Fe-based Coatings Research Articles

Effect of Cladding Fe-Based Coating on the Microstructure, Wear Resistance, and Dynamic Performance of CL60 Steel

Effect of Cladding Fe-Based Coating on the Microstructure, Wear Resistance, and Dynamic Performance of CL60 Steel

Fracture toughness and cavitation erosion behavior of Fe-based amorphous composite coatings with Ni-coated Al2O3 addition

Fe-based amorphous composite coatings were prepared on 304 stainless steel substrates using atmosphere plasma spraying (APS), aiming to investigate the effect of Ni-coated Al2O3 particles addition on fracture toughness and cavitation erosion behavior of Fe-based composite coatings. The microstructure, phase composition, elastic modulus, microhardness and fracture toughness of the coating were characterized using scanning electron microscopy with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), microhardness tester and nanoindentation. The cavitation erosion behavior of Fe-based coatings was investigated by ultrasonic vibration cavitation method. Fe-based amorphous composite coatings exhibit a characteristic lamellar microstructure and reveal the presence of amorphous phases along with α-(Fe, Cr), NiO, Ni and Al2O3 crystalline phases. When the content of Ni-coated Al2O3 in coating increases from 0 wt% to 3 wt%, there is slight deterioration in porosity from 3.64 % to 4.75 % and fracture toughness from 2.579 MPa·m1/2 to 2.392 MPa·m1/2, yet an increase in microhardness from 925.4 HV0.5 to 1090.3 HV0.5. The composite coating with 3 wt% Ni-coated Al2O3 demonstrates the peak cavitation resistance and its cumulative mass loss is significantly reduced by 36.4 % compared to the pure Fe-based coating. The cavitation erosion failure of Fe-based amorphous composite coatings is predominantly characterized by the brittle fracture mechanism. The fundamental process driving cavitation erosion damage involves the material peeling and coating delamination instigated by intense micro-jet impact and shock wave propagation. The proposed Fe-based amorphous composite coatings can be applied to improve the anti-cavitation performance of components in contact with high-speed fluids, such as ship propellers and centrifugal pump blades.

Wear and Corrosion Resistances of Arc-Sprayed FeCr Alloy and Fe-Based Coatings for Boiler Heat Exchanger Pipelines

Wear and Corrosion Resistances of Arc-Sprayed FeCr Alloy and Fe-Based Coatings for Boiler Heat Exchanger Pipelines

Enhancing Wear Resistance of Marine Steel with Fe Based Amorphous Coating Via HVOF Spraying

Mechanical friction in marine environments poses significant challenges, leading to resource depletion and energy consumption. Tribocorrosion, combining electrochemical corrosion and friction wear, jeopardizes metal components, necessitating robust protective measures. Despite minimal wear of marine equipment, even slight mass reductions can trigger catastrophic failures, resulting in substantial maintenance expenses. Steel structures in marine settings are vulnerable to corrosion from aggressive external and internal factors. ASTM AH36 steel, widely used in marine construction, faces wear challenges despite corrosion resistance, prompting the need for surface treatments and coatings to enhance longevity. Previous research emphasizes thermal spray methods, particularly HVOF-applied coatings, as eco-friendly solutions for improving wear resistance on marine steels. Fe-based coatings, characterized by improved hardness and corrosion resistance, offer promising solutions in abrasive marine environments, igniting fervent research efforts. This study conclusively demonstrates that AH36 steel samples coated with Fe-based amorphous layers exhibit substantially reduced wear rates.

Study of the effect of overlap rate on the failure form, microstructure and wear resistance of multilayer laser cladding on grey cast iron surfaces

Laser cladding is less used in the repair of cast iron parts. In this paper, multiple layers of austenitic stainless steel powders with different overlap rates were laser clad by the process of adding a transition layer to explore the feasibility of multilayer cladding of grey cast iron. The study results show that the higher cladding layers tends to cause cracking and warping of substrate, and the increased overlap rate of the Ni transition layer can effectively inhibit these failures. The wear mass of Fe-based coatings with 33.3%∼66.7% overlap was 1.00–2.68 mg. After wear, the Fe2p and Ni2p potentials were shifted, the intensity of the O1s characteristic peaks increased, and the wear oxidation increased wear quality loss.

