrites of the coating, while the interdendritic phase enriches with the Cr and Nb. The phase composition change and elemental segregation behavior were mainly due to the faster cooling rate of the plasma spraying technique. At the junction of the coating and the substrate, the HEA coating bonded well to the substrate; in addition, the width of transition zone was merely 2 μm. The microhardness of the (CoCrFeNi)95Nb5 HEA coating was 321 HV0.5, which is significantly higher than that of the substrate. In terms of corrosion resistance, the (CoCrFeNi)95Nb5 HEA coating has good corrosion resistance in NaCl solution. Although the corrosion form was pitting corrosion, the pitting potential of the (CoCrFeNi)95Nb5 HEA coating was significantly higher than that of other coatings, which was mainly because of the dense passivation film formed by Cr and Nb on the surface of the coating. Once the passivation film was destroyed by Cl−, the selective corrosion occurred on the surface of the (CoCrFeNi)95Nb5 HEA coating. In summary, the (CoCrFeNi)95Nb5 HEA coating prepared by plasma spraying technology can significantly improve the corrosion resistance and mechanical properties of the Q235 steel substrate.

Microstructure and corrosion property of CrMnFeCoNi high entropy alloy coating on Q235 substrate via mechanical alloying method

The CrMnFeCoNi high entropy alloys with equal atomic ratio is one of the most notable and promising alloys that has been studied by researchers so far. However, there are only a few papers that has been published on CrMnFeCoNi high entropy alloy coating. In this paper, the equal atomic ratio CrMnFeCoNi alloy coating was synthesized on the Q235 steel substrate by mechanical alloying method. The experiment for preparing CrMnFeCoNi HEA coating involved two steps: First, high-entropy alloy powder was prepared. Then the Q235 substrate was put into the prepared powder and followed by a milling process for 10 h, after that the high entropy alloy coating was successfully prepared. The microstructures of the coating were characterized by scanning electron microscope (SEM), the phase structure and chemical composition of which were analyzed by X-ray diffraction (XRD) and energy dispersive spectrometer (EDS) respectively. The as prepared CrMnFeCoNi powder and the final coating are both single face-centered cubic (FCC) solid solutions. The thickness of the coating is 180 μm and showed a good bonding performance with the substrate. The elements in the coating were evenly distributed without component segregation. The corrosion behaviour was tested by the dynamic potential polarization method. The results showed that the CrMnFeCoNi coating has better corrosion resistance than the substrate in 3.5 wt % NaCl solution.

Microstructure and Properties of CoCrFeNi(WC) High-Entropy Alloy Coatings Prepared Using Mechanical Alloying and Hot Pressing Sintering

The CoCrFeNi high-entropy alloy coatings (HEACs) with different weight ratios (10 and 30 wt.%) of WC additions have been prepared using mechanical alloying and a vacuum hot pressing sintering technique on a Q235 steel substrate. The microstructures, microhardness, wear resistance, and corrosion resistance of HEACs were studied. The CoCrFeNi(WC) powders were obtained by mixing the CoCrFeNi HEA powders and WC particles. The sintered products of both HEACs with high relative density contained one solid solution phase with face-centered cubic structure, WC, and unknown precipitate phases. The transition boundary had a good metallurgical bonding with the coating and substrate. The average microhardness values of CoCrFeNi HEACs with 10 and 30 wt.% WC additions reached 475 and 531 HV respectively, which were far higher than that of the substrate (160 HV). Moreover, both coatings exhibited better wear resistance than the substrate under the same wear conditions. The 30 wt.% WC HEAC displayed the lower friction coefficient, and the shallower wear groove depth. The grain refinement strengthening and second-phase particle strengthening could be beneficial to the enhanced hardness and wear resistance of coatings with WC additions. The corrosion behavior of the tested samples in the 3.5 wt.% NaCl solution were investigated using electrochemical polarization measurements. The CoCrFeNi(WC) coatings all revealed the improved corrosion resistance. Especially, a 10 wt.% WC addition remarkably enhanced the comprehensive corrosion resistance and easy passivation of CoCrFeNi HEAC.

