High Temperature Oxidation Behavior Research Articles

Effect of Cr content on the high temperature oxidation behavior of FeCoNiMnCr porous high-entropy alloys

Effect of Cr content on the high temperature oxidation behavior of FeCoNiMnCr porous high-entropy alloys

Si modified aluminide coatings on a Ni-base superalloy prepared using Al-Si plasma irradiation: Growth mechanism and oxidation behavior

The growth mechanism and high temperature oxidation behavior of Si-modified aluminide coatings prepared on a Ni-base single crystal superalloy DD98M using vacuum plasma irradiation were investigated. The growth of the coatings under plasma irradiation was much faster than thermal diffusion-controlled process. The coatings comprised an aluminide outer zone, where Si existed as solid-solute, and an inter-diffusion zone where silicide particles precipitated in aluminide matrix. The crystalline structures of the aluminides were found dependent on the irradiation power. β-NiAl was formed at higher irradiation power while δ-Ni2Al3 was formed at lower irradiation power. The β-NiAl coatings had higher oxidation resistance than the δ-Ni2Al3 ones usually, with an exception of one β coating which was prepared at the highest substrate bias which underwent severe internal oxidation. The presence of numerous voids in the oxide scale of Ni2Al3 may be related to the large number of Kirkendall voids present in the as-prepared coating.

Enhanced high temperature mechanical and oxidation behavior of direct energy deposited TiC/Inconel 718 gradient coatings

While Inconel 718 is commonly employed in high-temperature settings, its performance at elevated temperatures is notably diminished in comparison to its performance under ambient conditions. In this study, Inconel 718 (IN718), Inconel 718 with 5 layer of Inconel 718–5 wt% TiC gradient coatings (CG-5), and Inconel 718 with 5 layer of Inconel 718–10 wt% TiC gradient coatings (CG-10) were fabricated using direct energy deposition (DED) to investigate the influence of TiC content on the mechanical and oxidation properties at elevated temperatures through the regulation of microstructural changes. Following the incorporation of TiC, the microstructures underwent a transformation into refined equiaxed crystals, carbides, and columnar crystals, replacing the coarsened columnar crystals and Laves phase present in IN718. Compared to IN718, the high-temperature tensile strength of CG-5 and CG-10 has increased by 80% and 180% at 900 ℃. Meanwhile, the mass gain due to oxidation per unit area of CG-5 and CG-10 has decreased by 23% and 11%, respectively. The results indicate that CG-10 exhibits a combination of highest high-temperature tensile strength and the enhanced resistance to high-temperature oxidation when compared to IN718 and CG-5.

High-temperature oxidation behavior of multi-phase ceramic particles-reinforced TiAl composites with different microstructures

The high-temperature oxidation behaviors of multiphase ceramic particle-reinforced TiAl composites with different microstructures were investigated. The TiAl composites were prepared via spark plasma sintering by introducing 0.5 wt % graphene oxide and 0.3 wt% SiC into Ti-48Al-2Nb-2Cr. The near-γ equiaxed microstructure, dual-phase microstructure, and nearly fully lamellar microstructure were obtained by sintering at 1200, 1250, and 1300 °C, respectively. Moreover, multiphase ceramic particles were uniformly distributed in the TiAl matrix. Cyclic oxidation was conducted at 950 °C in air for 100 h. The TiAl composite with the nearly fully lamellar microstructure exhibited the best oxidation resistance (mass gain of 1.83 mg/cm2) and that with the near-γ microstructure exhibited the worst oxidation resistance (2.47 mg/cm2). The superior oxidation resistance of the TiAl composite with the nearly fully lamellar microstructure is attributed to the uniform distributions of Ti2AlC particles at the α2/γ lamellae interfaces and Ti5Si3 particles at the lamellae colony boundaries, which hinder atomic diffusion. Moreover, the α2/γ lamellae colonies facilitate the formation of Nb-rich and Cr-rich phases at the interface of the oxide layer and substrate, which act as a protective barrier against atomic diffusion.

