Oxide Scale Research Articles

Process Model for SiC Oxidation for a Large Range of Conditions

A comprehensive process model for 4H‐SiC oxidation is created and calibrated against a very large collection of experimental data. The model reproduces measured oxide thickness for Si‐face, C‐face, and a‐face SiC wafers, in the temperature range 950–1500 °C, in the pressure range 0.25–4.0 atm, in the thickness range 3–1600 nm, and for SiC doping ranging between 1019 cm−3 n‐type and 1019 cm−3 p‐type. The model is based on the Massoud model: Oxidation is driven by oxidants (O2, H2O) which are present in the gas phase, diffuse through the oxide, and form SiO2 at the oxide–SiC interface. For thin oxides, the interface reaction rate includes empirical correction terms which add to the oxidation rate, and which asymptotically approach zero with increasing oxide thickness. For dry oxidation, a remarkable dependence on the O2 partial pressure is discovered: For thick oxides, the oxidation rate scales linearly with the pressure, but the correction term for thin oxides scales with the square root of the pressure. This suggests that the atomistic processes responsible for the fast initial growth of oxides involve the splitting of O2 molecules into two O atoms.

Kinetics and mechanisms of high-temperature oxidation in BCC and FCC high-alloy Fe-based alloys with high volume fraction of carbides

This study conducts a detailed analysis of high-temperature oxidation and microstructural evolution in two high-alloy Fe-based alloys, each characterized by a high-volume fraction of carbides but differentiated by their matrices − body-centered cubic (BCC) and face-centered cubic (FCC), which was achieved by the addition of nickel. By investigating the intricate interplay of factors such as phase composition, nickel content, and the presence of carbides, this research aims to elucidate the diverse oxidation kinetics and underlying mechanisms specific to each alloy type. Results show that the BCC alloy exhibits slower oxidation kinetics compared to its FCC counterpart, suggesting better performance in high-temperature environments. Moreover, while both alloys develop strong adhesive oxide scales primarily composed of Cr2O3, the FCC alloy experiences more pronounced scale spallation and cracking. A faster progression of decarburization was observed in the BCC alloy. This comprehensive comparison highlights how variations in matrix structure, along with nickel content and carbide behavior, critically influence oxidation kinetics, scale adhesion, and the overall integrity of oxide scales. Understanding these nuanced interactions is crucial for designing high-performance alloys tailored for extreme operating conditions.

Tailoring oxidation resistance of Cantor alloy by addition of Ta and Al

High-entropy alloys are widely investigated for applications in the nuclear engineering field, the aerospace sector, and various other high-temperature applications. High-temperature oxidation behaviour is a typical issue in such applications. In the current work, an effort is made to tailor the oxidation behaviour of Cantor alloy (CoCrFeMnNi) in the air at 1000 °C with the addition of Ta and Al. Both CoCrFeMnNiTa as well as CoCrFeMnNiAl alloys exhibit considerable resistance to oxide scale spallation as well as develop multi-layered complex oxide scales. CoCrFeMnNiTa primarily forms rutile-type CrTaO4 oxide, which drastically reduces the inward diffusion of oxygen and nitrogen and suppresses the escape of other alloying elements. Nonetheless, the better result is obtained through the Al addition, as evidenced by the comparatively lower oxidation rate constant of CoCrFeMnNiAl in comparison to CoCrFeMnNiTa alloy. This is attributed to the superior oxidation resistance for CoCrFeMnNiAl could be related to the emergence of distinctive Cr2O3 and Al2O3 scales. Additionally, the oxide scale of CoCrFeMnNiTa was not completely smooth and showed some spallation whereas the oxide scales of CoCrFeMnNiAl remained smooth, continuous, and had stronger oxide-substrate interface adhesion.

CuMn1.7Fe0.3O4 – RE2O3 (RE = Y, Gd) bilayers as protective interconnect coatings for solid oxide cells

Efficient replacement of materials based on critical elements such as cobalt is one of the greatest challenges facing the field of solid oxide cells. New generation materials, free of cobalt show potential to replace conventional materials. However, these materials are characterised by poor ability to block chromium diffusion. This article described the study of CuMn1.7Fe0.3O4 (CMFO) spinel combined with single metal oxide (Y2O3 or Gd2O3) thin films as protective coatings for steel interconnects. CMFO was examined using XRD and TPR. Coated steel samples were oxidised in an air atmosphere at 700 °C for 4000 h. The coatings and oxide scale microstructures and cross-sections were examined by CRI, XRD, and SEM-EDX. The electrical properties of the steel-coating system were evaluated using Area Specific Resistance measurements. Based on the results obtained, it can be concluded that the use of thin layers of rare earth oxides allowed for better blocking of chromium diffusion.