Properties of Waterborne Polyurethane Conductive Coating with Low MWCNTs Content by Electrostatic Spraying.

Because flammable organic solvents are emitted during the construction process, oil-based conductive coatings generally result in potential safety problems. A high content of conductive mediums can also weaken the adhesive and protective abilities of existing conductive coatings. Therefore, an anticorrosive and conductive coating was prepared on Q235 steel substrate by spraying the multi-walled carbon nanotubes (MWCNTs)/waterborne polyurethane (WPU) dispersion with a low MWCNT content in this work. The effect of the MWCNT content on the electrical conductivity, corrosion resistance, and adhesive strength of the WPU conductive coating was investigated. It was concluded that a spatial network structure of MWCNTs-WPU was formed to make the coating structure more compact. The electrical conductivity, corrosion resistance, and adhesive strength of the WPU conductive coating first increased and then decreased as the MWCNT content increased. When the MWCNT content was only 0.2 wt % (which was far lower than that of the existing conductive coatings at 1 wt %), the coating began to conduct electricity; its resistivity was 12,675.0 Ω·m. The best combination property was the 0.3 wt % MWCNTs/WPU conductive coating. Its adhesive strength was 19.99% higher than that of pure WPU coating. Its corrosion rate was about one order of magnitude lower than that of pure WPU coating after being immersed in 3.5 wt % NaCl solution for 17 days.

The microstructures and anti-corrosion behavior of the thermal sprayed Hastelloy C276 coating on substrate of Q235 steel

Hastelloy C276 coating was prepared on the substrate of Q235 steel by arc thermal spraying process. The microstructure, microhardness, thermal shock resistance and anti-corrosion of the coating were investigated. The coating exhibits a layered buildup structure with some pores and unmelted particles appearing. There is a distinct and rough interface between the coating and the substrate which increases the contact area between the coating and the substrate. The coating and the substrate were meshed to each other in the boundary, showing a strong bonding. The coating exhibited a strong thermal shock resistance with the substrate of Q235 steel at 600 °C. The microhardness of the surface of the coating is much higher than the microhardness of the surface of the substrate. Uniform corrosion method of laboratory semi-immersion test was used to test the corrosion resistance of C276 coating. The coating exhibited good corrosion resistance in concentrated HCl with a concentration of 36.5%.

Anti-corrosion performance of aniline trimer-containing sol–gel hybrid coatings for mild steel substrate

Novel electroactive sol–gel hybrid coatings were synthesized by hydrolysis and condensation reaction of tetraethoxysilane (TEOS) and different mass ratios of silane-capped aniline trimer (TSUPQD) on the surface of Q235 steel. Microstructure, thermal stability, and corrosion resistance of as-prepared hybrid coatings were characterized by FTIR, UV–Vis, SEM, TGA, CA measurement, polarization curve, and electrochemical impedance spectroscopy. It could be seen that the icorr value of as-prepared novel coating was markedly lower than those of pure TEOS-based coating and bare substrate. EIS results indicated that the impedance of hybrid coating was higher than that of Q235 steel substrate, indicating the effective protective property for substrate. Meanwhile, the aniline trimer-based hybrid coatings presented much higher impedance after immersion in 3.5 wt% NaCl for 200 h, and the best corrosion performance was acquired when the mass ratio of TEOS/TSUPQD is 100:4. The XRD and SEM analysis of the corrosion product beneath the hybrid coatings showed that the redox catalytic capability of aniline trimer could induce the Q235 substrate to form the passive films which mainly consisted of Fe2O3 and Fe3O4.

Effect of sintering temperature on the microstructure and performance of a ceramic coating obtained by the slurry method

In this paper, SiO2, Cr2O3, Al2O3, and MgO were used as ceramic aggregates, and a small amount of Al powder was added. A ceramic coating was prepared on a Q235 steel substrate. The effect of the sintering temperature on the coating microstructure, phase structure and wear resistance was studied by Scanning Electron Microscope (SEM), X-ray Diffraction (XRD) and friction and wear testing. The results show that the tensile strength of the ceramic coating is increased after sintering, the structure becomes dense, and the size of coated micropores is increased to release the internal tensile stress. With the increase of the sintering temperature and tensile stress, the micropores begin to release the excess tensile stress in the form of crack initiation and expansion. The mineralization of MgO, Cr2O3, nMgO and mSiO2 phases can be achieved by sintering the coating at 200 °C; the oxygen in the atmosphere migrates along the micropores in the coating to react with Fe in the steel substrate, forming FeO, and the resulting FeO reacts with the SiO2 in the coating to form the Fe2SiO4 phase. The coating has the best wear resistance after being sintered at 400 °C, and the abrasion resistance of the sample is 6.7 times higher than that of the sample dried at room temperature.