Influence of temperature, oxygen partial pressure, and microstructure on the high-temperature oxidation behavior of the SiC Layer of TRISO particles

Tristructural isotropic (TRISO)-coated fuel particles are designed for use in high-temperature gas-cooled nuclear reactors, featuring a structural SiC layer that may be exposed to oxygen-rich environments over 1000 °C. Surrogate TRISO particles were tested in 0.2–20 kPa O2 atmospheres to observe the differences in oxidation behavior. Oxide growth mechanisms remained consistent from 1200–1600 °C for each PO2, with activation energies of 228 ± 7 kJ/mol for 20 kPa O2 and 188 ± 8 kJ/mol for 0.2 kPa O2. At 1600 °C, kinetic analysis revealed a change in oxide growth mechanisms between 0.2 and 6 kPa O2. In 0.2 kPa O2, oxidation produced raised oxide nodules on pockets with nanocrystalline SiC. Oxidation mechanisms were determined using Atom probe tomography. Active SiC oxidation occurred in C-rich grain boundaries with low PO2, leading to SiO2 buildup in porous nodules. This phenomenon was not observed at any temperature in 20 kPa O2 environments.

High-temperature oxidation behaviour of additively manufactured and wrought HAYNES 282

AbstractDirect Metal Laser Sintered Haynes 282 specimens as well as wrought ones were subjected to high-temperature exposure at 1000 °C for 100h in air to compare their oxidation behaviour. The specimens were removed from the furnace after 1h, 5h, 25h, 50h and 100h to reveal and study oxidation mechanisms through morphological and cross-sectional examination by using scanning electron microscopy with energy dispersive spectroscopy attachment and X-ray diffraction. Microstructural studies revealed that the oxidation kinetics, determined by changes in thickness scale and depth of aluminium diffusion zone, were mainly driven by the formation of Cr2O3 for the wrought material, and TiO2 for DMLS one. The wrought material was characterized by the oxidation rate equal to 0.96 and followed the logarithmic law. On the other hand, DMLS-manufactured Haynes 282 exhibited oxidation rate of 0.90 and follows the linear law for the thickness scale considerations. However, when the depth of aluminium diffusion was investigated, it had an oxidation rate of 0.87 and followed cubic law.

High-temperature oxidation behavior and mechanical properties of PS-PVD sprayed Yb2Si2O7 environmental barrier coatings

The high-temperature oxidation behavior and mechanical properties of the Yb2Si2O7/Si environmental barrier coatings (EBCs) prepared by plasma spray-physical vapor deposition at 1250 °C and 1350 °C were investigated, and obvious delamination was observed after oxidation for 4000 h. The results showed that element diffusion occurred during oxidation, and the diffusion of oxygen led to the formation of thermal growth oxides (TGO), which induced pores and microcracks. The TGO played a role in hindering element diffusion, but the mismatching coefficients of thermal expansion and phase transition caused vertical and transverse cracks in the TGO layer. These cracks became channels for oxygen diffusion and ultimately resulted in delamination between TGO and the bonding coating (BC) layer. Furthermore, temperature significantly affects the oxidation kinetics of EBCs, and the oxidation within the BC layer alters its elastic modulus. The elastic modulus of the BC layer first increased and then decreased. The oxidation damage was more pronounced at 1350 °C.

Oxidation behavior and oxidation kinetics of film cooling holes at different inclination angles of a Ni-based single-crystal blade

This paper examines the high-temperature oxidation behavior of Ni-based single-crystal turbine blade film cooling holes with varying inclination angles. Utilizing the theory of oxidation kinetics, the concept of an angle influence factor is introduced, and a novel oxidation kinetic equation is formulated. This allows for precise prediction of the oxide/γ′-free layer thickness in film cooling holes across different inclination angles throughout the oxidation process. It offers a new benchmark for future lifespan prediction models, significantly impacting the assessment of the operational life of air-cooled single crystal blades.

