Hot Corrosion Research Articles

Effect of impact angle on hot corrosion resistance of abrasive water jet peened Ti-6Al-4V alloy

Effect of impact angle on hot corrosion resistance of abrasive water jet peened Ti-6Al-4V alloy

Influence of NiCrAlY coating on anti-corrosion of M951 alloy

M951 alloy is a cast nickel-based super-alloy widely used in gas turbines and aircraft engines, thus a suitable high temperature protective coating must be applied on its surface to enhance the corrosion resistance. In this research, NiCrAlY coating was deposited on M951 by arc ion plating. TGA at 1100 °C, cyclic oxidation at 1000 °C and hot corrosion in molten Na2SO4+25 wt% K2SO4 salt at 850 °C of M951 bare alloy and NiCrAlY coating specimens were investigated respectively. After TGA and cyclic oxidation, mixed oxides of NiO, NiAl2O4, Nb2O5 and Al2O3 formed on M951 surface, which spalled seriously during cyclic oxidation process. Thin, continuous and adhesive α- Al2O3 formed on the surface of NiCrAlY coating after both oxidation process. In molten Na2SO4+25 wt%K2SO4 salt at 850 °C, catastrophic corrosion occurred for the M951 alloy only after 10 hours, while thin and continuous θ- Al2O3 film formed on the surface of the NiCrAlY coating. In a word, NiCrAlY coating greatly improved the high temperature oxidation and hot corrosion resistance of the M951 superalloy. This study will further refine the oxidation and corrosion behaviors of M951 superalloy under different high temperature protective coatings and provides theoretical and experimental basis for the application of M951 superalloy in corrosive environments.

Corrosion resistance analysis of Al2O3-TiO2 composite ceramic coatings on carbon steel pipe surfaces

This study investigates the corrosion resistance of Al2O3-TiO2 composite coatings reinforced with multi-walled carbon nanotubes (MWCNTs) on carbon steel pipe surfaces. Coatings were deposited using atmospheric plasma spraying (APS) and high velocity oxy-fuel (HVOF) techniques. Microstructural analysis revealed that HVOF-sprayed coatings exhibited denser and more homogeneous structures compared to APS-sprayed coatings. Electrochemical tests in 3.5 wt% NaCl solution showed that the HVOF-sprayed Al2O3-13 wt% TiO2-1.5 wt% MWCNT coating demonstrated the lowest corrosion current density of 7.6 × 10−9 A/cm2 and the most positive corrosion potential. Hot corrosion tests in a simulated boiler environment (500°C, 1000 h) revealed that this coating also exhibited minimal weight gain (0.9 mg/cm2) and thickness loss (2 μm). The corrosion rate of the optimal coating was 0.05 mm/year, significantly lower than the bare carbon steel (2.45 mm/year). XRD analysis of corroded samples showed that HVOF-sprayed coatings maintained their original phase composition without detectable substrate corrosion products. The superior corrosion resistance of the HVOF-sprayed Al2O3-13 wt% TiO2-1.5 wt% MWCNT coating is attributed to its optimized composition, dense microstructure, and the reinforcing effect of MWCNTs. These findings provide valuable insights for developing advanced coating solutions to mitigate corrosion-related challenges in the oil and gas industry and other harsh industrial environments.

Investigation of damage on FeCr26Ni36Co15W5 alloy reduction furnace tube during service

ABSTRACT The microstructure and mechanical properties of tungsten powder reduction furnace tube are investigated in this work. After service, the lamellar and skeleton-shape primary carbides of FeCr26Ni36Co15W5 alloy coarsened and formed a continuous network, much fine secondary carbide precipitated in the dendrite interior. The tensile strength and ductility of FeCr26Ni36Co15W5 alloy decreased. And, the creep strength of FeCr26Ni36Co15W5 alloy has reached the end of the service life. Meanwhile, the corrosion products were studied by XRD and XRF. It was found that the corrosion products were Na2WO4·2 h2O, Na2CO3·H2O and Cr4Ni15W，and the evaporation of catalyst (Na2CO3) results in a large amount of Na2CO3·H2O in the corrosion products. The hot corrosion mechanism of the reduction furnace tube is Type I hot corrosion.

High Temperature Corrosion Study on NiCr Coated Low Alloy and Mild Steel

Cyclic hot corrosion behaviour of bare and D-gun sprayed NiCr coated low alloy and mild steel sample having dissimilar coating thicknesses viz. 0.2-0.25 mm and 0.25-0.30 mm have been studied in molten salt environment mixture of Na2SO4 - 25wt. % NaCl at temperature of 750 ̊C. Corrosion kinetics were analysed and parabolic rate constants (Kp) for both bare and coated sample were calculated and observed that 0.2-0.25 mm thick NiCr coated specimen showed better resistance against high temperature corrosion for both materials. SEM/EDX analysis was carried out to examine scale formed on the bare and coated sample after hot corrosion.