Repair feasibility and performance enhancement analysis of Fe-based alloy coating on ductile iron surface by high-speed laser cladding

In this paper, high-speed laser cladding technology with a scanning speed of 40 mm/s was used to clad the ductile iron surface with the Fe-based alloy coating. The coatings' microstructure, element distribution, crystallographic structure, wear resistance, and corrosion resistance were investigated by using an optical microscope, SEM, XRD, friction and wear testing machine, super depth-of-field microscope, and electrochemical workstation. The results show that the microstructure of the coating is mainly γ-Fe solid solution and carbide eutectic structure. The phases of the coating are FCC phase (γ-Fe dominated), BCC phase, and carbide. The elemental distribution of the coating cross-section elements is uniform, and no quality obvious defects such as large gas pores and cracks are found. The coating mass loss was 60.0% and 47.1% of the substrate for different friction parameters and the more significant coating oxide build-up phenomenon with increased loading force. The self-corrosion rate of the coating was 0.006 g/m2·h, and the substrate was 0.042 g/m2·h; the maximum impedance value of the coating (1.34×104 Ω·cm2) was increased 20 times based on the substrate (619.2 Ω·cm2). In summary, Fe-based coatings with these process parameters can repair failed ductile iron parts and significantly extend their service life.

Surface Characteristics of Vacuum-Plasma-Sprayed Reinforced Stainless Steel Coatings with TiC Particles

Fe-based coatings reinforced with TiC particles exhibit outstanding properties and are widely recognized as highly promising coatings or components with superior performance. In the present study, composite materials using a powder mixture of AISI 316 stainless steel and TiC particles were deposited by vacuum plasma spraying onto a S235 low alloyed steel substrate. The coating and the base material were characterized in terms of microstructure and surface properties. The metallographic analysis of the deposited coating revealed the uniform distribution of the TiC into the stainless steel matrix. The results show that the presence of tungsten carbide particles improved the hardness and tribological properties of the composite coating compared with the S235 base material. The wear resistance of the coating was approximately seven times higher than that of the low alloyed steel substrate. The electrochemical corrosion resistance of the coating in chloride media was much higher than that of the base material.

Effects of scanning speed on the microstructure, hardness and corrosion properties of high-speed laser cladding Fe-based stainless coatings

Fe-based coatings have been prepared by utilizing laser cladding with the scanning speed ranging from 1.57 to 20.4 m/min. The microstructure and corrosion properties have been further investigated to evaluate the effects of scanning speed. The results show that, both coating's thickness and dilution rate gradually decrease with the increase of scanning speed. However, the deposition efficiency on the surface can be greatly improved by around 4 times. Under high scanning speed, the Fe-based coatings show the similar microstructure feature, comprising with dendrites and inter-dendritic structures. But the coating's microstructure can be significantly refined with the secondary dendritic arm spacing less than 1 μm. Furthermore, the gap of Cr concentration between the two structures can be effectively reduced, which shrinks the difference in corrosion resistance. On the other hand, the Fe-based coating's hardness gradually decreases resulting from the retained austenite and ferrite under high scanning speed. Compared to Q235 steel, the cladded Fe-based coatings show superior corrosion resistance with much higher corrosion potential and lower corrosion current density. Pitting dominates the corrosion forms of high-speed laser Fe-based coatings, which initially takes place on the boundaries of different structures. With the increase of scanning speed, the coating's corrosion resistance increases firstly and then decreases, and the coating cladded with the speed of 15.7 m/min shows the best corrosion resistance. Higher average Cr content and more uniform Cr distribution account for the better corrosion resistance. However, excessive microstructure refinement plays a negative role in the coating's corrosion resistance owing to more grain boundaries.