The oxidation resistance of Ni nanoparticle incorporated SiOC coating for TiAl alloy

In this work, SiOC coatings incorporated with Ni nanoparticles were fabricated on γ-TiAl alloy by dip-coating. The microstructure and high temperature oxidation behavior of the SiOC-Ni coatings with different Ni contents were investigated. Results showed that the incorporation of Ni nanoparticles improved the oxidation resistance of the SiOC coating at 850 ℃. During thermal exposure to air, the incorporated Ni particles would react with both oxygen and the SiOC coating, forming NiO and Ni2Si, respectively, therefore changing the structure of the SiOC coating. The generation of NiO and Ni2Si is beneficial in reducing the oxygen partial pressure at the coating/substrate interface, thereby facilitating the formation of a protective aluminum oxide layer.

Oxidation behavior of an ultra-high strength and ductile Ni-enriched complex concentrated alloy

Recent research work revealed that Ni43.9Co22.4Fe8.8Al10.7Ti11.7B2.5 HEA is one of the ultra-high strength and ductile superlattice alloys. In this work, high-temperature oxidation behavior of the as-cast Ni43.9Co22.4Fe8.8Al10.7Ti11.7B2.5 alloy was investigated at 1000 ℃ up to 100h. The oxidized samples were characterized using X-ray Diffractometer, Energy Dispersive Spectroscopy, and X-ray Photoelectron Spectroscopy. The results revealed that the initial microstructure of the alloy consists of face centered cubic (FCC) and L12 structures. High-temperature exposure resulted in the formation of Al2O3 and TiO2 scales during the initial hours of oxidation, which eventually spall-off after 25h of exposure allowing further oxidation. The results showed that protective oxide layers such as Al2O3 and TiO2 were not present after 100h of exposure. The external layer of the 100h oxidized sample was composed of Fe, Co, and Ni-rich oxides which are known to have mere effective resistance against oxygen ingression. The alloy which has superior strength and ductility may be used for high temperature applications after attaining the thermally stable fine-grain microstructure by suitable thermomechanical processing / providing oxidation resistance coating / by doping with elements having superior oxidation resistance.

High-temperature oxidation behavior of a novel γ′-strengthened superalloy manufactured by laser-beam powder bed fusion: Effect of post-heat treatment

This study systematically researched the high-temperature oxidation behavior of a γ′-strengthened alloy based on Haynes 230 prepared by laser-beam powder bed fusion (PBF-LB). The results indicate that the experimental alloy showed a higher oxidation resistance than Haynes 230 at 1000 °C. The oxidation products mainly consisted of the outmost MnCr2O4-TiO2 layer, intermediate Cr2O3 layer and inner TiO2 layer. Branched Al2O3 oxides were formed in the interior oxidation zone. Post-heat treatment can increase oxidation resistance by reducing the oxidation rates from 0.0152 mg2cm−4h−1 to 0.0126 mg2cm−4h−1. The decrease in dislocation density and the precipitation of ordered γ' phases can slow down the short-circuit diffusion and lattice diffusion rate of oxygen, and are the main reasons for this improvement. Furthermore, the γ' phase precipitation and dislocation density reduction can provide more sites for Cr2O3 nucleation and reduce the Cr supply required for grain growth. As a result, the Cr2O3 grains on the heat-treated sample surface were smaller.

On the Development of Equiaxed Microstructures in High-Entropy Superalloys and Their Impact on High-Temperature Oxidation Behavior

On the Development of Equiaxed Microstructures in High-Entropy Superalloys and Their Impact on High-Temperature Oxidation Behavior

The mechanical properties and high-temperature oxidation behavior of (TiZr)65-x-yNb15Mo20SixAly refractory high entropy alloys

Herein, the mechanical properties and high-temperature oxidation of (TiZr)65-x-yNb15Mo20SixAly refractory high-entropy alloys were systematically investigated. Results indicate that alloying with Si improves the strength but reduces the plasticity of the alloy. Maintaining a proper ratio of Al/Si is crucial to achieve the optimal performance of the alloy. The (TiZr)50.5Nb15Mo20Si9.5Al5 has excellent high-temperature performance, with a yield strength of 815 MPa at 800°C and a compressive strain greater than 40 %. Moreover, the (TiZr)50.5Nb15Mo20Si9.5Al5 exhibits a superior oxidation resistance compared to (TiZr)55Nb15Mo20Si10 alloy at 1000℃. The introduction of Si enhances the oxidation resistance, decreases the diffusion of the Zr element at 1000 °C and facilitates internal oxidation and the creation of TiNb2O7. However, it is important to note that the doping of Al in the higher Si alloys has negative impacts on the oxidation resistance and mechanical properties.