Sliding wear-induced compositional lamination in a VCoNi alloy at elevated temperatures, and its implications for reduced friction and wear

During tribological loading of metallic alloys at elevated temperatures, the thermo-mechanical coupling effect can lead to the development of a distinct tribolayer, profoundly influencing their tribological behavior. This study reports on the compositional lamination in the tribolayer during dry sliding wear of a VCoNi multi-principal element alloy at elevated temperatures. As the temperature increases from 25 °C to 600 °C, the alloy exhibits a remarkable 40% reduction in the coefficient of friction and a notable two-order-of-magnitude decrease in wear rate. The compositional lamination at 600 °C reveals a distinct tribolayer comprising a nanocrystalline-amorphous oxide glaze layer, a Ni-rich dealloyed layer, and a plastic deformation layer. Within the oxide glaze layer, three sublayers are identified, each featuring a nanocrystalline-amorphous nanocomposite structure with unique equiaxed nanograins. Specifically, the outermost sublayer comprises Co3O4, the intermediate sublayer contains a mixture of Co3O4 and Ni2V2O7, and the inner sublayer consists of V2O5. This multilayered structure is attributed to significant differences in the chemical affinity for oxygen among the constituent elements and their respective diffusion rates in the oxide scale. Significantly, the tribolayer formed at 600 °C exhibits a remarkable 70% increase in yield strength compared to its formation at 25 °C, correlating with a substantial reduction in wear. These findings present a novel avenue for designing self-adaptive, high-temperature wear-resistant alloys through the in-situ formation of a protective compositionally-laminated tribolayer.

Unveiling niobium pentoxide and cerium oxide-dispersed ferritic stainless steel for solid oxide fuel cells interconnects

Herein, the effect of niobium pentoxide (Nb2O5) and nano-sized cerium oxide (CeO2) on oxidation behavior and area specific resistance (ASR) of the ferritic stainless steel has been investigated for the development of robust metallic interconnects. An oxide-dispersed ferritic stainless steel alloy is fabricated using the powder metallurgy (PM) process. The morphologies of the alloy before and after oxidation are observed through Scanning Electron Microscope (SEM), Scanning Transmission Electron Microscopy (STEM) and Secondary Ion Mass Spectrometry (SIMS) analyses. Addition of Nb2O5 in the alloy formed a C14 Laves phase of (Fe, Cr)2(Nb, Si). The Laves phase and CeO2 controlled the oxidation behavior of the ferritic stainless steels, consequently reducing the oxide scale thickness and improving the ASR. An alloy with 1 wt% Nb2O5 and 3 wt% CeO2 showed an ASR value of 27.1 mΩ cm2 at 800 °C for 1000 h, which is similar to the ASR value of the commercial Fe–Cr alloy. The results of this study indicate that Nb2O5 and CeO2-dispersed ferritic stainless steel using the PM process can be more advantageous than the conventional process for manufacturing metallic interconnects with complex shapes and reducing production costs.

Comparison of diffusion coatings resistance on ferritic and austenitic-stainless steels at 650 °C in steam oxidation

Iron-aluminide coatings were deposited on T24, P92 and Incoloy 800HT (IN-800HT) by pack-cementation and by a water-based slurry. According to the differences in heat treatments between the two processes, Al-rich phases, i.e. Fe4Al13 and Fe2Al5 were obtained by pack cementation and only B2-(Fe, Ni)Al by slurry. Vertical or horizontal cracks were present on certain coatings, the former being due to the coefficient of thermal expansion (CTE) mismatch with the substrate while the latter were related to the brittleness of the Al-rich phases. The oxidation behaviour of uncoated and coated substrates was studied at 650 °C up to 1000 h under a low steam flow rate (1.07 × 10−5 m/s). The aluminide coatings were very protective on the low Cr substrates (i.e. T24 and P92) because of the formation of a very thin oxide scale compared to the non-protective thick layers of Fe3O4 and Fe2O3 that grew on both uncoated substrates. In contrast, none of the coatings significantly improved the oxidation resistance of the IN-800HT steel despite the growth of a thin oxide layer made of (Fe, Cr)2O3 and (Fe, Cr)3O4 at 650 °C.

