High Temperature Corrosion Performance Research Articles

Effect of grain size on high-temperature corrosion performance of laser cladding inconel 625 coating

As the calorific value of waste-to-energy incineration continues to rise, the corrosion damage to boilers becomes increasingly severe. The impact of the grain size on the high-temperature corrosion resistance of Inconel 625 coating was investigated. The results indicated that the corrosion performance of the coating in 1:1 NaCl–KCl salts at 700 °C for 120 h was highly dependent on the grain size of the coating. The coating fabricated with a laser power of 1800 W and an overlapping distance of 1.5 mm had an average grain size of 13.7 μm and highest hardness, exhibiting the best corrosion performance, with a corrosion weight loss of 1.4 mg/cm2. Coatings processed under different conditions all formed a three-layered structure, with a NiO outermost layer, a Cr2O3 intermediate layer, and an innermost Cr-depletion zone. Coatings with finer grains formed a continuous and dense protective oxide layer of NiO and Cr2O3 due to the rapid diffusion of alloy elements, effectively preventing the invasion of corrosive media and protecting the substrate from corrosion.

Impact of sulfate to chloride ratio on titanium aluminide coating's high temperature corrosion performance in settings mimicking waste incineration

One major problem with waste incineration is the corrosion of superheater tubes at high temperatures. The presence of sulfate and chloride in this setting poses a severe risk to the boiler's service life. In this work, pack aluminizing was used to create titanium aluminide coating, which was then subjected to five distinct NaCl+Na2SO4 salt combination proportions for 168 h at 600 °C. The outcomes demonstrated that in the presence of solid Na2SO4 deposits, titanium aluminide coating displayed remarkably low corrosion rates. Adding 1/6 NaCl significantly accelerated the rate of corrosion. The electrochemical corrosion resulting from eutectization between NaCl and Na2SO4 was again considerably amplified when the NaCl level was raised to 1/4.

Enhancing high-temperature performance of Inconel 718 LDED samples through hybrid laser polishing post-treatment

ABSTRACT A hybrid laser polishing post-treatment was introduced to enhance the surface quality and high-temperature performance of laser directed energy deposition (LDED) Inconel 718 samples. The surface morphology and microstructure were analysed before and after laser polishing, and the result showed that the surface roughness was reduced by 97.4% and the grains of the recrystallized layer were refined through this post-treatment. Furthermore, the wear resistance, corrosion behaviour, and tensile strength of the laser polishing LDED Inconel 718 samples at the high-temperature of 650°C were investigated detailed. The result showed that the high-temperature tensile strength saw an increase of 14.97%, while both the high-temperature wear resistance and corrosion performance of Inconel 718 exhibited improvements compared to the as-fabricated samples.

High Temperature Corrosion Performance of HVOF and D-gun Formulated Cr3C2-NiCr and Rare Earth Element Doped Cr3C2-NiCr Coating on TP347H Austenite Steel

High Temperature Corrosion Performance of HVOF and D-gun Formulated Cr3C2-NiCr and Rare Earth Element Doped Cr3C2-NiCr Coating on TP347H Austenite Steel

Corrosion behavior of Ni-W coatings with and without macroscopic defects under different corrosion conditions

High pressure and high temperature corrosion performance of Ni-W coatings with and without macroscopic defects were investigated successively in live acid at 100 ℃, spent acid and formation water containing CO2&H2S at 160 ℃ by using weight loss method, surface characterization and high temperature and high pressure electrochemical test. Additionally, the corrosion performance of C110 steels was comparatively studied. The results show that compared with C110 steels, Ni-W coatings have better resistance to each harsh corrosive environment with lower uniform corrosion rate, pit depth and decreased corrosion current density. The corrosion rate of Ni-W coatings in both live acid and spent acid are acceptable for oilfields, and its corrosion rate (0.0978 mm/y) in formation water is categorized as moderate-degree corrosion. The corrosion scale consisting of NiS, Ni3S2 or Ni3S4 and a small amount of Ni(OH)2 is stable, compact and closely combined with the substrate, thus effectively slowing down the corrosion rate of Ni-W coatings during long-term immersion. However, the preferential dissolution of Ni causes a W-rich layer on the top layer of Ni-W coating, probably forming WO2, which tends to crack and aggravates the coating degradation. For Ni-W coatings with artificial defects, the galvanic effect and the catalytic role of Cl- synergistically accelerate the corrosion of the C110 substrate at the defect, and its pit depth is over 100 μm after being corroded in formation water. Notably, the corrosion of the C110 substrate extends laterally and deeply along the coating/substrate interface, promoting the local corrosion disbonding of the coating. Therefore, macroscopic defects in Ni-W coatings should be avoided in their practical application.