Microstructural, mechanical and high-temperature tribological performance of Fe-based fully amorphous and amorphous/crystalline coatings

In this research, fully amorphous and amorphous/crystalline (A/C) Fe-based coatings were explored for high-temperature tribological applications. The commercially available gas atomized feedstocks were sprayed using high velocity oxygen fuel (HVOF) processes. The microstructural, mechanical and tribological behaviour of the coatings were investigated and compared. The fully amorphous Fe-based amorphous coating exhibited higher wear resistance at 600 °C than room temperature (RT) with high thermal stability and performed superior to A/C coatings at both temperature conditions. Detailed analysis of worn surfaces demonstrated that fully amorphous coatings were dominated by abrasive wear and oxidative wear at RT and oxidative and adhesive wear at 600 °C, whereas A/C coating suffered abrasive, surface fatigue wear and minor oxidation at both RT and 600 °C. A thick oxide glaze layer formed onto the worn surface of fully amorphous coatings, which enhanced the high-temperature mechanical properties and prevented severe wear loss. The Fe-based amorphous coating exhibited superior wear resistance and retained its phase structure, which established it as a potential high-temperature protective coating for tribological applications.

Investigation of tensile fracture mechanism of Fe-based coatings deposited on different substrates by arc spraying

The adhesion strength of the coating to the substrate determines the service life and performance of components coated by thermal spraying. FeCrMoCBWNb coatings were deposited via arc spraying process to study the adhesion properties of the coatings on Q235 and 65Mn steel substrates. The adhesion properties and tensile fracture mechanisms of the coatings on different substrates were examined by the tensile bonding strength. The phase intensity and crystallinity of the coatings were studied by X-ray diffractometer (XRD). The microstructure and mechanical properties of the coatings were also characterized. The adhesion properties of the coatings depended on the substrates' mechanical properties. The tensile bonding strengths of the coating on Q235 and on 65Mn were 45.5 ± 5.4 MPa and 40.8 ± 1.4 MPa, respectively. The higher substrate roughness of the Q235 steel enhanced the mechanical interlocking of the coating particles to the substrate. The tensile fracture of the coatings comprised brittle and ductile fracture mechanisms.

Long-Term Stability of Ni–Sn–Fe-Based Coatings Prepared by Electrodeposition for the Oxygen Evolution Reaction

A coating comprising Ni, Sn, and Fe was deposited on a Ni mesh by cathodic polarization from a bath containing Ni2+, Sn2+, and Fe3+ salts in solution, and the oxygen evolution reaction properties of the thus obtained electrode were investigated. The lattice volume of the Ni–Sn–Fe-based coating was estimated to be 77.1 Å3, a much larger value than that (44.0 Å3) of the Ni–Fe-based coating obtained in the absence of Sn2+. The Ni–Sn–Fe-coated electrode manufactured by cathodic polarization at a current density of −120 mA cm−2 afforded a current density of 10 mA cm−2 at an overpotential of 276 mV in 1 M KOH. The said electrode’s Tafel slope was estimated to be 37 mV dec−1. When electrolyzed at constant current density (+50 mA cm−2 to +800 mA cm−2), it exhibited a stable potential for at least 162 h. The Ni–Sn–Fe-coated electrode was also used as the anode in a two-electrode cell (80 °C; 30 wt% KOH) and electrolyzed for 3 d. Evidence indicated a low cell voltage of 1.81 V at a current density of +600 mA cm−2, which is at an industrial level.

Evaluation of thermal shock failure mechanism of arc-sprayed Fe-based coatings deposited on different substrates

FeCrMoCBWNb coatings were fabricated on 65Mn and ASTM A238C steel via arc-spraying process to study the thermal shock behavior. To determine the influence of the substrate, the coatings' failure mechanisms were examined at 800 °C under different thermal cycles. The coating microstructure and mechanical properties were characterized. The crystallinity, peak intensity, mechanical properties, and surface roughness changed with the substrate type. The coating prepared on A238C steel presented improved resistance to thermal shock than the coating on 65Mn attributed to higher initial bonding strength. The mismatch of the mechanical properties between the coating and substrates influenced the adhesion and thermal shock properties of the coatings. The iron compounds and oxide layers at the interface and splat boundaries increased with the number of thermal cycles, resulting in internal cracking and de-bonding of the coatings.

