High Temperature Corrosion Resistance Research Articles

Effects of Mn content on austenite stability and mechanical properties of low Ni alumina-forming austenitic heat-resistant steel: a first-principles study

Low Ni alumina-forming austenitic (AFA) heat-resistant steel is an advanced high-temperature stainless steel with reduced cost, good machinability, high-temperature creep strength, and high-temperature corrosion resistance. Using the First-principles approach, this study examined the effect of Mn content on austenite stability and mechanical properties at the atomic level. Adding Mn to low Ni-AFA steel increases the unit cell volume with an accompanying increase in the absolute value of formation energy; the austenite formed more easily. The austenitic matrix binding energy decreases and remains negative, indicating austenite stability. As the Mn content increases from 3.2 to 12.8 wt%, the system's bulk modulus (B) rises significantly, and the shear modulus (G) falls. In addition, the system's strength and hardness decrease, and the Poisson ratio of the austenite matrix increases with improved elasticity; the system has excellent plasticity with an increase in the B/G. For the Fe22–Cr5–Ni3–Al2 system, with the increase of Mn content, the electron density distribution between the atoms is relatively uniform, and the electrons around the Mn atoms are slightly sparse, which will slightly reduce the structural stability of the matrix. The experiment demonstrated the matrix maintains the austenitic structure when adding 3.2–12.8 wt% Mn elements to low Ni-AFA steel. At an Mn content of 8 wt%, the overall mechanical properties of the high-Mn AFA steel are optimal, with a tensile strength of 581.64 MPa, a hardness of 186.17 HV, and an elongation of 39%.

Fabrication of Ni-Co film for enhancing the high-temperature corrosion resistance of interconnects in solid oxide fuel cells (SOFCs)

ABSTRACT Low-cost Ni-Co alloy coating was performed by electroplating technique to improve the high-temperature corrosion resistance of stainless steel interconnects in solid oxide fuel cells (SOFCs). The effect of plating on the surface morphology, microstructure and composition of Ni-Co alloys was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and atomic force microscopy (AFM). The Ni-Co coatings were fabricated at thickness of around two microns and compared at different Ni-Co molar ratios. Corrosion performance of Ni-Co coating was evaluated in a muffle furnace under ambient atmosphere at 800℃ for 110 h. Co2NiO4 spinel oxides and Cr2O3 were found on the Ni-Co coated samples after the oxidation test. Results indicated that steel substrate corrosion protection improved with a low parabolic rate constant of 20 times after Ni-Co alloy electrodeposition coating. A smooth coating layer containing Co2NiO4 oxide with fewer defects promoted high oxidation resistance of the steel samples.

Surface defect detection of CFRP materials based on infrared thermography and Attention U-Net algorithm

ABSTRACT Carbon fiber reinforced polymer (CFRP) materials have been widely used in aerospace and other fields because of their excellent properties such as high temperature resistance and corrosion resistance, so the nondestructive inspection technology for CFRP materials has become a hot research topic. In this paper, we propose a method based on infrared thermography and Attention U-Net algorithm to characterize the defect shape of CFRP material surface. Firstly, the CFRP surface is scanned by a line laser and the trend of its temperature distribution is recorded using an infrared thermography camera. Subsequently, temperature analysis and entropy value of image information are calculated for individual defect image blocks in order to select images with clear defect contours. Next, the Attention U-Net is used to segment the defect in the image blocks, and the defect shape is characterization. By calculating the evaluation indexes of image segmentation, the method in this paper can achieve 99.57% accuracy, 97.06% recall, 96.63% precision, and the processing time for a single image is 0.13s. Finally, the algorithm of this paper is compared with other algorithms to verify the advantages of this research in the task of detecting surface defects in CFRP materials with fast and high accuracy.

