Fe-based Amorphous Coatings Research Articles

An Experimental Study on the Properties of Fe-Based Amorphous Composite Coatings Prepared by Different Processes

Fe-based amorphous composite coatings were deposited on the surface of ASTM-1020 steel plate by different technologies: arc spraying, laser remelting, TIG remelting (with and without water cooling). The microstructure, phase structure and micro-hardness were characterized by using a combination of SEM, XRD and Vickers hardness tester. It shows that the coating prepared by arc spraying presents typical lamellar structure and poor adherence to the substrate. After the remelting treatment, the coating quality is significantly improved by decreasing structure defects such as cracks and pores; the interface shows the metallurgical bonding. The dendritic crystals could be obtained within all the remelted coatings with different appearances. The microstructures of TIG remelted coatings show much more regular and have obvious orientation, which cannot be seen in laser remelted coating. However, the average grain size of the laser remelted coating is much smaller than that of TIG remelted coatings. The micro-hardness values of all of the deposited coatings are much higher than that of the substrate, and the coating prepared by laser remelting shows the highest hardness.

Microstructure and Wear Resistance of Fe-Based Multi-Layers Amorphous Composite Coatings by Tungsten Inert Gas Cladding

Microstructure and Wear Resistance of Fe-Based Multi-Layers Amorphous Composite Coatings by Tungsten Inert Gas Cladding

Phase Transformation, Microstructure and Hardness of Electrodeposited Fe-Based Amorphous Coatings

Fe-based amorphous coatings have many excellent performances, such as good corrosion resistance, high hardness, satisfactory magnetism, etc. In this paper, Fe-P amorphous coatings were prepared by electrodeposition method, and the phase transformation, microstructure, and hardness of the coatings heated at different heat-treatment temperature were investigated. The results show that Fe-P amorphous coatings begin to crystallize when heated at 300°C, the α-Fe(P) solid solution appears when heated at 330°C, and FexP(X=1,2,3) compounds separate out from the solid solution when heat-treatment temperature is up to 370°C. During the process of heat-treatment, hardness of the Fe-P coating increases as the reinforcement result of solid solution and dispersed phase in the coatings, and the hardness reaches the maximum 1100 HV at 370°C. When heat-treatment temperature is higher than 460°C, dispersed phase in the coatings will grow up, which is called Ostwald Coarsening Phenomenon, and hardness of the coating decreases quickly.

A Hard and Thick Fe-Based Amorphous Composite Coating

A thick Fe-based amorphous and nanocrystalline composite coating was prepared by in-situ tungsten inert gas (TIG) cladding method. The results show that the cladding coating mainly consists of amorphous phase and nanocrystalline grains. The microstructure study shows that the Fe-based composite coatings have unique microstructure including nano-sized grains surrounded by nano-scale amorphous shell layer (encapsulated structure) and the homogeneously distributed dendrites/cellular crystals. The unique microstructure gives rise to the superior micro-hardness and wear resistance of the coating. The Fe-based coatings have great potential as promising wear-resistance structural materials used in electric power and cement industry.

不锈钢表面激光熔覆铁基非晶涂层研究

不锈钢表面激光熔覆铁基非晶涂层研究

Study of structure and corrosion resistance of Fe-based amorphous coatings prepared by HVAF and HVOF

Fe-based amorphous coatings with a composition of Fe 49.7Cr 18Mn 1.9Mo 7.4W 1.6B 15.2C 3.8Si 2.4 have been prepared on a mild steel substrate by High velocity air fuel (HVAF) and High velocity oxygen fuel (HVOF) processes. The microstructure and corrosion resistance in 3.5 wt.% NaCl solution of the coatings prepared by the two processes were comparatively studied. It was found that the two coatings exhibit dense structure with the porosity of 0.4% and compact bonding with the substrate. However, HVOF coating contains higher oxygen content than HVAF coating, resulting from the formation of significant oxide contours between the partially melted particles in HVOF process. Electrochemical polarization tests and electrochemical impedance spectroscopy (EIS) analysis indicate that the HVAF coating has better corrosion resistance than the HVOF coating. The preferential corrosion along the oxide contours thus providing efficient diffusion channels for electrolyte accounts for the poor corrosion resistance in HVOF coating. The present results demonstrate that HVAF with less cost can be a promising spray process to fabricate the Fe-based amorphous coating for industrial applications.