Impact of molten salts composition on the corrosion behavior of NiMoCr and CoNiCrAl coatings on L-PBF 316L stainless steel for CSP plants

The high-temperature corrosion performance of NiMoCr and CoNiCrAl coatings produced by high velocity oxy-fuel (HVOF) on laser powder bed fusion (L-PBF) 316L stainless steel substate has been evaluated in presence of three different molten salts used as thermal energy storage (TES) materials for concentrated solar power (CSP) plants. The coatings have an excellent oxidation resistance at 700 °C, showing a percentage of affected thickness lower than 2 %, due to the formation of a protective layer of Cr2O3 and Al2O3 in both NiMoCr and CoNiCrAl coatings, respectively. The carbonates-based molten salt accelerates the corrosion of the NiMoCr coating, affecting around 43 % of the coating thickness, due to the formation of chromates and the high depletion of Mo in the coating. In contrast, the effective protection shown by the CoNiCrAl coating is explained because the grown LiAlO2 after the lithiation process has a high capacity to act as a strong diffusion barrier for metal ions and inhibited the formation of chromates. In the presence of two different ZnCl2 and MgCl2-rich molten salts, the CoNiCrAl coating behaved worse than NiMoCr coating due to the breakage of the (Al,Cr)-rich oxide layer as a consequence of an active oxidation mechanism and due to the formation of voids along the entire thickness, which were identified in 100 % of the coating thickness. The superior corrosion resistance of the NiMoCr coating in presence of the chloride rich molten salts was attributed to the presence of Mo, which fixed the Cr and inhibited the diffusion of oxygen.

High temperature corrosion performance of Inconel 625 hard overlays deposited on stainless steel substrate

AbstractIn elevated conditions, austenitic stainless steels suffer intense damage by corrosion because of the severe oxide scale development. Giving stainless steel a corrosion‐resistant surface coating can prevent excessive damage. In this case, welding‐based overlaying is a potential method to restore the damaged parts as it has a higher productivity rate. This investigation articulates the corrosion resistance behavior of the multiple overlapped Inconel 625 (IN625) weld overlays on the AISI 316L substrate plate. The corrosion resistance at elevated temperatures was investigated with kinetic curves, further revealing the corrosion products from the sample surface. Characterization techniques like scanning electron microscopy with energy‐dispersive spectroscopy, X‐ray diffraction, and Raman spectroscopy were employed to analyze the corrosion products. Hot corrosion kinetics in the molten salt environment (Na2SO4 + V2O5) revealed that the IN625 overlay samples gained a weight of 40.15 mg/cm2, and the substrate had a weight gain of 65.42 mg/cm2. From the hot oxidation kinetics, it is evident that the mass gained by the substrate is more than twice that of the Inconel overlay sample. Furthermore, the formation of oxides and spinel phases rich in nickel (NiO, NiCr2O4) highly influenced the corrosion kinetics of the multiple overlapped IN625 overlay sample. The AISI 316L substrate sample revealed the existence of critical oxide phases such as Fe2O3 and Cr2O3, which were lesser and did not influence the corrosion resistance at 900°C. In the present investigation, the multiple overlapped IN625 weld overlay offered excellent corrosion resistance at high temperature compared to the AISI 316L.

A Dual Encapsulation Strategy for High-Temperature Micro PCM Particles with High Cyclic Durability.