Effect of Nano-Y2O3 on Microstructure and Crack Formation in Laser Direct-Deposited In Situ Particle-Reinforced Fe-Based Coatings

In situ hard-particle-reinforced Fe-based composite coatings were prepared on Q235 steel substrates by direct laser deposition using Fe-based alloy powders containing 2 wt.% B, 3 wt.% Si and 1-3 wt.% nano-Y2O3. The microstructures, phase compositions, hardnesses and wear resistances of the deposited coatings with different nano-Y2O3 contents were studied using metallographic microscopy, scanning electron microscopy, x-ray diffraction, transmission electron microscopy, microhardness tests and pin-on-disk abrasion tests (MMW-1A), respectively. The results showed that the appropriate addition of Y2O3 played a role in grain refinement and in decreasing the number of brittle phases and impurity elements in the grain boundaries. Consequently, the number of cracks in the laser-deposited coating also decreased. The Fe-based composite coatings were mainly composed of α-Fe, γ-Fe and in situ-produced reinforced particle phases, such as Cr23C6, Cr7C3, (Cr, Fe)7C3, Fe2B, and CrFeB. When the content of nano-Y2O3 was 2 wt.%, a Fe-based composite coating with a thickness of 4 mm that was free of cracks was obtained, and its surface hardness reached 650HV. Moreover, the wear resistance of the coating with 2 wt.% nano-Y2O3 was the best among the samples studied. The presence of nano-Y2O3 increased the solubility of Cr and Si in the solid solution, which eliminated the residual austenite region, and as a result, the phase transformation from γ-Fe to α-Fe was restrained and the transformation stress was also limited, thereby decreasing the probability of cracks in the coatings.

Effect of Y2O3 on Microstructure and Properties of Fe-Al-Si-B Cladding by Plasma Transferred Arc

Fe-Al-Si-B in situ composite coating was prepared with plasma arc cladding on Q235 steel substrate. Moreover, rare earth oxide Y 2 O 3 powder was added to the cladding powder in order to improve the microstructure and properties of the coating. The effect of Y 2 O 3 on the microstructure and properties of the Fe-Al-Si-B cladding by plasma transferred arc was investigated. The microstructure, phase constituent, microhardness and wear property of the coating were examined by optical microscope (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), micro hardness tester, friction and wear tester, respectively. The result indicates that the addition of Y 2 O 3 can purify the grain boundaries and homogenize the inclusions, and thus the shape and distribution of the inclusions are improved significantly. Furthermore, a dense, uniform, defect-free and significantly refined coating is then formed. When the content of Y 2 O 3 reaches 0.9wt%, the hardness of the coating reaches 5.10 GPa, and the optimum wear resistance is obtained.

The anti-corrosion behavior under multi-factor impingement of Hastelloy C22 coating prepared by multilayer laser cladding

Hastelloy C22 coating was prepared on substrate of Q235 steel by high power multilayer laser cladding. The microstructure, hardness and anti-corrosion properties of coating were investigated. The corrosion tests in 3.5% NaCl solution were carried out with variation of impingement angle and velocity, and vibration frequency of sample. The microstructure of coating changes from equiaxed grain at the top surface to dendrites oriented at an angle of 60° to the substrate inside the coating. The corrosion rate of coating increases with the increase of impingement angle and velocity, and vibrant frequency of sample. Corrosion mechanisms relate to repassivation and depassivation of coating according to electrochemical measurements. Above results show that multilayer laser cladding can endow Hastelloy C22 coating with fine microstructures, high hardness and good anti-corrosion performances.