Surface Of Q235 Steel Research Articles

Effect of Preheating Temperature on Microstructure of Fe Based Alloy Coating by Laser Direct Metal Deposition

A Fe60 alloy coating was deposited on the surface of Q235 steel by semiconductor laser under the different preheating temperature at 25°C, 100°C, 150°C, 200°C, 250°C, 300°C respectively. The structure and hardness of the samples were analyzed by the means of OM、SEM、XRD、micro-hardness tester. The results show that: A Fe60 alloy coating with high Cr and C content was prepared on the steel substrate by using optimized process parameters, the interface bonding was formed between the coating and the substrate, the thickness of the coating without cracks and porosities is about 6-10mm. There are equiaxed and dendrite crystals in the coating and the phase of coating is composed of α-Fe, γ-Fe,{Fe,Ni} solid solution, Fe3C, Cr2B, Cr7C3. Preheating treatment has good eliminating coating cracks role in the laser deposited Fe-based coating with high Cr and C content, the sample preheated at 200°C has the finest crystalline structure, and the thickness is 8mm and the hardness is up to 806HV. Preheating treatment is an effective method to eliminate the cracks in the high thickness Fe60 alloy coating by laser direct deposition.

FABRICATION AND WEAR BEHAVIOR ANALYSIS ON AlCrFeNi HIGH ENTROPY ALLOY COATING UNDER DRY SLIDING AND OIL LUBRICATION TEST CONDITIONS

In this paper, AlCrFeNi high entropy alloy coating was fabricated on the surface of Q235 steel using hot pressing sintering process. The coating has the controlled thickness size and excellent mechanical properties. Scanning electron microscopy (SEM), XRD and hardness testing method were used to study the morphology, phase structure and hardness of high entropy alloys coating. The lattice distortion plays a significant role in increasing the hardness. Coating formation mechanism caused by the element diffusion under the hot pressing effect is also discussed in the paper. Simultaneously, the dry sliding and oil lubrication wear tests, wear morphology observation and wear mechanism discussion were completed. As the result shows, AlCrFeNi high entropy alloys coating exhibits superior wear resistance either at dry sliding or oil lubrication tests owing to its hard high entropy solid solution structure.

Microstructure and property of Ni60A/WC composite coating fabricated by fiber laser cladding

Laser clad Ni60A/WC composite coating was fabricated on the surface of Q235 steel by using 6 kW fiber laser. The morphology, composition, and microhardness of composite coating were studied by using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X‐ray diffraction (XRD), and micro‐hardness tester. The results show that in the process of fiber laser cladding Ni60A/WC composite coating, residual WC particles partially dissolve and react with other elements to form eutectics, which exists in the shape of lumpy, strip and spherical. The main structures of laser cladding are γ‐Ni, WC, W2C, M7C3, M23C6 etc. From the hardness analysis, the average hardness of the composite coating is four times of the substrate.

In situ synthesis of WC ceramic particle reinforced composite coating by GTAW

WC ceramic particles reinforced composite coatings were in situ synthesised on the surface of Q235 steel by GTAW processing using mixtures of W, C, Ni, B–Fe and a small amount of Si iron. Microstructures and phase of the coating were analysed by scanning electron microscope, energy dispersive spectrometer and X-ray diffractometer. Furthermore, microhardness and abrasion resistance also were studied using microhardness tester and abrasive tester, respectively. The results showed that the coating was no pore and crack free. The coating consisted of FeNi matrix, M7C3, Ni2Si, Ni3B, Fe2B and WC blocky particles. Owing to the uniform distribution of in situ synthesised carbide particles, high hardness and excellent wear resistance were achieved. The maximum hardness of the coating was 1578.8 HV0.2. The relative wearability of the composite was 23.5 times higher than Q235 steel substrate which showed good wear resistance.