The Effect of Spray Distance on the Hot Corrosion Behavior of HVOF‐Sprayed NiCrAlY Coatings in a Simulated Gas Turbine Environment

ABSTRACTTo utilize the unique properties of coatings produced using the high‐velocity oxy‐fuel (HVOF) method, this study examined the effect of spray distance on the hot corrosion behavior of NiCrAlY coatings deposited on a steel substrate. The coating samples were obtained at spray distances of 20, 25, and 30 cm. The flow rates of oxygen and propane were maintained constant at 300 and 60 lit/min, respectively. Additionally, the powder feeding rate was 32 g/min. The samples were then subjected to the hot corrosion test in a salt mixture of Na2SO4−60% V2O5 at 900°C in an ambient atmosphere. The surface and the cross section of the samples were observed using a scanning electron microscope (SEM) and the chemical composition of different sections was determined by energy‐dispersive spectroscopy (EDS). The phases were also characterized using X‐ray diffraction analysis (XRD). The best corrosion resistance was found in the sample coating formed at a spraying distance of 20 cm, as the results showed that increasing the spraying distance led to a reduction in the thermal and kinetic energy of the flame, resulting in increased porosity in the coating. This behavior can be attributed to the low oxide content of the coating, the higher aluminum content, and the richer NiAl phase, which serves as a reservoir for aluminum.

Investigating Hot corrosion, CMAS, and Thermal Shock Behaviour of Double-layer YSZ/La2Ce2O7 + YSZ Thermal Barrier Coatings

AbstractIn this work, new double-layer YSZ/La2Ce2O7 (LC) + YSZ coatings were developed using air plasma spraying (APS). The surface of the prepared coatings was relatively smooth and consisted of melted and partially melted areas. Their resistance to hot corrosion, CaO-MgO-Al2O3-SiO2 (CMAS), and thermal shock were examined. YSZ was added to the upper layer to enhance the lanthanum cerate (La2Ce2O7, LC) properties. During the hot corrosion tests, the corrosion salt reacted with the upper layer, and the CeO2 phase and new corrosion products were identified. The main phase was LaVO4, and the secondary phases were CeVO4 and YVO4. SEM confirmed the formation of new, cuboidal-shaped corrosion products. The infiltration of CMAS led to the formation of additional new products: Ca4MgxAl4Si(6-x-γ)O14 and Ca2.8(LaxCe1-x).6(SiO4)O6-4x. SEM revealed CMAS infiltration through the upper layer in the form of islands. Following the thermal shock resistance tests, the upper layer gradually peeled off, and the coating survived 67 cycles. Possible failure mechanisms were identified, and failure was attributed to the spallation of the upper layer from the surface layer by layer. After all tests, the top layer showed partial spalling and delamination. This was mainly caused by the reaction of corrosive salt or CMAS with the top layer, which changed its composition, leading to the formation and propagation of cracks and, ultimately, the separation of part of the upper layer. Peeling of the upper layer through mainly horizontal cracks was observed after hot corrosion, CMAS and thermal shocks. The NiCrAlY bond coat and YSZ interlayer remained undamaged.

Improving hot corrosion behaviour of Cr3C2-25NiCr coatings by reinforcing nano yttria stabilized zirconia at 850 °C

Yttria-Stabilized Zirconia (YSZ)-enhanced Cr3C2-25NiCr coatings were applied to T22 boiler tube steel using the High Velocity Oxy Fuel (HVOF) method. Conventional Ni-20Cr, 5 wt.% YSZ- Cr3C2-25NiCr, and 10 wt.% YSZ- Cr3C2-25NiCr composite coatings were prepared. High-temperature corrosion tests were conducted on both uncoated and coated samples in a Na2SO4-60%V2O5 environment at 850°C under fluctuating thermal conditions. These experiments were carried out in a silicon tube furnace at high temperatures, with each sample subjected to 50 cycles of exposure. Each cycle consisted of 1 hour in the corrosive environment followed by 20 minutes of cooling at room temperature. Corrosion products were analyzed using energy-dispersive x-ray analysis (EDS) and scanning electron microscopy (SEM). The addition of YSZ to the Cr3C2-25NiCr coatings significantly improved corrosion resistance, with the Ni-20Cr, 5 wt.% YSZ-Ni-20Cr, and 10 wt.% Cr3C2-25NiCr coatings reducing overall weight gain by 73.08%, 84.70%, and 89.96%, respectively, compared to uncoated T22 steel.