Characterization of Iron Aluminide Diffusion Coatings Obtained after Friction Surfacing

Iron aluminides are considered as candidate materials for high temperature applications for their excellent high temperature corrosion and oxidation resistance. In the present work, iron-aluminide coatings were developed by friction surfacing (6351 aluminum alloy deposited on a low-carbon steel substrate) followed by a diffusion heat treatment. The initial coatings were found to be geometrically homogenous and adhered well to the steel substrate. The heat treatment process was carried out at 550 °C for 48, 72 and 96 h and the resulting coatings were characterized in terms of microstructure, chemical composition, hardness distribution and phase composition. After heat treatment, the coating/substrate interface morphology was modified and presented patterns typical of Fe-Al intermetallic formation, as well as a substantial increase in hardness (>900 HV) relative to the initial as-deposited condition. With the diffusion treatment, initially Fe2Al5 was found to develop in the coatings, which was converted into FeAl2 after longer exposures.

Effects of deposition temperature on the microstructure, mechanical properties, high temperature corrosion and oxidation properties of AlCrNbTiZr high entropy alloy coatings

The AlCrNbTiZr high-entropy alloy (HEA) coatings with different deposition temperatures were prepared on Zr-4 substrate by magnetron sputtering. The effects of the deposition temperature on microstructure, mechanical properties, surface wettability, high temperature corrosion and oxidation resistance of coatings were systematically studied. The results show that the thickness of coating decreases first and then increases with the increase of deposition temperature. The coatings deposited at all temperatures is amorphous with BCC nanocrystalline domains, and the coating surface is hydrophobic. The room temperature (RT) deposition coatings have a high hardness of 25.41GPa, a good adhesion of 50 N and corrosion resistance compared with the coating at other deposition temperatures. The coating at RT deposited still has the ability to protect the substrate Zr-4 after the 1200 °C steam oxidation for 30 min. In addition, the corresponding steam oxidation mechanism is discussed in detail.

High-Temperature Corrosion of Flame-Sprayed Power Boiler Components with Nickel Alloy Powders

The development trends in the energy sector clearly indicate an increase in the share of biomass and alternative fuels fed for combustion in power boilers, which results in the imposition of many unfavourable factors and a demanding working environment. During the operation of the energy system, this means a sharp increase in corrosion of the gas-tight pipe walls and coils by the destructive action of chlorine and sulphur. Implementing advanced surface protection in addition to the selection of materials of better quality and resistance to difficult working conditions would significantly reduce their wear by high temperature corrosion. Thermally sprayed coatings offer a great opportunity to protect machine components and energy systems against corrosion, erosion, impact load and abrasive wear. This article presents the test results of high-temperature corrosion resistance of coatings made with Ni-Cr-B-Si and Ni-B-Si alloy powders on a boiler steel substrate. Samples with sprayed coatings were exposed to an atmosphere with a composition of N2 + 9% O2 + 0.08% SO2 + 0.15% HCl at 800 °C for 250, 500, 750 and 1000 h. Tests results of coatings made of Ni-Cr-B-Si alloys subjected to the influence of a corrosive environment showed the formation of a layer of scale on the surface, composed mainly of Cr2O3 oxide, which was a passive layer, reducing the rate of corrosion. Coatings sprayed with Ni-B-Si alloys showed significantly lower corrosion resistance. It was found that the developed technology of subsonic flame spraying with powders of the Ni-Cr-B-Si type allows the production of coatings compliant with the requirements of the energy industry, which allows their use as anti-corrosion protection on boiler elements intended for waste disposal and biomass combustion.