Controlled release and synergistic effects of polyvinyl alcohol (PVA) on phosphate corrosion inhibitor at the interface of thermal insulation and carbon steel

Purpose – This paper aims to study the controlled release and synergistic effect of water-soluble polyvinyl alcohol (PVA) on phosphate corrosion inhibitor at the interface of thermal insulation cotton/carbon steel. Design/methodology/approach – This study was carried out using a coating method, scanning electron microscopy, energy dispersive spectroscopy and AC impedance. Findings – The single-phase phosphate particles were coated/adsorbed on the PVA film, which was formed on the fiber surface of corrosion inhibitor/PVA-impregnated rock wool sample. On the surface of Q235 steel, an effective protective film was formed by the corrosion inhibitor with partially dissolved PVA that can significantly increase the polarization resistance of corrosion reaction, and reduce the capacitive reactance of electric double layer. The rock wool impregnated with the phosphate corrosion inhibitor and 1.5 per cent PVA showed obvious controlled release and inhibition synergism. Originality/value – The rock wool impregnated with the phosphate corrosion inhibitor and 1.5 per cent PVA showed the following advantages: the adsorption and release quantities of the corrosion inhibitor increased by 3.3 and 2.9 times, respectively; the release-adsorption equilibrium time increased from 2 to 6 h; and the corrosion inhibition efficiency increased from 61.55 per cent to 94.6 per cent.

Microstructure and Wear Resistance of Nanostructure WC Composite Coatings Prepared by Argon Arc Cladding Injection

Nanostructure WC composite coatings were prepared on surface of Q235 steel by argon arc cladding injection using microstructure WC feeding which were prepared by nanostructure WC powder. The microstructure of the coating were analyzed by scanning electron microscopy (SEM). Phase of the coating were analyzed by energy dispersive spectrometer and X-Ray diffract meter, moreover, microhardness and wear resistance were texted by Microhardness tester (HVST-1000) and friction wear testing machine (MMS-2A). The results show that the combination of coating and substrate is metallurgical bonding. and no Pores and cracks were founded in bonding area. aggregated nanostructure WC particles and nanostructure WC particles uniformly distributed in the coating. The maximum hardness of the coating is 1461 HV. Compared with the Q235 steel, the wear resistance of the coating increased about 15 times.

The Preparation of Phosphate Bonding Agent and its Application in Ceramic Coating

A kind of phosphate bonding agent was prepared with H3PO4 and Al(OH)3 as the main raw materials in this paper. Phosphate-metal matrix ceramic coating was prepared on the surface of Q235 steel by using the technology of ambient cure with phosphate bonding agent as main body and CuO and SiC as fillers. The influence of the addition of CuO on curing temperature was studied. Meanwhile, the influence of SiC particle size and content on the abrasion resistance of the coating was studied. The result showed that the amount of friction and wear of phosphate-metal matrix ceramic coating was 5.5mg, when the the molar ratio of P and Al was 3:1.3, SiC particle size was D50=18μm, and its particle content was 40%, 20%wt CuO was added.

The Investigation on Wear Resistance of Fe-Based Alloy Coating by Argon Arc Cladding

By argon arc cladding technology, a Fe-based alloy coating was prepared on the surface of Q235 steel. The microstructure of the cladding coating was investigated by optical microscope (OM) and scanning electron microscope(SEM). The microhardness and wear resistance performance of the coating were tested by microhardness tester and friction-wear tester. The results show that the alloy coating with martensite, alloy solid solution and (Cr, Fe) 7C3/Fe3C/ Fe2B compounds is prepared on the surface of Q235 steel, the microhardness of the coating reaches as high as 600 HV and the wear resistance of the coating is about 8 times higher than that of Q235 steel substrate. When deposited a wear-resistant layer on the surface of mild steel , the high plasticity and ductility are preserved as well as the hardness and wear resistance of the cladding layer are improved greatly.