Enhancing anti corrosion properties of plasma-sprayed ZrO2-25 wt%CeO2-2.5 wt%Y2O3 thermal barrier coatings via nanostructure engineering

The current research aimed to enhance the corrosion resistance of (i) the CaO-MgO-Al2O3-SiO2 (CMAS) and (ii) the hot corrosion of the Na2SO4-55 wt%V2O5 environments. Conventional thermal barrier coatings (TBCs) with a composition of ZrO2-25 wt%CeO2-2.5 wt%Y2O3 (micro-CYSZ) were replaced by nanostructured coatings (nano-CYSZ) with a similar composition. This replacement was achieved by applying the desired coatings using the atmospheric plasma spraying (APS) process on IN738LC/CoNiCrAlY. Corrosion and hot corrosion tests were conducted in the CMAS and Na2SO4-55 wt%V2O5 environments at 1100 °C and 950 °C with 4-h cycles. In terms of resistance to CMAS corrosion and hot corrosion in the Na2SO4-55 wt%V2O5 environment, the nano-CYSZ coating exhibited better performance compared to the micro-CYSZ with a similar composition. The use of nanostructuring, including the formation of dual structures consisting of unmelted nano-sized particles and melted particles in the top layer of the TBC, resulted in delaying the penetration of molten salts and consequently improving the resistance to the CMAS and Na2SO4-55 wt%V2O5 environments.

Enhancing hot corrosion resistance of N-doping NiCoCr-based superalloy coatings fabricated by directed energy deposition in mixed molten salts

Here, a NiCoCr-based superalloy coating has been developed in ultra-supercritical environments. However, optimizing the coating composition to enhance the anti-corrosion performance remains a formidable challenge. This research introduced an innovative N-doping strategy to enhance the hot corrosion resistance of the coating by utilizing directed energy deposition. The hot corrosion behavior at 700 °C of the coating with N-doping reinforcement was investigated. Detailed characterizations of the microstructural evolution and corrosion products were conducted. The results showed that the improvement of hot corrosion resistance was attributed to the continuous protective film retained in the N-doping reinforced coating, which inhibited the inward diffusion of corrosive media to retard the chlorination and sulfuration reaction. This work provides new insight into the design of corrosion-resistant superalloys and highlights the potential of N-doping superalloy coating in extreme environments.

Evaluation of the corrosion and oxidation resistance of NiCoCrAlY cladding on CMSX-4 by laser cladding

This study uses laser cladding to investigate the hot corrosion and oxidation behavior of CMSX-4 claddes with NiCoCrAlY powder. High-temperature oxidation tests were conducted at 1050°c for 50, 100, 150, and 200 h on 4 samples, while 6 samples underwent hot corrosion testing at 850°c for 6 h. The innovative application of laser cladding enables the creation of a γ′ and β interdendritic phase microstructure. High-temperature oxidation tests reveal a growth rate of 0.05 μm/h in oxide layer thickness between 50 and 200 h, accompanied by a surface weight increase rate of approximately 0.8 mg/cm2.h. The oxide layer's regeneration, continuity, and density are observed at 200 h, highlighting the innovative potential of this technique. Fracture oxidation is observed at 150 h in some TGO layer regions, but at 200 h of oxidation, the TGO layer's regeneration, continuity, and dense TGO was observed at the cladding interface. The TGO forms at 1050°c consist of Al2O3, Cr2O3, and CoO oxides, with Al2O3 as the main oxide phase. The study's findings demonstrate the ability of laser cladding to enhance the thermal protection of CMSX-4, showcasing a promising innovation in the field.

Synergistic Improvement in Ductility and Hot Nitric Acid Corrosion Resistance of LPBF Ti-6Al-4V Alloy via Hot Isostatic Pressing

Synergistic Improvement in Ductility and Hot Nitric Acid Corrosion Resistance of LPBF Ti-6Al-4V Alloy via Hot Isostatic Pressing

Enhanced hot corrosion resistance of AlCoCrFeNi2.1 high entropy alloy coatings by extreme high-speed laser cladding

Extreme high-speed laser cladding (EHLC) and multiple laser remelting (EHLC-MR) are used to improve hot corrosion resistance of AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) coatings by refining their microstructures, introducing low angle grain boundaries (LAGBs) and high densities of dislocations as well as higher compressive residual stresses (CRSs) in the coatings. The experimental results show that finer microstructure, more LAGBs and high densities of dislocations are beneficial to increase Al2O3 nucleation sites and promote the uniform formation of the oxide layer on the coating surface. On the other hand, higher CRSs suppress the initiation and propagation of cracks as well as enhance the adhesion between the oxide layer and the substrate. Thus the hot corrosion resistance of the EHEA coatings under a molten salt of 75% Na2SO4 + 25% NaCl at 900°C is improved significantly. These novel results provide effective approach for designing elevated-temperature materials.