Addressing critical issues such as high-temperature corrosion, leakage, degradation, and subpar cyclic performance is imperative for phase change materials (PCMs), prompting the development of appropriate encapsulation techniques to surmount these challenges. In this study, a dual encapsulation strategy is proposed for high-temperature micro PCM particles. Al-Si core is microencapsulated via the "solvent evaporation-heating curing" method. Subsequently, TiO2 is employed as the skeleton material for form-stable encapsulation of PCM microcapsules by "cold pressed sintering". Detailed analysis of the crystalline phase transformation mechanism in the sintering synthesis pathway of TiO2 underscore its potential as a robust structural material with exceptional thermal stability. Furthermore, the incorporation of hexagonal boron nitride (hBN) results in a substantial enhancement of the thermal conductivity of the composites, increasing by 121.1-131.3%. The prepared form-stable phase change microcapsules (FSPCMs) are subjected to 5000 thermal cycles in the air atmosphere. There is no observed PCM leakage or composite ruptures in the FSPCM. Moreover, the oxidized mass gain is merely 3.3%, signifying exceptional oxidation resistance. Thermophysical analysis indicates that FSPCM can retain 91.3% of the enthalpy after 2000 cycles, with over 80% preservation after 5000 cycles, underscoring its remarkable cyclic thermal durability.

Designing brazing filler metal for heat-resistant nickel alloys of new generation marine gas turbines

The object of research is the processes of the formation of brazed joints and the stressed state. The subject of research is structure, chemical composition, long-term high-temperature strength at a temperature of 900 °C, speed of high-temperature salt corrosion. Existing brazing filler metals have a high-temperature performance of 40–50 % of the performance of the SM93-VI and SM96-VI alloys. Despite this, brazing is the main technique of joining modern heat-resistant cast alloys. Therefore, the development of new brazing filler metals that ensure the formation of joints with increased long-term high-temperature strength is relevant. Ship gas turbine blades operate at a temperature of 900 °C. The purpose of the development of the new SBM-4 brazing filler metal is to achieve long-term high-temperature strength of brazed joints at a temperature of 900 °C at the level of 85–90 % of the strength of heat-resistant alloys SM93-VI and SM96-VI. A two-stage method was used in the development of SBM-4 brazing filler metal. At the first stage, the chemical composition of the brazing filler metal base was determined, taking into account the peculiarities of operating conditions of the blades of marine gas turbine engines and the achievements of materials science of heat-resistant alloys. At the second stage, the depressant and its necessary content were selected. Computer software was used to determine the distribution between the γ- and γ'-phases, taking into account the participation of each element in both dispersion and solid-solution strengthening. Rational limits of concentrations of alloying elements were determined. The criterion was the minimum susceptibility of brazing filler metal to the formation of brittle phases, taking into account the influence of chromium, rhenium, and tantalum concentrations on resistance to high-temperature salt corrosion and high-temperature performance. The long-term strength of SM93-VI and CM96-VI alloys brazed with SBM-4 brazing filler metal is 89–91 % of the strength of the base metal. Technologies of brazing and correction of casting defects have been introduced into production.

Mechanism of Mo content on improving the high-temperature corrosion performance of APS sprayed Ni-clad Al coatings in simulated biomass corrosion condition

The study examined the impact of varying molybdenum content (0 %, 5 %, and 10 % wt) on the high-temperature corrosion resistance of APS-sprayed Ni-clad Al coatings. The coatings were exposed to a simulated biomass-firing environment with pure KCl deposition at 600 °C for 168 h, and a mixed gas containing 15 % water vapor was passed through. The findings revealed that increasing Mo content improved the coating's high-temperature corrosion resistance. The coating with 10 % Mo displayed a continuous layer of Ni and Al oxides on its surface, while KCl was concentrated in the Mo region. Based on the experimental results, a mechanism for how the presence of Mo element contributes to the high-temperature corrosion resistance of NiAl coatings was proposed.