Microstructure Analysis of TiC Reinforced Ni-Based Composite Coating by Plasma Cladding

TiC reinforced Ni-based composite coating added with 10% TiC and 20% TiC particles were prepared on the surface of Q235 steel by plasma cladding, respectively. SEM as well as EDS and XRD were used to investigate the microstructure and formation mechanism of composite coating. The results show that between composite coating and substrate is metallurgical combination, and the microstructure of composite coating is composed of basic microstructure dendrite γ-Ni, interdendritic eutectic structure (α-Fe+Cr23C6+CrB) and dispersed TiC particle. Part of TiC particles melt when the composite coating added with 10% TiC particles, in the composite coating added with 20% TiC particles, part of TiC particles precipitate after dissolution. TiC particles have a uniform distribution with the size 3~5µm. The maximum value of micro-hardness of composite coating added with 10% TiC and 20% TiC particle is 460 HV0.2 and 620 HV0.2, respectively.

Microstructure and Hardness of TiC/Ni-Based Coating by Plasma Cladding

TiC reinforced Ni-based composite coating added with 10% TiC particles was prepared on the surface of Q235 steel by plasma cladding. SEM as well as EDS and XRD were used to investigate the microstructure and formation mechanism of composite coating. The results show that between composite coating and substrate is metallurgical combination, and the microstructure of composite coating is composed of basic microstructure dendrite γ-Ni, interdendritic eutectic structure (α-Fe+Cr7C3+Fe3C) and dispersed TiC particle. The maximum value of micro-hardness of composite coating added with 10% TiC particle is 440 HV0.2.

Researches on Aluminum Coating by Flame Spraying on Q235 Steel Surface

The flame spraying aluminum coating on surface of Q235 steel was investigated by morphology analysis, saline soak test and salt-fog corrosion test. The results shown that comparing to Q235 steel, corrosion resistance of the aluminum flame spraying coating formed was raised.

Improving corrosion resistance of Q235 steel by Ni-Cr alloyed layer

Ni-Cr alloyed layer was formed on surface of Q235 steel by double glow plasma surface metallurgy to improve the corrosion resistance of substrate. The composition and microstructure of alloyed layer was analyzed by SEM and XRD. Potentiodynamic polarization and electrochemical impedance spectroscopy was applied to evaluate the corrosion resistance of the alloyed layer. The results showed working pressure had a great effect on structure of Ni-Cr alloyed layer, and the dense and smooth alloyed layer was prepared at 50 Pa working pressure. Compared with substrate, Ni-Cr alloyed layer exhibited higher corrosion potential, lower corrosion current density and larger charge transfer resistance, which indicated that Ni-Cr alloyed layer significantly modified the corrosion resistance of Q235 steel.

Microstructure Analysis of TiC Reinforced Fe-Based Composite Coating by Plasma Cladding

TiC reinforced Fe-based composite coating with 10% and 20% TiC particle were prepared on the surface of substrate Q235 steel by plasma cladding, respectively. The microstructure and formation mechanism of cladding layer were carefully investigated by SEM, EDS and XRD. The results show that metallurgical combination is achieved between coating and substrate, the microstructure of composite coating is composed of dendrite α-Fe, interdendritic eutectic structure (α-Fe, Cr23C6 and CrB) and added TiC particles, and microstructure refinement with the increase of TiC particles content. TiC particles react with Fe-based alloy and part of TiC particles dissolve into coating. The hardness of composite coating has a relationship with TiC particles content and TiC particles distribution, and hardness increase with the increase of TiC particles content. The maximum value of composite coating hardness is 545 HV0.2 and 719 HV0.2, respectively. The major strengthening mechanism is fine-grain strengthening, solid solution strengthening and dispersion strengthening.