Permeability and corrosion resistance of porous SiOC‐bonded SiC ceramics prepared by the preceramic polymer

AbstractPorous SiC ceramics have been used in high temperature flue gas filtration fields because of their excellent properties such as high strength, high temperature resistance, corrosion resistance, and long service time. This work reports the porous SiOC‐bonded SiC ceramics prepared at low temperature. The properties of porous SiC ceramics were first investigated with silicone resin content from 10 to 25 wt%, and then the effects of different pore‐forming agent contents on the behaviors of porous SiC ceramics were discussed by adjusting poly (methyl methacrylate) PMMA microbeads from 5 to 20 wt%. The prepared porous SiC ceramics showed apparent porosity from 17.3% to 57.7%, compressive strength from 6 to 216 MPa, and Darcy permeability k1 ranging from 7.02 × 10−14 to 1.45 × 10−12 m2. The corrosion behavior of porous SiC ceramics was investigated in acidic and alkaline media. The porous SiC ceramics showed better corrosion resistance in acidic solutions.

Validation of Cr6Fe18Mo in tribaloy T-800 coating fabricated by induction heating assisted laser cladding

Due to excellent performance of high-temperature wear and corrosion resistance, Tribaloy 800 (T800) alloy has been used in steel and petrochemical industry. Most scholars believe that it is Laves phase (Co3Mo2Si) that leads to high crack sensitivity of T-800 alloy. However, the formation of Laves phase is impossible under conditions where there is a tendency of phase separation. In this study, the phases composition of T-800 coatings fabricated by induction heating assisted laser cladding (IHLC) is discussed. Results show that T-800 coatings prepared by IHLC are consist of Cr6Fe18Mo5 and γ-Co supersaturated solid solution with many lattice defects. With the increase of preheating temperature, the fraction of Cr6Fe18Mo5 phase can be increased to be 51.19%, due to sufficient Fe element and maintaining time of temperature above 700 °C. The fraction of γ-Co with lattice defects and residual tensile stress in coating can be decreased with the increase of preheating temperature, which lead to a crack-free T-800 coating.

Effect of Mo Content on Microstructure and Mechanical Properties of Laser Melting Deposited Inconel 690 Alloy

Inconel 690 alloy is widely used in nuclear power, petrochemical, aerospace, and other fields due to its excellent high-temperature mechanical properties and corrosion resistance. The Inconel 690 alloy with different Mo content was fabricated by laser melting deposition (LMD). The effects of Mo content on the microstructure and mechanical properties were investigated. The microstructure of as-deposited Inconel 690 is composed of columnar dendrites grown epitaxially, and M23C6 carbides are precipitated in the grain boundaries. With the increase of Mo content, the amount of precipitated carbide increases gradually. At the same time, the grain boundary becomes convoluted. The tensile test at room temperature shows that the high Mo content in the as-deposited Inconel 690 increases the ultimate strength but decreases the ductility. Compared with low Mo content, the alloy with high Mo deposition has better mechanical properties. The present study provides a new method to achieve the preparation of Inconel 690 alloy with excellent integrated mechanical properties.

Ice-templated assembly strategy to construct oriented porous Ti3SiC2 ceramics for thermal management and electromagnetic interference shielding in harsh thermal environments

Given the electromagnetic interference (EMI) and heat aggregation issue faced by electronic components, an urgent need exists to integrate EMI shielding and thermal conductivity in one material. Herein, a novel lightweight porous Ti3SiC2 ceramic with ordered structural arrangement was fabricated by using budget-friendly raw materials through ice template design and in-situ reaction synthesis. Leveraging the excellent conductivity and thermal conductivity of Ti3SiC2, a dual-functional advanced material with efficient EMI shielding and thermal management capabilities was obtained. At room temperature, porous Ti3SiC2 ceramics can achieve a shielding effectiveness of 35.44 dB and a thermal conductivity of 12.17 W/mK, with performance that can be tuned by porosity. In further, the porous Ti3SiC2 ceramic can work stably in thermal environments from room temperature to 700 °C or in corrosive environments rich in acid, alkali, and salts due to its excellent high temperature oxidation resistance and corrosion resistance. In view of the dual-functional characteristics and the stability of operation in harsh thermal environments, ordered porous Ti3SiC2 ceramics are promising for modern maritime and aerospace applications.