Effect of Mo Addition and Water Vapor on the High-Temperature Corrosion Performance of APS Ni-Al-based Coatings

Effect of Mo Addition and Water Vapor on the High-Temperature Corrosion Performance of APS Ni-Al-based Coatings

Development and High-Temperature Corrosion Performance of MCrAl(Y) Coatings Prepared by Electrochemical Deposition: A Brief Review

Development and High-Temperature Corrosion Performance of MCrAl(Y) Coatings Prepared by Electrochemical Deposition: A Brief Review

Cyclic oxidation and hot corrosion performance of direct metal laser sintered and wrought alloy 718 at 800°C in air and molten salts containing Na2SO4, V2O5 and NaCl

ABSTRACT The main aim of this research work is to investigate the high-temperature cyclic corrosion performance of the wrought and direct metal laser sintered (DMLS) alloy 718 in the air and molten salts NaCl-90%Na2SO4 and three salt mixture (3SM) Na2SO4-10%V2O5-10%NaCl atmosphere for 120 h at 800°C. The microstructure of the wrought and DMLS alloy illustrated the austenitic and dendrite structure. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to evaluate the structure and phase constitutions of the scale. Visual and microstructural evaluation of the alloy post-exposure indicates that corrosion is more prevalent in molten salt conditions, when compared to air, and Cl-species induced the active oxidation in molten salt. The oxide film development and damage mechanism were detailed and explained by a cross-sectional investigation. Significant spalling and sputtering were also noticed in the S3 salt mixture. This might be attributed to the rapid formation of oxide scales by vanadate, followed by dissolution of the oxide in molten sulphate and chloride. The results divulged that both AM-built and wrought alloy exhibited the similar corrosion properties and both the alloys were undergone severe degradation in MS condition. Highlights Alloy 718 was fabricated successfully by the direct metal laser sintering (DMLS) method. Cyclic high-temperature oxidation and corrosion of the alloy were studied at 800°C. The oxidised sample exhibits a lower weight gain with no damage. Due to chlorination and sulfidation, the corroded samples exhibited more oxidation and susceptible.

Effect of laser irradiation on high-temperature crystallization behavior, oxidation resistance, and corrosion performance evaluation of electrodeposited amorphous Ni-P coatings

Amorphous Ni-P alloys crystallize at high temperatures, which leads to the deterioration of resistivity and corrosion resistance. In this study, the use of laser irradiation with the electrodeposition (ECD) process for preparing amorphous Ni-P coatings was investigated; and the resistivity and corrosion resistance were analyzed, which is related to crystallization process, surface morphology, residual internal stress, and oxidation layer. The results indicates that the crystallization rate of Ni-P coating prepared by laser-assisted electrodeposition (LECD) was slower than that of ECD coating. With increasing ambient temperature, the internal tensile stress first decreased and then increased. The LECD coating has better oxidation resistance, with XPS indicating the oxide layer mainly comprised Ni-O compounds. At the same ambient temperature, the resistivity of the LECD coating was higher than that of the ECD coating. The Ni-P coating had better corrosion resistance after heating, and the corrosion mechanism changes from stress corrosion to pitting corrosion.

Microstructure and high temperature performance of 321 SS wall manufactured through wire + arc additive manufacturing

The main aim of the present work is to examine the microstructure and high-temperature corrosion performance of wire + arc additive manufactured (WAAM) 321 stainless steel (321 SS) specimens exposed to molten Na2SO4 + 60%V2O5 salt and air atmosphere at 700 °C under cyclic conditions. The as-built specimens presented a typical layered microstructure with δ-ferrite in the austenite matrix along with small fraction of TiC. The corroded specimen exhibits a high weight gain compared to the oxidized sample, which is attributed to the deposited molten salt. The cracks were developed on the corroded sample attributed to the fluxing of oxides by vanadium and sulphur. Due to good adherent of scale to the steel no spallation were noticed till end of study in both the atmosphere suggesting that WAAM produced steel is suitable for the boiler environment up to 700 °C.

Effect of Laser Irradiation on High-Temperature Crystallization Behavior, Oxidation Resistance, and Corrosion Performance Evaluation of Electrodeposited Amorphous Ni-P Coatings

Effect of Laser Irradiation on High-Temperature Crystallization Behavior, Oxidation Resistance, and Corrosion Performance Evaluation of Electrodeposited Amorphous Ni-P Coatings

High-Temperature Corrosion of APS- and HVOF-Coated Nickel-Based Super Alloy under Air Oxidation and Melted Salt Domains.