TEM Analysis and Corrosion Resistance of the Ceramic Coatings on Q235 Steel Prepared by Hybrid Method of Hot-Dipping Aluminum and Plasma Electrolytic Oxidation

The hybrid method of plasma electrolytic oxidation (PEO) and hot-dipping aluminum (HDA) was employed to deposit composite ceramic coatings on the surface of Q235 steel. The cross-section microstructure and surface morphology of the treated specimens were investigated with scanning electron microscopy (SEM). Especially, the composition of the composite coatings was investigated with transmission electron microscopy (TEM). The corrosion resistance was analyzed by immersing and corrosion polarizing experiments. The results indicate that metallurgical bonding can be observed between the ceramic coatings and the steel substrate. There are many micro-pores which act as discharge channels in the PEO coatings. The phase composition of the ceramic coatings is mainly composed of amorphous phase and crystal Al2O3 oxides. The crystal Al2O3 phase includes κ- Al2O3, θ- Al2O3 and β- Al2O3.The corrosion resistance of the PEO samples is much better than that of the HDA samples whether immersed in the NaCl solution or in the sea water.

Microstructure and Performance of Fe-Based Composite Clad Layer Fabricateded by Submerged-Arc Welding Added Alloy Powder

TiC particle reinforced Fe-based composite clad layer were in situ synthesized on surface of Q235 steel by Submerged arc Welding of the mixed powder of ferrotitanium, iron, chromium, nickel and colloidal graphite, etc. Microstructure of the clad layer were observed by scanning electron microscope （SEM） and Energy Disperse Spectroscopy (EDS). Wear resistance of the clad layer was tested on wear tester at room temperature compared with the base material Q235 steel. Microhardness of the clad layer was measured by microhardness tester. Results indicated that the fine TiC particles were formed by Submerged-arc Welding process, and the the TiC particles were dispersed in the matrix. The size of TiC particles was less than 2 μm. The microstructure of cladding layer consisted of TiC particles, martensite and austenite. The average microhardness of clad layer was HV0.2601, which was about 3 times as high as the based metal Q235. On the conditions of same wear and room temperature, the weight loss of the base material Q235 is 10-15 times as much as the composite clad layer. The weight loss increase of the clad layer has a little change with the increase of load and the change of load is not sensitive to the weight loss of the clad layer. The clad layer has good load characteristics.

The Effects of Sulfate Reducing Bacteria on Crevice Corrosion Behavior of Q235 Steel

The crevice corrosion behavior of Q235 carbon steel has been studied under the simulated disbonded coating with an aperture of 1.0mm in the soil-extract solution (SES) with and without sulfate-reducing bacteria (SRB) by using the electrochemical impedance spectroscopy (EIS). The surface morphologies of the steel after experiment were observed by scanning electron microscopy (SEM).The results showed that the capacitive arc of the Q235 steel electrode in SRB containing solution is smaller than that in the aseptic solution at the initial stage of test. However, after 19 days, the capacitive arc of the steel in bacteria containing solution becomes bigger than that in the aseptic solution, and corrosion rate of the steel was smaller in the SES with SRB than that without SRB. The degree of the corrosion on the surface of steel Q235 was more severe after 44 days in the SES without SRB than that with SRB. However, corrosion pits were found on the surface of Q235 steel in the SES with SRB.

TEM analysis and wear resistance of the ceramic coatings on Q235 steel prepared by hybrid method of hot-dipping aluminum and plasma electrolytic oxidation

The hybrid method of PEO and hot-dipping aluminum (HDA) was employed to deposit composite ceramic coatings on the surface of Q235 steel. The composition of the composite coatings was investigated with X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The cross-section microstructure and micro-hardness of the treated specimens were investigated and analyzed with scanning electron microscopy (SEM) and microscopic hardness meter (MHM), respectively. The wear resistance of the ceramic coatings was investigated by a self-made rubbing wear testing machine. The results indicate that metallurgical bonding can be observed between the ceramic coatings and the steel substrate. There are many micro-pores and micro-cracks, which act as the discharge channels and result of quick and non-uniform cooling of melted sections in the plasma electrolytic oxidation ceramic coatings. The phase composition of the ceramic coatings is mainly composed of amorphous phase and crystal Al2O3 oxides. The crystal Al2O3 phase includes κ-Al2O3, θ-Al2O3 and β-Al2O3. The grain size of the κ-Al2O3 crystal is quite non-uniform. The hardness of the ceramic coatings is about HV1300 and 10 times higher than that of the Q235 substrate, which was favorable to the better wear resistance of the ceramic coatings.