Optimization of material and process parameters for plasma transferred arc hard facing for high temperature applications

The authors in this research paper have investigated the process of hardfacing, which is a well-established manufacturing process for increasing the durability of industrial components, which are subjected to extreme wear, erosion, abrasion. The objective of this study is to establish a scientific methodology to select the most suitable combinations of materials as base-deposition materials for hardfacing, specifically focusing on Nickel-based and Cobalt-based materials. In order to make an informed decision, multi-criteria decision-making method known as “Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS)” is used. This technique permits to deal with wide range of important factors, such as the materials' high-temperature resistance, wear resistance, and corrosion resistance, among others. The paper discusses a step-by-step approach to selecting the best alternative material for hardfacing by considering eight different criteria and assigning preferences to each of the available materials. The results of this methodology suggested that Stellite-6 based cobalt-based alloy is best suitable for AISI 304 grade austenitic stainless steel materials used for high temperature applications.In addition, the paper also studies the effects of various welding parameters on the hardfacing process. This includes parameters such as welding current, welding speed, powder feed rate and the type of shielding gas used. The significance of each parameter is also studied, and the results of these investigations are discussed in detail. Overall, this research paper provides a comprehensive overview of the hardfacing process and the materials and techniques that are best suited for it, making it valuable resource for professionals and researchers in the field.

Effect of Aluminizing on the Fatigue and High-Temperature Corrosion Resistance of Inconel 740 Nickel Alloy

The fatigue response and high-temperature corrosion resistance of Inconel 740 nickel alloy in its as-received state, and the same material with aluminized surface layer, were investigated. The aluminized layer was applied by using the chemical vapor deposition process with the participation of AlCl3 vapors under a hydrogen protective atmosphere at a temperature of 1040°C for 8 h and internal pressure of 150 hPa. The microstructure of the aluminized layer was characterized through scanning electron microscopy and x-ray energy dispersive spectroscopy analysis. It was found that Inconel 740 with an aluminized surface exhibited an improved hardness and fatigue response of 100 MPa in the whole range of stress amplitudes from 350 MPa to 650 MPa. Additionally, the application of the aluminization process enhanced service life as well as the corrosion resistance of the alloy in question and effectively protected it against high-temperature corrosion.

Elevated corrosion resistance and improved magnetic properties of sintered Nd-Fe-B magnets via the infiltration of DyCr film

The low coercivity at high temperature and poor corrosion resistance limit the application field of Nd-Fe-B magnets. In this work, a DyCr film was prepared on the surface of Nd-Fe-B magnet through magnetron sputtering, and then subjected to grain boundary diffusion (GBD) to improve magnetic properties and enhance corrosion resistance. The results show that the residual Cr-rich film exists on the surface of NdFeB magnets, acting as a protective coating to enhance the corrosion resistance, which is evidenced by the weight loss experiment and scanning electron microscopy (SEM) image. Moreover, Cr element in the grain boundary phase increase the electrochemical potential from − 0.985 to − 0.733 V, which is also beneficial in improving corrosion resistance. Transmission electron microscope (TEM) analysis confirmed that the crystal structure of intergranular phase remained unchanged after diffusion, i.e. BCC-RE2O3 (RE=Rare Earth) phase. The coercivity was improved significantly, obtaining an increment of 19.4% comparing to that of initial magnet, which is attributed to the formed Dy-rich shell with high magnetocrystalline anisotropy field and the improved distribution of grain boundary phase. This suggests that it is feasible to fabricate high coercivity magnets and strong corrosion resistance only through grain boundary diffusion, which is expected to further shorten the processing flow of Nd-Fe-B magnets.