Various thermal spraying approaches, such as air/atmospheric plasma spraying (APS) and high-velocity oxy-fuel (HVOF) spraying, are widely employed by plants owing to their flexibility, low costs and the high surface quality of the manufactured product. This study focuses on the corrosion behavior of a Ni superalloy coated with powder Cr3C2-25NiCr through APS and HVOF at 950 °C under air oxidation and Na2SO4 + 0.6V2O5 molten salt environments (MSE). The results show that HVOF-deposited Ni superalloys have higher hardness and bond strength than the respective APS coating. The thermo-gravimetric probe reveals that the Ni superalloys exposed to an oxidizing air environment has a minor mass gain compared to those under the MSE domain for both non-coated and coated samples, in line with the parabola curvature rate oxidizing law. The Ni superalloys show good corrosion resistance but poor oxidation resistance in APS-deposited Ni superalloys under the MSE. HVOF-coated Ni superalloys in both environments exhibit better corrosion resistance and lower mass gain than APS-coated superalloys. The excellent coating characteristics of HVOF-coated Ni superalloys lead to their better high-temperature corrosion performance than APS.

Development of hybrid electrodeposition/slurry diffusion aluminide coatings on Ni-based superalloy with enhanced hot corrosion resistance

Ni/Co-modified aluminide coatings were prepared on Hastelloy-X superalloy by a combined process of electrodeposition and slurry aluminizing. In this regard, pure layers of Ni and Ni-50wt.%Co were initially applied via electrodeposition process and successive aluminization was carried out by a slurry technique. The microstructural and chemical composition characterization of the specimens revealed that a compact and dense aluminide coating was formed with two-layered structure containing the outer Al-rich b phase and inner interdiffusion zone. Moreover, the presence of pre-electrodeposited layers inhibited the outward diffusion flux of elements from the substrate and effectively suppressed the formation of Kirkendall pores. The hot corrosion studies of the obtained coatings indicated that the addition of a pre-electrodeposited layer could enhance the high-temperature corrosion performance of the coatings when exposed to sulfate salt.

Nano-Grain Ni/ZrO2 Functional Gradient Coating Fabricated by Double Pulses Electrodeposition with Enhanced High Temperature Corrosion Performance

Functional gradient materials (FGM) have many excellent properties, and high-performance gradient coating exhibits good prospective application. In this paper, the nano-grain Ni/ZrO2 gradient coating was prepared by double pulse electrodeposition (BP). The surface morphology, crystal structure and electrochemical corrosion resistance of the nano-grain Ni/ZrO2 coating and Ni coating, annealed at different temperatures (400–800 °C), have been compared. In the vertical direction to the substrate surface, the content of ZrO2 increases from 0% to 34.99%. X-ray diffraction (XRD) revealed that the average crystal size of Ni/ZrO2 gradient coating gradually increases from 13.75 to 27.75 nm, and the crystal structure is a face-centered cubic (FCC). The main crystal orientation faces are (111) and (200), while the (200) face exhibited a stronger preferred orientation. Compared with the Ni coating by scanning electron microscopy, the surface morphology of double pulse fabricated Ni/ZrO2 gradient coating was revealed as being smoother, denser, and having fewer pores, and the crystal particle size distribution became narrow. X-ray photoelectron spectroscopy (XPS) shows that the chemical binding states of elements Ni and Zr have been altered. The binding energies of 2p3/2 and 2p1/2 for Ni have been increased, resulting in a higher electron donor state of Ni. The binding energy of 3d5/2 and 3d3/2 of Zr4+ in ZrO2 is decreased, thus becoming better electron acceptors. Chemical bonding has been formed at the Ni/ZrO2 interface. This study demonstrated that double pulse electrodeposition is a promising fabrication method for functional gradient coatings for high temperature applications.

High Temperature Corrosion Performance of Carbon Steel Coated with Iron Aluminide in Mixture of O2 and SO2 Atmosphere

High Temperature Corrosion Performance of Carbon Steel Coated with Iron Aluminide in Mixture of O2 and SO2 Atmosphere