Multi-layer laser cladding analysis and high-temperature oxidative wear behavior of cast iron with a low expansion coefficient

Laser cladding is among the critical processes for repairing and strengthening cast iron parts. To further improve the application of laser cladding on cast iron and provide a feasible technical approach for its surface cladding. In this paper, different alloy powders were clad on the surface of ductile cast iron and gray cast iron, commonly used cast iron materials in engine cylinder blocks. The multi-layer claddings of various powders on the cast iron surface were analyzed, and the oxidative wear behaviors of Fe-based coatings at high temperatures were discussed. The results show that the primary defects of the cladding layer were cracks and edge warping. The average stress relationship of each coating was: ∣dσNi∣<∣dσFe∣<∣dσCo∣, and the Ni-based layer internal stress was the minimum. The internal stress was mainly caused by the difference between the physical properties of the coating and the substrate, and cladding defects were easy to occur if the internal stress was too enormous. Ni-based coating with lower cladding stress can be a transition layer to avoid defects. The average wear of Fe-based coatings at room temperature, 100, 250, 500, and 750 °C was 2.83, 1.94, 4.46, 6.43 and 9.72 mg, respectively. The wear amount was the minimum at 100 °C. Temperature rising, the oxidation of the specimens intensified, and the wear amount increased.

Machine Hammer Peening and Its Effect on the Surface Integrity of Arc-Sprayed WC-W2C-FeCMnSi Coatings

With respect to post-processing techniques in the field of surface engineering, it was recently found that machine hammer peening (MHP) represents a promising approach to functionalizing thermally sprayed coatings as the MHP contributes to a compression of the coating, enabling the potential to reduce the coating porosity as well as the protruding peaks of the rough as-sprayed coating surface. The MHP also has the potential to induce compressive residual stresses in the coating surface, which can positively affect the mechanical and tribological properties. Arc-sprayed tungsten carbide-reinforced Fe-based coatings pose an appropriate candidate to counteract the wear of tribologically stressed surfaces. Due to the inherent process characteristics, however, these coatings are mostly characterized by a heterogeneous lamellar microstructure with residual porosity and interstratified with a certain amount of oxides, as well as the presence of tensile residual stresses. To adjust their microstructural and mechanical coating properties, the applicability of a subsequent MHP was evaluated in this study. Therefore, arc-sprayed WC-W2C reinforced FeCMnSi coatings are deposited using either argon or compressed air as atomization and shroud gas, providing different lamellar structures and oxide content. The effect of MHP on the surface integrity of the WC-W2C-FeCMnSi coating is investigated with respect to its porosity, lamellar structure, hardness, and residual stresses, which are known as relevant influencing factors on the performance of tribologically stressed components. It was found that the MHP leads to reduced porosity and lamella thickness as well as increased hardness due to strain hardening effects. Furthermore, it was demonstrated that the MHP leads to the introduction of compressive residual stresses, which contribute to a decline in tensile residual stresses in the near-surface area.

The effect of ultrasonic field on the microstructure and corrosion behavior of Fe-based amorphous coating applied to selective laser melting

This study was conducted to investigate the effect of the ultrasonic field on the preparation of amorphous/crystalline Fe-based coatings. For this purpose, Fe86.3Si 5.9B3.2Cr4.6 (wt%) powder was deposited on GTD-111 superalloy substrate with and without ultrasonic field by selective laser melting method. After coating, the corrosion behavior, microstructure, and hardness of the amorphous coating were investigated. The results showed that in conditions without ultrasonic vibration, the growth of grains starts in columnar form. At the same time, the use of an ultrasonic field inhibits columnar growth and creates equiaxed grains. In addition, the ultrasonic field increased the amorphous phase by 34.5%. This is attributed to the increased solidification rate caused by the cavitation effect. The experimental results of corrosion show that the self-corrosion current density of 6.83×10−7 A⋅cm2 is obtained due to the refinement of the microstructure and the increase of the amorphous phase. The wear results showed that the increase in the amorphous phase, as well as the decrease in the grain size, reduction in the grain ratio, and the increase in the tendency to equiaxed grains when using the ultrasonic field, reduce the coefficient of friction by 97%.