Microstructure and Electrochemical Behavior of Fe-Based Amorphous Metallic Coatings Fabricated by Atmospheric Plasma Spraying

A Fe48Cr15Mo14C15B6Y2 alloy with high glass forming ability (GFA) was selected to prepare amorphous metallic coatings by atmospheric plasma spraying (APS). The as-deposited coatings present a dense layered structure and low porosity. Microstructural studies show that some nanocrystals and a fraction of yttrium oxides formed during spraying, which induced the amorphous fraction of the coatings decreasing to 69% compared with amorphous alloy ribbons of the same component. High thermal stability enables the amorphous coatings to work below 910 K without crystallization. The results of electrochemical measurement show that the coatings exhibit extremely wide passive region and relatively low passive current density in 3.5% NaCl and 1 mol/L HCl solutions, which illustrate their superior ability to resist localized corrosion. Moreover, the corrosion behavior of the amorphous coatings in 1 mol/L H2SO4 solution is similar to their performance under conditions containing chloride ions, which manifests their flexible and extensive ability to withstand aggressive environments.

Fabrication of Fe-Based Amorphous Composite Coatings by Electrothermal Explosion Spraying on Aluminum Substrate

In order to improve the surface properties of the aluminum alloy, an amorphous composite coating was prepared on the surface of the aluminum alloy substrate by electrothermal explosion spraying with fully amorphous Fe-Si-B ribbons. The microstructure, phase structure and micro-hardness of the coating were characterized by SEM, XRD and Vickers hardness tester. The results show that the composite coating is composed of amorphous phase and nanocrystal phase. The coating has dense structure and low porosity. It has not been seen rough laminar microstructure that is frequently obtained by other thermal spray techniques. The amorphous composite coatings with different thickness present higher hardness and show good mechanical properties.

Wear Behavior of Fe-Based Coating Fabricated by Plasma Thermal Spraying

The Fe-based amorphous coatings were prepared by Air plasma thermal spraying. X-ray diffraction results show that the coating fabricated at current of 300A has an amorphous structure. The amorphous nanocrystalline composite coatings were obtained at current more than 300A. The friction and wear properties of the coatings were investigated in Ml-10 friction and wear tester at dry friction condition. The results show that the amorphous content is the main influencing factors to wear resistance of coating. The density of coating is another reason to affect the wear resistance of amorphous nanocrystalline composite coating.

Microstructure and Wear Resistance of Fe-Based Amorphous Metallic Coatings Prepared by HVOF Thermal Spraying

Amorphous metallic coatings with a composition of Fe48Cr15Mo14C15B6Y2 were fabricated by means of high velocity oxygen fuel (HVOF) thermal spraying process. The microstructure and wear performance of the coatings were characterized simultaneously in this article. It is found that the coatings present a dense layered structure with the porosity below 1.5%. The coatings primarily consist of amorphous matrix and some precipitated nanocrystals, though a fraction of Fe-rich phases and oxide stringers also formed during deposited process. High thermal stability enables the amorphous coatings to work below 920 K temperature without crystallization. Depending on the structural advantage, the amorphous coatings exhibit high average microhardness of 997.3 HV0.2, and excellent wear resistance during dry frictional wear process. The dominant wear mechanism of amorphous coating under this condition is fatigue wear, leading to partial or entire flaking off of the lamellae. In addition, the appearance of oxidative wear accelerates the failure of fatigue wear.

Fe-Based Micro- and Nanocomposite Coatings Produced by Amorphous Alloy Crystallization Based on Electrospark Deposition

The aim of this paper is to explore the possibility of a novel surface technique for Fe-based amorphous and micro-nano composite coatings. A kind of iron based amorphous and micro/nano-crystalline alloy powder which contains Fe, Ni, Cr, W, Mo, B, Si, C etc. was first prepared by mechanical alloying method. Iron based amorphous alloy coatings were then deposited on nodular cast iron substrate by electro-spark deposition using electrode materials with the ball-milling iron based alloy and SiC mixed powders. Annealing crystallization treatment of the Fe-based amorphous alloy coatings was conducted at last. The microstructure and surface morphology of the coating were analyzed by optical microscopy (OM) and scanning electron microscopy (SEM), the amorphous and crystal configuration were confirmed with an X-ray diffractometer (XRD), the microhardness was measured with a micro-sclerometer. The experimental results show that the Fe-based composite coatings are composed of Fe-based amorphous alloy matrix and dispersion strengthened micro- and nanocrystalline particles. The coatings of about 60 m in thickness are uniform, dense and metallurgically bonded to the substrate with high microhardness of about 880 (HV100, 15 S), implying a much improved wear resistance on surface of cast iron.

Formation of Fe-Based Amorphous Coating Films by Thermal Spraying Technique

Some amorphous Fe-Cr-P-C coating films having high hardness and high corrosion resistance have been produced by a newly developed thermal spraying technique. In order to control the temperatures of the powder particles in the flame spray and the substrate, a newly developed cylindrical nozzle, with external cooling nitrogen gas, was mounted to the front end of the thermal spraying gun. Fe 70 Cr 10 P 13 C 7 films with various external cooling gas velocities between 20m/s and 40m/s exhibited entire amorphous structure without oxides and/or unmelted particles. Corrosion-resistance of the films was observed in immersion tests using various corrosive liquids. An amorphous film was formed on the surface of the shaft sleeve of the slurry pump by using the cylindrical nozzle. This shaft sleeve was installed in the slurry pump of chemical fertilizer maker's production line and the life test was done under the real operation condition for two months.