The Research on Coating of Electroless Ni-W-P Ternary Alloys

The ternary Ni-W-P alloy coatings were deposited on the surface of Q235 steel using Chemical deposition. The microstructure, phase analysis, plating velocity and hardness were investigated with scanning electron microscope, X-ray diffraction technique and Vickers hardness tester. The results showed that the plating rate had been increased firstly, and then decreased with the increment of sodium citrate concentration in the range of 20-80g/L, the maximum plating velocity was 9.14μm/h. The hardness of Ni-W-P plating increased first and then decreased with the increment of sodium citrate concentration, the maximum hardness was 643HV when the concentration of sodium citrate was 40g/L. When the concentration of sodium citrate was 40g/L, the substrate was completely covered by Ni-W-P plating, the surface was composed of uniform crystalline grains, and had no obvious defects and presented amorphous. The coating and substrate were relatively strong, the coating had no the phenomena of fall off and crackle in the bending and files tests when the concentration of sodium citrate was 40g/L and 50g/L respectively.

Evolution of micro-arc oxidation behaviors of the hot-dipping aluminum coatings on Q235 steel substrate

Micro-arc oxidation (MAO) is not applicable to prepare ceramic coatings on the surface of steel directly. In this work, hybrid method of MAO and hot-dipping aluminum (HDA) were employed to fabricate composite ceramic coatings on the surface of Q235 steel. The evolution of MAO coatings, such as growth rate, thickness of the total coatings, ingrown and outgrown coatings, cross section and surface morphologies and phase composition of the ceramic coatings were studied. The results indicate that both the current density and the processing time can affect the total thickness, the growth rate and the ratio of ingrown and outgrown thickness of the ceramic coatings. The total thickness, outgrown thickness and growth rate have maximum values with the processing time prolonged. The time when the maximum value appears decreases and the ingrown dominant turns to outgrown dominant little by little with the current density increasing. The composite coatings obtained by this hybrid method consists of three layers from inside to outside, i.e. Fe–Al alloy layer next to the substrate, aluminum layer between the Fe–Al layer and the ceramic coatings which is as the top exterior layer. Metallurgical bonding was observed between every of the two layers. There are many micro-pores and micro-cracks, which act as discharge channels and result of quick and non-uniform cooling of melted sections in the MAO coatings. The phase composition of the ceramic coatings is mainly composed of amorphous phase and crystal Al2O3 oxides. The crystal Al2O3 phase includes κ-Al2O3, θ-Al2O3 and β-Al2O3. Compared with the others, the β-Al2O3 content is the least. The MAO process can be divided into three periods, namely the common anodic oxidation stage, the stable MAO stage and the ceramic coatings destroyed stage. The exterior loose part of the ceramic coatings was destroyed badly in the last period which should be avoided during the MAO process.

Tic Particle Reinforced Iron Based Composite Coating by Submerged-Arc Welding Added Alloy Powder

TiC particle reinforced iron based composite coating were in situ synthesized on surface of Q235 steel by Submerged-arc Welding (SAW) using the mixture consisted of ferrotitanium, ferrochromium, iron and carbon powders. Microstructure of the coating was observed by scanning electron microscope（SEM）and X-ray diffraction(XRD). Microhardness was measured by microhardness tester. Results indicated that the fine TiC particles were formed by using SAW process and dispersed in the matrix. And the particles sizes were less than 2μm. Microstructure of coating consists of TiC particles, martensite and austenite. The microhardness of coating is HV575~HV617, which is about 3 times of that of the based metal.