Effect of micron/nano Nb particles on high-temperature oxidation behavior of TiAl alloy/thermal barrier coating system

In this study, the effect of NiCoCrAlY bond coating modified by micron- and nano-sized Nb particles on the oxidation behavior of a TiAl alloy/thermal barrier coating (TBC) system was investigated. The results show that the addition of micron-sized Nb particles slightly decreased the oxidation resistance of the TNM/TBC system, while the addition of nano-sized Nb particles significantly increased the oxidation resistance. The growth stress from the oxidation of micron-sized Nb particles and the Kirkendall effect lead to localized thickening (tumor effect) of the thermally grown oxide (TGO). Severe internal oxidation occurs in the bond coating modified by micron-sized Nb particles, greatly reducing the mechanical properties and antioxidant properties of the TNM/TBC system. However, these micron-sized Nb particles are deposited at the bond coating/TiAl matrix interface, acting as an in-situ diffusion barrier and partially hindering element interdiffusion. Conversely, nano-sized Nb particles induce the formation of fine columnar crystals in the TGO and promote the external diffusion of Al elements, thereby maintaining a low growth rate and excellent continuity of the TGO. Additionally, the Nb element dissolves into the matrix phase, and the formation of nano Nb-Al₂O₃ core-shell structures effectively improves the deformation resistance and failure resistance of the bond coating.

High-temperature oxidation behavior and subsurface phase transformation of high-Mn high-Al steel

High-Mn steels are widely used in engineering applications because of their high strength, high hardness, and excellent toughness. In the industrial production of high-Mn steel, the steel is easy to be oxidized during the homogenization process, which may affect the properties of high-Mn steel. In this work, high-Mn high-Al steel with composition of (25–32)wt-%Mn-(8–11)wt-%Al-1wt-%C-Fe was prepared, the oxidation behavior and subsurface phase transformation of steel at 800 °C–1200 °C were investigated by thermogravimetric analysis, scanning electron microscope and X-ray diffraction. The results show that the curve of oxidation weight gain with time is in good agreement with linear equations below 900 °C, which obey the parabolic rate law in the temperature range of 1000 °C–1200 °C. The steel matrix would be covered by the oxide scale earlier at higher temperatures, which decreases the oxidation reaction rate and makes the turning point of the oxidation reaction rate reach faster at higher temperatures. The Mn-depleted zone resulting from the selective oxidation of Mn is formed in the steel matrix epidermis, leading to the subsurface phase transformation, which may deteriorate the steel properties.

Protective silicide coating fabricated on ductile VNbTa refractory complex concentrated alloy: Microstructure, high-temperature oxidation and wear behaviors

VNbTa refractory complex concentrated alloy (RCCA) possesses broad application prospects in a wide temperature window owing to its remarkable strength-ductility synergy and super rolling formability, whereas poor oxidation resistance will give rise to excessive wear above 800 ℃. In this contribution, we aim to fabricate a protective silicide coating on VNbTa RCCA for the purposes of enhancing high-temperature oxidation as well as wear resistance. Microstructural characterizations revealed that a uniform and intact coating was obtained under the optimized processing condition of pack cementation. The coating is mainly composed of a single-phase (VNbTa)Si2, along with a thin M5Si3-type interdiffusion zone. Compared with bare alloy, the coated specimens exhibit remarkable oxidation resistance at 1000 ℃ due to the preferential formation of protective SiO2 scale. Meanwhile, the coated specimens maintain desirable wear resistance from 800 ℃ to 1000 ℃. The results of this study would offer a valuable reference to expedite the future engineering applications of RCCAs.