Ablation behavior of Y2O3 modified HfC-based coatings for carbon/carbon composites above 2200°C

To improve the ablation resistance of C/C composites, Y2O3 with different contents modified HfC-MoSi2 multi-phase coating was prepared by supersonic atmospheric plasma spraying. The microstructural and phase compositional evolution of as-prepared coating was studied both before and after ablation. The effect of Y2O3 content on the ablation resistance and behavior of the coating was investigated in detail. The results showed that the incorporation of Y2O3 enhances the high-temperature stability of SiO2 oxide films and suppresses their volatilization at elevated temperatures. Furthermore, the formation of Y2Hf2O7 and Y2Si2O7 through the reaction between Y2O3, HfO2 and SiO2 promotes the development of a compact oxide scale, effectively inhibiting gas diffusion into the interior of the coating. Consequently, these improvements contribute to enhanced ablation resistance of the coating.

Accelerated corrosion of FeCrAlTi coating by in situ proton irradiation in molten lead-bismuth eutectic

The synergistic effect of simultaneous proton irradiation and LBE corrosion on FeCrAlTi coating is investigated, and the surface morphology, elementary composition, microstructure and crystal structure of the formed oxide scale are systematically analyzed. The results reveal the accelerated LBE corrosion behavior of proton irradiated FeCrAlTi coating, which can be attributed to irradiation produced defects leading to enhanced diffusion, irradiation induced more porous oxide scale resulting in promoted short-circuit diffusion, and irradiation enhanced adsorption energy of O, Pb and Bi on coating surface contributing to intensive interface interaction.

Towards developing Ti2AlC coatings with improved oxidation resistance via Nb solid solution

Solid solution MAX phase coatings of (Ti1-x, Nbx)2AlC, fabricated using a hybrid technique combining high-power impulse magnetron sputtering (HiPIMS) and DC magnetron sputtering (DCMS), were extensively evaluated for their oxidation resistance at 750 ℃. Compared to Ti2AlC, the oxidation rate of (Ti1-x, Nbx)2AlC significantly decreased, primarily due to the inhibition of non-protective TiO2 oxide growth. A thin, single-layer oxide scale consisting of TiO2 and Al2O3 formed on the (Ti1-x, Nbx)2AlC coatings, while the Ti2AlC coatings were nearly completely consumed after 24 h oxidation. The substitution of Ti4+ with Nb5+ played a crucial role in reducing the number of oxygen vacancies and enhancing the oxidation resistance of Ti2AlC.

Exploration of laser ablation protection for HfC coatings on C/C composites above 2900K

Enhancing the laser ablation resistance of C/C composites is of paramount importance for their prospective application as thermal protection materials, given the rapid advancements in high-energy continuous laser technology. Herein, HfC coating was prepared by chemical vapor deposition (CVD) on the surface of C/C composites to resist the irradiation of high-energy continuous laser. The melting occurred with the formation of oxide products, and these molten phases accumulated at the edge of the ablation pit after laser ablation with two different powers. Furthermore, many cracks were formed around the ablation pit due to the formation of phase transformation stress during ablation. With the increase of laser power, the surface temperature and damage area of the coating increased, and the melting of oxide scale caused by ultra-high temperature was the main reason for the failure of coating. This work could be helpful to provide a theoretical basis for the design and application of laser protective coatings.

Comparative analysis of microstructural, compositional, and grazing incidence characteristics of oxide scale on 316L steel: SLM vs. wrought conditions

The aim of this research is to compare the oxidation behavior and characteristics of oxide scale of 316L steel produced by two methods: selective laser melting (SLM) and conventional casting and forming (wrought). To this end, the initial composition and microstructure of samples produced by those methods were first studied. Thermogravimetric analysis (TGA) and long-term isothermal oxidation tests were carried out on the samples and the oxidation kinetics were compared. The oxidized samples were then examined by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and grazing incidence X-ray diffraction (GIXRD). The results indicated that in the temperature range of 600 °C–900 °C, the oxidation resistance of the SLM alloy is lower than that of the wrought alloy, especially at 800 °C. This is attributed to the combined effect of: i) smaller grain size due to the rapid solidification in the SLM alloy that increases the paths of oxygen penetration, ii) lower presence of chromium and manganese elements in the oxide layer and iii) preferential growth of iron oxide in the form of hillocks on the surface. Surface and cross-section analysis of the oxide layers show that iron oxide is dominant on the surface of the SLM sample at temperatures of 600 °C and 800 °C, and at 800 °C its extended hilly growth leads to significant spallation of the oxide scale and an exponential increase in the oxidation rate. However, at 900 °C, with the formation of a continuous oxide layer containing Fe2MnO4 and CrMnO4, the oxidation rate significantly decreases in both alloys.