Combination of direct ink writing and reaction bonded for rapid fabrication of SiCw/SiC composites

Silicon carbide ceramic matrix composites are widely used in aerospace field due to their advantages of high temperature resistance, high strength and corrosion resistance. However, its application is greatly limited because of the difficulty in preparing complex shape structures by traditional machining methods. Here, a new strategy for preparing SiC w /SiC complex structure by combining direct ink writing with reaction bonding is proposed. A water-based slurry consisting of silicon carbide, carbon powder and silicon carbide whisker was developed. The influence laws of C content and SiC w content in slurry on sintering properties of direct-written samples were studied. The reaction bonding mechanism and whisker reinforcing and toughening mechanism were analyzed by means of microstructure and phase composition. The results show that the slurry exhibits shear thinning behavior with stress yield point, and its flow behavior and plasticity meet the requirements of direct writing. When the carbon content is 6.4 wt%, the maximum flexural strength is 239.3 MPa. When 15 wt% SiC w was added, the flexural strength of the composite reached 301.6 MPa, and when 20 wt% SiC w was added, the fracture toughness of the composite reached 4.02 MPa m 1/2 , which was increased by 26% and 18% compared with single-phase SiC, respectively. The reinforcing and toughening mechanisms of the whiskers mainly include whisker pullout, crack deflection and whisker bridging. After direct ink writing and reaction bonded, the whole process shows good near net forming ability. 3D printed SiC w /SiC composites have great application prospects in aerospace field.

A review on Ti-based metal matrix composite coatings

Lightweight high-strength Ti-based metal matrix composites (Ti-based MMCs) have a multitude of application applications, e.g., biomedical engineering, aerospace, and automotive, due to their good sustainability, high specific strength/stiffness, high elevated temperature strength, high wear, and corrosion resistance. Although there are metal matrix composite coatings comprised of polymers, composite, and ceramics materials, the paper primarily focuses on titanium-based composite coatings. This review also discusses the different coating techniques including electrodeposition, thermal spray, plasma spray, vapor deposition, and laser cladding to achieve high hardness and roughness, wear resistance and corrosion resistance. Totally, we attempt to bring out Ti based materials scenario for its current applications.

Recovery of samarium(III) and cobalt(II) in synthetic nitric acid solutions using carboxyl functionalized ionic liquids and application to recycling SmCo permanent magnets

Samarium (Sm), as one of the lanthanide elements, has a broad application prospect in the synthesis of samarium cobalt permanent magnet materials with high temperature stability, corrosion resistance and oxidation resistance. Due to the unlimited demand of Sm(III), recycling of Sm(III) waste is an effective method to balance economy and supply. In this paper, three novel morpholine carboxylic acid ionic liquids (ILs) were rationally designed and successfully synthesized for the extraction of Sm(III). The effects of alkyl chain length of the ionic liquids, solution acidity, contact time, extractant concentration and temperature were tested in terms of the extraction performances. The results revealed that [(CH2)7COOHmor][NTf2] had the optimal extraction capacity, as well as the extraction efficiency of Sm increased with the increase of pH, reaching >99.9% when the pH was 1.8. In addition, the extraction equilibrium could be achieved within 1 min. Moreover, the slope analysis and FTIR spectral studies proposed a cation exchange extraction mechanism for Sm(III) by [(CH2)7COOHmor][NTf2]. The loaded Sm(III) in organic phase was easy to strip with 0.05 mol/L of HNO3, and the [(CH2)7COOHmor][NTf2] remained stable after 5 cycles. The research of transition metal extraction revealed that Sm(III) could be selectively separated from Ni(II) and Co(II) by adjusting the pH value of the solution. Finally, under the optimized extraction conditions, Sm2O3 with 83.9% yield was obtained by the extraction-stripping-precipitation-calcination process, through the large-scale recovery applications of the simulated waste liquid.