Formation and corrosion behavior of Fe-based amorphous metallic coatings prepared by detonation gun spraying

Amorphous metallic coatings with a composition of Fe 48Cr 15Mo 14C 15B 6Y 2 were prepared by detonation gun spraying process. Microstructural studies show that the coatings present a densely layered structure typical of thermally sprayed deposits with the porosity below 2%. Both crystallization and oxidation occurred obviously during spraying process, so that the amorphous fraction of the coatings decreased to 54% compared with fully amorphous alloy ribbons of the same component. Corrosion behavior of the amorphous coatings was investigated by electrochemical measurement. The results show that the coatings exhibit extremely wide passive region and low passive current density in 3.5% NaCl (mass fraction) and 1 mol/L HCl solutions, which illustrates excellent ability to resist localized corrosion.

Formation and corrosion behavior of Fe-based amorphous metallic coatings by HVOF thermal spraying

Amorphous coatings with a composition of Fe 48Cr 15Mo 14C 15B 6Y 2 were prepared by means of high velocity oxygen fuel (HVOF) thermal spraying under different conditions. Microstructural studies show that the coatings present dense layered structure and low porosity with a fraction of nanocrystals precipitated. The porosity and amorphous fraction of the coatings decrease as the kerosene and oxygen flow increase within the parameter range examined. Corrosion behavior of the amorphous coatings was investigated by electrochemical measurement. The results show that the coatings are spontaneously passivated with wide passive region and low passive current density in 3.5% NaCl, 1 N HCl and 1 N H 2SO 4 solutions, and exhibit an excellent ability to resist localized corrosion. However, the corrosion resistance of the coatings decreases in 1 N NaOH solution with lower transpassive potential and passive region. In addition, the optimal spraying parameter improves the corrosion resistance of the amorphous coatings obviously due to the proper proportion of porosity and amorphous fraction.

Microstructure and Wear Behavior of Thermally Sprayed Fe-Based Amorphous Coating

In this study, microstructure and wear behavior of thermally sprayed Fe-based alloy coatings were investigated. Fe-based alloy coatings were formed on a carbon steel substrate and then heat-treated at temperature of 700 oC for 20 minutes. Dry sliding wear tests were performed using the sliding speeds of 0.4 and 0.8 m/s, the applied loads of 3 and 6 N. Microstructure and wear behavior of as-sprayed and heat-treated Fe-based amorphous coatings were studied using a scanning electron microscope(SEM), transmission electron microscopy(TEM) and X-ray diffraction(XRD).

Synthesis of Fe-based amorphous composite coatings with low purity materials by laser cladding

Amorphous composite coatings Fe 38Ni 30− X Si 16B 14V 2M X ( X = 0, 1, 2) (M contains Al, Ti, Mo, and C) were prepared with low purity of raw materials by laser cladding. X-ray diffraction and transmission electron microscopy results show that the coating have an amorphous structure with a few crystalline phase on it. The amorphous phase is the primary phase. The glass forming ability as well as the microhardness of the Fe-based alloy made from low purity raw materials can be much enhanced by adding small amount of multi-components. However, the elements addition has its optimal quantity. When X is equal to 1, the microstructure of the coating contains 97.93% amorphous phase and 2.07% crystalline phase on it. As a result, the microhardness of the coating reaches maximum. With further increasing of the additions, the amorphous phase in the coating lessens instead of augment and the crystalline phase begins to accumulate, which result in the decrease of the microhardness.

Electro-spark deposition of Fe-based amorphous alloy coatings

A simple and effective surface coating technique, electro-spark deposition (ESD), has been used to produce amorphous alloy coatings. Fe–Cr–Mo–Gd–C–B amorphous alloy rods produced by copper mould casting were used as electrode to produce coatings onto 304 stainless steel substrate. Classical X-ray diffraction (XRD), glancing angle XRD (GAXRD), and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis indicate that the coatings have an average thickness of ∼ 30 μm, show an amorphous structure, and are metallurgically bonded to the substrate. Microhardness tests showed that the coating layer has a high hardness of 1542 kg/mm 2, implying a much improved wear resistance on surface of stainless steels.

Fe-based thick amorphous-alloy coating by laser cladding

New thick Fe-based amorphous alloy coatings have been synthesized by laser surface cladding, with the nominal composition of Fe 57Co 8Ni 8Zr 10Si 4B 13 (at.%). The supercooled liquid region, Δ T x, defined by the difference between the glass transition temperature ( T g) and the onset temperature of crystallization ( T x) was as large as 62 K and T g was 821 K. The high thermal stability of the supercooled liquid enabled the synthesis of a coating with maximum thickness of 1.2 mm. The amorphous alloy coating had a high Vickers hardness of 1270 and good corrosion resistance.