Thermodynamic Analysis of Chloride Corrosion in Steel for Energy System Applications in Fe-O-Cl-Na Environments

The assumptions of contemporary energy policies are increasing the share of renewable energy sources. Biomass combustion is developing as an alternative to fossil fuels. However, it faces challenges such as limited corrosion resistance of steel boiler components due to chloride compounds in flue gases and fly ash. This paper provides a comprehensive thermodynamic analysis of chloride-induced corrosion in steel in the Fe-O-Cl-Na environment, focusing on the influence of steam concentration in the gas phase. The study was performed by using the general thermodynamic rules, the thermodynamic properties of the pure components involved in the reaction, and the properties of the solutions formed in the liquid and gas phases. The study also examined the impact of alkali metal chlorides, particularly NaCl, on the formation of NaFeO2 in the passive oxide scale layer Fe3O4/Fe2O3. Furthermore, it investigated the condensation of NaCl vapour formation of low-melting eutectic mixtures in deposits and the resulting consequences on the corrosion process. The role of HCl in the chlorination and oxidation process of steel in melted ash deposits was also discussed. The presented thermodynamic analysis was compared with assumptions of an “active oxidation” model. This study can be a valuable resource for experimental research planning and a guide for preventing corrosion in industrial settings.

Oxidation behavior of harmonic structured high-entropy cantor alloy

Present study deals with the oxidation properties of the harmonic structured high-entropy Cantor (CoCrFeMnNi) alloy at 600 °C, 700 °C, and 800 °C in zero-grade air. The microstructure of the Cantor alloy is modified to a harmonic distribution with grain sizes at shell of ∼2 μm and core of ∼20 μm. The oxidation behavior of the harmonic one is compared with its non-harmonic counterpart and as-received 304L stainless steel. Both the high-entropy Cantor alloys show inferior oxidation resistance than the 304L stainless steel in this temperature range. Studies show that an Mn-rich oxide scale forms on the surface of the Cantor alloys, whereas a Cr-rich oxide scale forms on the 304L stainless steel surface. The high Mn content in the Cantor alloys deteriorates their oxidation resistance. However, the harmonic structure improves the oxidation resistance in the Cantor alloy due to the preferential oxidation of the shell region and the formation of a more compact oxide scale than its non-harmonic counterpart.

Analysis of the Oxidation Behavior and Formation of an Extremely Thin Oxide Layer with a Novel Hot-Stamped Steel

This study investigates enhancing the high-temperature oxidation resistance of hot-stamped steels by adding the Cr/Mn/Si elements to form an extremely thin oxide layer. Under low oxygen partial pressure conditions and high Cr content in the matrix, the oxide layer of a 38Cr3MnNbVMo hot-rolled plate containing the Mo element and high Si content was further thinned to 0.6 μm after cooling at 900 °C for 5 min. The structure of the ultra-thin oxide layer consists of Fe3O4, Mn oxides, FeCr2O4, Cr2O3, and Fe2SiO4 oxides. Compared to other antioxidant elements, under low oxygen partial pressure conditions, Si is more prone to oxidation, forming ultra-thin (22 nm) Fe2SiO4 oxides at the matrix interface. Combined with Cr2O3, FeCr2O4, and Mn oxides, it collectively inhibits the mutual diffusion of external O ions and matrix Fe ions. Furthermore, the addition of the Mo element improves the oxidation resistance. The synergistic effect of multiple powerful oxidation-resistant elements and oxide products effectively inhibits the growth of the iron oxide scale, enhancing the oxidation resistance of hot-rolled, hot-stamped steel.

High temperature oxidation behavior of a Ni–Co-based superalloy

Oxidation behavior of a Ni–Co-based superalloy prepared by vacuum induction melting (VIM) plus electron beam smelting layered solidification technology (EBSL) and VIM plus electro slag remelting (ESR) at 1180 °C was investigated. The predominant oxides from the outer layer to the inner layer are TiO2, Cr2O3, (Al, Ti)-rich oxide and Al2O3, respectively. The (Al, Ti)-rich oxide is considered to be Al2Ti4O9, which is formed by TiO2 and Al2O3. At high temperature, the external oxides experienced significant spalling, particularly in ESR-alloy, which indicated that the EBSL-alloy is more preferable in terms of oxidation resistance. This can be attributed to the presence of finer grains in EBSL-alloy, which facilitates the diffusion of elements and promotes the rapid formation of oxidation scales on the surface of the alloy. Additionally, the presence of a TiO2 layer cover on Cr2O3 reduces the degree of spalling of oxides in EBSL-alloy.