Excellent high temperature corrosion resistance of 304 stainless steel immersed in purified NaCl–MgCl2 eutectic salts

Corrosion behaviors of 304 stainless steel (304SS) in NaCl–MgCl2 eutectic salts with purification treatment at high temperature were firstly studied by static immersion under Ar. The weight loss of 304SS were 1.61 mg/cm2 at 500°C and 1.80 mg/cm2 at 600°C, respectively. The annual corrosion rate of 304SS was less than 100 μm, indicating that 304SS possessed excellent corrosion resistance at high temperature. The intergranular corrosion of 304SS at high temperature was accompanied by dissolution of active chromium and iron. Its corrosion of 304SS gradually intensified with temperature increase, especially after 600°C, which provided strong data support for materials selection at high temperature in the future. Owing to the compatibility of 304SS with NaCl–MgCl2 salt, 304SS is suitable for use in the container at high temperature.

High temperature degradation of AISI 304L stainless steel in atmospheres containing CO of biomass to liquid plants at 800 °C

Austenitic stainless steel (ASS) AISI 304L is required for the tube parts in biomass power plants due to high-temperature corrosion resistance properties. However, the high percentage of 35–40 % carbon monoxide and 25–35 % carbon dioxide in biomass atmospheres lead to deterioration in the ASS steels at high temperatures, resulting in chromium carbide formation and intergranular corrosion (IGC). This present work explored the degradation of the stainless steel AISI 304L in a simulated 15 %CO-N2 atmosphere at 800 °C at different testing times between 15 and 60 min. Besides, the ASS samples were pre-oxidized at 800 °C for six hours in air atmospheres before the test. Field emission scanning electron microscope (FE-SEM) and energy dispersive spectroscopy (EDS) were used for carbide characterization. The mass gain of samples was seemingly not changed after prolonging the reduction times. A double loop electrochemical potentiokinetic reactivation (dl-EPR) was used to observe the degree of sensitivity (%DOS) of AISI 304L samples. After the reduction test, the %DOS of samples exceeded the intergranular corrosion severity of 1 %, and the highest %DOS was 7.73 % after the reduction time of 45 min.

High temperature corrosion resistance of FeCr(Ni, Al) alloys as bulk/overlay weld coatings in the presence of KCl at 600 °C

The long-term high temperature corrosion behavior of FeCr(Ni, Al) alloys, both in bulk form and as overlay welds, was investigated in a new experimental setup, in the presence of KCl at 600 °C. All the alloys experienced breakaway oxidation, with the bulk materials exhibiting better corrosion resistance than the overlay weld coatings with similar compositions. All results indicate diffusion-controlled kinetics, and the analysis revealed an improved corrosion behavior connected to an increased Cr content in the inward-growing scale.

Development of Ni-B electroless coating from stabilizer free bath and characterization of high temperature tribological behaviour, scratch and corrosion resistance

The current work investigates the effects of variation of coating bath temperature on friction and wear behaviour of electroless Ni–B (ENB) coatings developed from stabilizer free bath. Coating is applied to specimens made up of AISI 1040 steel. Coatings were deposited at three different coating bath temperatures (85 °C, 90 °C and 95 °C). Field emission scanning electron microscopy, inductively coupled plasma-optical emission spectrometer, and x-ray diffraction were used to characterize the coating for surface morphology, chemical composition, and phase structure respectively. Pin-on-disc tribo-tester was used to estimate the friction and wear behaviour of ENB coatings at room temperature (25 °C), 100 °C, 200 °C and 300 °C. The coefficient of friction was higher at high temperature due to higher roughness of the coatings obtained from stabilizer free bath, adhesion and ploughing. The wear rate at 200 °C or 300 °C was lower compared to 100 °C. Additionally, the ENB coatings were subjected to thermogravimetric analysis which reveals higher thermal stability of coatings obtained at 95 °C. A scratch tester at constant (6 N) and progressive load (5–24 N) was used to estimate the coatings scratch hardness and adhesion. The corrosion behaviour of ENB coatings in 3.5% NaCl was studied using potentiodynamic polarization tests. The Ni-B coated specimens could efficiently provide barrier protection to steel substrate. But the corrosion potential was lower compared to lead stabilized bath.