Solid/Molten Na2SO4-Induced Hot Corrosion Behaviors of Mar-M247 Alloy with CVD Aluminide Coatings

Solid/Molten Na2SO4-Induced Hot Corrosion Behaviors of Mar-M247 Alloy with CVD Aluminide Coatings

Hot Corrosion Behaviour by Na2SO4 Deposits of the 1st Generation AM1 Single-Crystal Nickel-Based Superalloy at 750 °C

Hot Corrosion Behaviour by Na2SO4 Deposits of the 1st Generation AM1 Single-Crystal Nickel-Based Superalloy at 750 °C

Effect of CrN coating on the hot salt corrosion fatigue behavior of titanium alloy

The dwell fatigue behavior of CrN coated titanium alloys were carried out in air and hot salt corrosive environment at 500 ℃. The results indicate that the decrease of the elastic modulus difference between the coating and the substrate alleviates the deformation mismatch issue at high temperature. Stress relaxation at the crack tip caused by Cr transition layer oxidation can improve the fatigue properties of the coated samples. Furthermore, the CrN coating enhances the corrosion fatigue properties, which is related to the barrier effect of the coating on the corrosive medium. The crack growth mode in the substrate transition from stress corrosion crack to fatigue damage crack.

Hot Corrosion Performance Analysis of Microwave Heat-Treated Al2O3-Based Coatings Deposited on SA 210 Grade-I Boiler Steels

Hot Corrosion Performance Analysis of Microwave Heat-Treated Al2O3-Based Coatings Deposited on SA 210 Grade-I Boiler Steels

Hot corrosion of sputtered nanocrystalline coating with and without preoxidation and arc ion plating coating on a Ni-based single-crystal superalloy

Hot corrosion of the N5 nanocrystalline coating with 0.5 wt% Y addition with and without preoxidation under 75 wt% Na2SO4 + 25 wt% NaCl molten salts at 900 °C was investigated, in comparison with that of the NiCrAlY coating under the same condition. The results showed that the nanocrystalline coating with nano-columnar structure suffered more severe corrosion than NiCrAlY coating. The high density of grain boundaries in the nanocrystalline coating facilitated inward penetration of the corrosive medium and accelerated the destruction of the scale. Preoxidation significantly enhanced the corrosion resistance of the nanocrystalline coating by forming an exclusive Al2O3 scale on the surface that could prevent molten salt from accessing the coating surface. The coating preoxidized at 1000 °C exhibited the highest corrosion resistance with the least internal corrosion. Y stabilized Ta and/or S during preoxidation and subsequent corrosion process, improving the purity and stability of the scale. The coating preoxidized at 1100 °C performed worse than that at 1000 °C. The inferior corrosion resistance was attributed to the more Ta oxides segregation and faster consumption of Al at the higher preoxidation temperature, accelerating scale destruction during hot corrosion.

Cyclic hot corrosion behavior and mechanism of GH4738 superalloy in mixed molten salt

The research on the hot corrosion resistance of nickel-based superalloys is critical to determining and enhancing their service life. Therefore, this study investigates the cyclic hot corrosion behavior of GH4738 alloy coated with a mixed salt (75 wt% Na2SO4+25 wt% NaCl) at 750 °C and 800 °C. X-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and transmission electron microscope (TEM) are used to analyze the phase compositions and film structures of the corrosion products, as well as to explore the corrosion mechanism. The results show that a thicker oxide layer is formed at higher temperatures, indicating poorer hot corrosion resistance at elevated temperatures. The corrosion products form at both temperatures to show a distinct layered structure, the outer layer is mainly composed of Cr2O3 and a small amount of TiO2, while the inner layer consists of Al2O3, CrS, and TiS. In addition, it is found that the corrosion mechanism of O, S, and Cl elements in the corrosion process is synergistic and accompanied by alkaline melting.

Accelerated design and fabrication of thermal protection coating via high-throughput experiments and machine learning

For the engineering applications of thermal protection materials (TPMs), the demand targets are often multiple such as high-temperature oxidation, hot corrosion, high temperature/speed ablation, etc., which is a challenging problem for developing a tailored property by an efficient and economical method. In this work, using modified silicide-based coating as the model materials, a hybrid model for the design of TPMS with tailored properties is developed through the high-throughput experiments combined with the machine learning (ML) method. Among the four data sets, XGboost model has the smallest bias in the predicted values, the largest coefficient of determination (R2) value, and the smallest mean square error (MSE). Our work exemplifies the potential of high-throughput experiments and ML-assisted design in advancing the discovery and development of novel TPMS.