High-temperature oxidation behavior of high entropy carbide (TaNbTiV)C in atmospheres with different oxygen contents

A high entropy carbide (TaNbTiV)C was fabricated via spark plasma sintering of high entropy powders that were prepared using a molten salt method. The as-fabricated high entropy carbide was then investigated for its high-temperature oxidation behavior at 850 °C, under atmospheres with three different oxygen contents (20 vol%, 40 vol%, and 60 vol%). After the high-temperature oxidation process, the main phases observed in all the specimens were incompletely oxidized phase (NbxTi1-x)CyO2-y and oxides (Nb0.5Ta0.5)2O5, TiO2, and Nb2O5. Importantly, the thickness of the oxide layer initially increased and then decreased as the oxygen content increased. When the oxygen content reached 40 vol%, the ceramic displayed severe oxidation behavior with observed thicker of the oxide layer, as well as numerous pores and cracks in the oxide layer. This work provides new insights into the oxidation behavior of high entropy carbides.

Accelerated High-Temperature Oxidation Behavior of Ferritic Stainless Steel under Air/H2+H2O Dual Atmosphere

Improvement in durability is one of the important subjects for utilizing solid oxide electrolyzer cell (SOEC) systems widely. In SOEC stacks, separators are exposed to complexed dual atmosphere (i.e. hydrogen - steam mixed gases and oxygen rich air are on each side). In this study, the degradation phenomena of separator materials (SUS430, ZMG232G10, Crofer22APU) in SOEC dual atmosphere were investigated. The samples were exposed in SOEC dual and simple atmospheres at 700 °C for 500 h. Then, their cross sections were analyzed by X-ray diffraction and scanning electron microscopy/energy-dispersive X-ray analysis. The degradation mechanisms of the separator materials in the SOEC stack operating conditions were discussed. ZMG232G10 and Crofer22APU with high Cr content showed thin oxide layer under both the dual or single atmosphere, while SUS430 with low Cr content showed significant oxidation in the H2-steam atmosphere and on the air side under the dual atmosphere condition. The significant oxidation on the air side of the dual atmosphere of SUS430 observed in this study is a unique phenomenon under the dual atmosphere condition and not observed in a single air atmosphere.

High-temperature oxidation and ablation behavior of (Zr1/3Hf1/3Ti1/3)C ceramic

With the increasing requirements on thermal protection systems of aerospace aircraft, multi-component ultra-high temperature ceramics (MC-UHTCs) are emerging and considered to be candidate materials. In this work, (Zr1/3Hf1/3Ti1/3)C ceramics were prepared by hot pressed sintering, and the behaviors from oxidation to ablation of the ceramics over a wide temperature range was systematically investigated for the first time. The oxidation rate is controlled by oxygen diffusion at initial stage with high activation energy and is slower at lower oxygen partial pressure. The intermediate layer (Zr,Hf,Ti)CxOy, along with the dense oxide layer formed through preferential oxidation, plays a crucial role in hindering oxygen diffusion. Diffusion of Zr, Hf, and Ti elements during oxidation results in Ti enrichment on the ablation surface, enhancing ablation protection. However, high temperatures and prolonged ablation times cause Ti-rich oxides dissipation and significant evaporation of TiO, resulting a porous surface, compromising ablation protection efficacy.

High temperature oxidation behavior of Mo-Zr alloys in pure oxygen condition

In the current study, alloys of Mo-95Zr, Mo-80Zr, Mo-50Zr, Mo-35Zr, Mo-20Zr and Mo-3Zr (at. %) were prepared to investigate the microstructure and oxidation behaviors of the whole composition range of Mo-Zr as-cast alloys. Laves, (Zr) and/or (Mo) intermetallic phases were presented in the primary dendrite, eutectic or peritectic structures in the prepared alloys. The isothermal oxidation process was accompanied by the formation of multi-layer, consisting of the porous and loose ZrO2 and MoO3, which was individually changed from the (Zr), Laves and (Mo). The specimens were examined using a combination of gravimetry and several surface-analytical techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope and electron microprobe. Phases composition on the microstructure and oxidation behavior, and the sources of internal stress and defects formation in oxide layer on these alloys during oxidation have been discussed.