Oxide Scale Microstructure and Scale Growth Kinetics of the Hot-Pressed SiBCN-Ti Ceramics Oxidized at 1500 °C.

In this study, the SiBCN-Ti series ceramics with different Ti contents were fabricated, and the oxidation resistance and microstructural evolution of the ceramics at 1500 °C for different times were explored. The results show that with the increase in oxidation time, pores and bubbles are gradually formed in the oxide layer. When the oxidation time is less than or more than 4 h, the Ti(C, N) in the ceramics will maintain its initial structure or mostly transform to TiN. The introduction of Ti content can promote the formation of rutile silicate glass, thus healing the cracks and improving the oxidation resistance of the ceramics effectively.

General corrosion behavior and mechanism of ferritic/martensitic steel with and without TaWVCr coating in static oxygen-saturated lead bismuth eutectic at 550 °C

Here in present work, the ferritic/martensitic (F/M) steel HT9 and refractory TaWVCr high entropy alloy coated HT9 were tested in a static oxygen-saturated lead bismuth eutectic (LBE) at 550 °C through corrosion tests and slow strain rate tension tests to investigate the corrosion behavior and mechanism. The fracture pattern of HT9 and TaWVCr/HT9 both show the ductile fracture. Comprehensive microstructural characterizations from atomic-scale examinations to micro-scale fracture analyses were performed to illustrate the underlying mechanisms of the liquid LBE corrosion. It was revealed that the corrosion of HT9 is related to the surface oxide scale cracking, which propagates into the matrix but terminated in the Cr2O3 enriched zone at the crack tip. On the contrary, the stress concentration caused by local degradation of the TaWVCr coating accelerates the oxidation and dissolution of the coating in LBE, leading to the formation of a duplex oxide layer underneath the coating, which allows cracks initiate in the magnetite layer and annihilate in the chromite layer. The micrometer-scale penetrative oxide layer was found within the matrix, due to the inward diffusion of O through the diffusion channels such as dislocation channels of the matrix and the dissolution channels of the coating and this can accelerate the oxidation corrosion of the matrix.

Effect of Heat Treatment Temperature on Isothermal Oxidation of Ni-based Fe-33Ni-19Cr Alloy

This project studies the influence of different grain sizes of Ni-based Fe-33Ni-19Cr alloy obtained from heat treatment procedure on high temperature isothermal oxidation. Heat treatment procedure was carried out at two different temperatures, namely 1000℃ and 1200℃ for 3 hours of soaking time, followed by quenching in the water. These samples are denoted as T1000 and T1200. The heat-treated Ni-based Fe-33Ni-19Cr alloy was subjected to an isothermal oxidation test at 950℃ for 150 hours exposure. Oxidized heat-treated alloys were tested in terms of oxidation kinetics, phase analysis and surface morphology of oxidized samples. Oxidation kinetics were determine based on weight change per surface area as a function of exposure time. Phase analysis was determined using the x-ray diffraction (XRD) technique and surface morphology of oxidized samples was characterized using a scanning electron microscope (SEM). As a result, the heat treatment procedure shows varying grain sizes. The higher the heat treatment temperature, shows an increase in grain size with a decrease in hardness value. The oxidation kinetics for both heat-treated samples showed an increment pattern of weight change and followed a parabolic rate law. The oxidized T1000 sample recorded the lowest parabolic rate constant of 3.12×10–8 mg2cm–4s–1, indicating a low oxidation rate, thus having good oxidation resistance. Phase analysis from the XRD technique recorded several oxide phases consisting of Cr2O3, MnCr2O4, and (Ti0.97Cr0.03)O2 oxide phases. In addition, a uniform oxide layer is formed on the oxidized T1000 sample, indicating good oxide scale adhesion, thereby improving the protective oxide behavior.

Oxidation behaviors of a Ni–Cr–W based superalloy with different microstructures

Oxidation behaviors of a Ni–Cr–W based superalloy were investigated in terms of microstructural characteristics. It was found that the specimens with small grains present a better oxidation resistance owing to their higher density of grain boundaries. Based on analyses of the products of oxidation, the oxidation kinetics, the morphologies and the structures of oxide scales, the oxidation mechanisms correlated with the outward diffusions of metal cations were proposed. The results of this work indicated that grain refinement is one of effective measures to enhance the oxidation resistance of the investigated alloy.