Optimizing Parameters of Arc-Sprayed Fe-Based Coatings Using the Response Surface Methodology

Optimizing Parameters of Arc-Sprayed Fe-Based Coatings Using the Response Surface Methodology

Evaluation of corrosion and wear performance of Fe-based coating and hastelloy C276 in H2S environment on 304 stainless steel substrate

In order to improve the performance of 304 stainless steel for use in oil and gas field applications and broaden its applicability, Fe-based coatings with small amounts of amorphous structures were prepared by high-velocity oxygen-fuel spraying onto stainless steel substrates. The wear resistance and hydrogen sulfide corrosion resistance of the coatings were tested and compared to the preferred corrosion resistance of Hastelloy C276 coatings. Samples with two kinds of coatings were subjected to 720 h of corrosion in a 40 °C H2S solution. The effects of corrosion on the microstructure and phase composition of the sprayed coatings were analyzed using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The mechanical properties of the materials were characterized using nano-indentation, a friction-abrasion testing machine, and confocal laser microscopy. The results showed that both coatings provided excellent resistance to H2S corrosion (0.14, 0.15 mm/y), but the Fe-based coating was more effective at enhancing the hardness (twice as much as C276 coating), Young's modulus, and wear resistance of the stainless steel. Given its higher wear resistance and lower cost, the Fe-based coating was concluded to be more effective in protecting 304 stainless steel for use in oil and gas applications.

Effect of Laser Remelting of Fe-Based Thermally Sprayed Coating on AZ91 Magnesium Alloy on Its Structural and Tribological Properties

An Fe-based coating was thermally sprayed onto the surface of AZ91 magnesium alloy via the High-Velocity-Oxygen-Fuel (HVOF) method. The thermally sprayed coating with a thickness of 530 ± 25 µm and a porosity of 0.7 ± 0.1% did not show any macrostructural defects and did not cause any degradation of the AZ91 alloy. Laser remelting of the surface layer of the sprayed coating resulted in the recrystallization of the structure and the disappearance of presented pores, splat boundaries, and other defects. This led to an increase in the hardness of the remelted layer from the original 535 ± 20 HV0.3 up to 625 ± 5 HV0.3. However, during the laser remelting at a laser power of 1000 W, stress cracking in the coating occurred. The tribological properties were evaluated by the ball-on-plate method under dry conditions. Compared to the uncoated AZ91 magnesium alloy, a higher value of friction coefficient (COF) was measured for the as-sprayed coating. However, there was a decrease in wear rate and weight loss. The remelting of the surface layer of the as-sprayed coating led to a further decrease in the wear rate and weight loss. Based on the obtained data, it has been shown that the application of laser-remelted thermally sprayed Fe-based coatings on AZ91 Mg alloy improves hardness and tribological properties compared to bare Mg alloy and as-sprayed Fe-based coatings.

Effect of Grit-Blasting Pretreatment on the Bond Strength of Arc-Sprayed Fe-Based Coating

Effect of Grit-Blasting Pretreatment on the Bond Strength of Arc-Sprayed Fe-Based Coating

Microstructure and Corrosion Behavior of Fe-Based Austenite-Containing Composite Coatings Using Supersonic Plasma Spraying

The Fe-based austenite-containing composite coatings with various contents (3 vol.%, 6 vol.%, 9 vol.%, 12 vol.%) of austenite powder additions were created by supersonic plasma spraying on 45 steel substrates. The microstructure, phase composition, microhardness, and porosity of the composite coatings were examed. Moreover, special attention was paid to the effect of austenite powder on the corrosion resistance of the austenite-containing composite coatings. The results found that the addition of austenite powders could significantly improve the corrosion resistance of Fe-based coatings, which is mainly due to three correlated phenomena caused by the austenite particles. First, austenite particles significantly reduce the porosity of the austenite-containing composite coatings and form a denser coating structure due to their low melting point and good chemical compatibility with the Fe-based alloy. Further, austenite particles help to refine the grains and increase the grain boundary density. Last but not least, austenite particles help to generate more diffusely distributed second phases in the coating, improving the chemical homogeneity and hardness of the coating.