Oxidation Kinetic Curves Research Articles

Oxidation behavior of Ni–Mo–Si alloy coatings fabricated on carbon steel by laser cladding

In this study, Ni–Mo–Si alloy coatings with different compositions were prepared on the surface of AISI 1045 steel by laser cladding. The microstructure and phase composition of different alloy coatings were studied by SEM, EDS and XRD. The oxidation resistance of the alloy coating was investigated in the static air environment at 800 °C. The results showed that: All the γ-Niss/Mo2Ni3Si alloy coatings exhibited similar oxidation behavior and the oxidation kinetics curves followed a comprehensive linear-parabolic law. The total mass gain of N60, N55 and N50 alloy coating were 3.28 mg/cm2, 2.98 mg/cm2, 2.69 mg/cm2, respectively. The oxide layers covered on the alloys were uniform and dense, which were mainly composed of NiO, Fe2SiO4, SiO2 and MoO3. With the increasing Si content in the designed alloy, a continuous SiO2 film formed inside the oxide layer, which could effectively hinder the diffusion of oxygen and Ni2+ in the oxide layer. Among the designed alloy coatings, N50 coating exhibited the lowest oxidation rate and the best oxidation resistance.

High-Temperature Oxidation of Double-Glow Plasma Tantalum Alloying on γ-TiAl

A Ta-modified layer was prepared on γ-TiAl by double-glow plasma surface metallurgy technique. Based on the results of high-temperature oxidation tests at 700, 800, and 900 °C, we studied the morphology, depth profile, and phase of γ-TiAl and Ta-modified layer by scanning electron microscopy, energy spectrum analysis, and X-ray diffraction analysis. Results showed that the Ta-modified layer was tightly bonded to the substrate without voids and cracks, consisting of the α-Ta outer layer and inner diffusion layer. It was found that the isothermal oxidation kinetic curves of the TiAl with the Ta-modified layer followed the parabolic rate law. Ta element promoted the diffusion of Al and formation of uniformly mixed Al2O3/Ta2O5 films, which prevented the inward diffusion of oxygen and help to the improved high-temperature oxidation resistance.

A Study of the Kinetics of Oxidation of Titanium Nanolayers and Their Application in Neutron Optical Devices

The kinetics of oxidation of 10–40-nm-thick titanium films in air is studied by combining X-ray and neutron reflectometry. It is found that the thickness of the oxide layer on the surface of Ti nanolayers does not increase after keeping the samples at room temperature for a year. At temperatures of 100–300°C the oxidation kinetic curves of Ti nanolayers are described by a logarithmic dependence. The obtained results indicate the applicability of the Cabrera–Mott and Evans model approximations to describe the oxidation process of Ti nanolayers in air. Examples of the application of Ti nanolayers in polarizing mirrors and a neutron mirror spin flipper are given.

Structure and Oxidation Resistance of Flamesprayed Fe–Ni–Al Coating

Two types of Fe-Ni-Al coatings as Fe75Ni15Al10 and Fe56Ni14Al30 were successfully deposited on the surface of low carbon steel using the flamespray technique. Coated samples were then annealed in avacuum furnace at 800°C for two hours and evaluated for high temperature oxidation resistance at 800°C for up to 8 cycles. The phases and structure of Fe-Ni-Al coatings before and after the oxidation test were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometer (EDX).According to the oxidation kinetic curve, both of the coating compositions had lower mass gains compared to the low carbon steel. After 8 cycles of exposure, however, the coatings tend to spall off due to the difference in thermal expansion coefficient between the substrate and coating.

Effect of medium temperature precipitation phase and Mn element diffusion mechanism on high temperature oxidation process of repair and remanufacture CoCrFeMnNi high-entropy alloy cladding

In order to study the effect of medium temperature precipitation phase and Mn element diffusion mechanism on the high temperature oxidation resistance of CoCrFeMnNi high-entropy alloy cladding layer, the high-entropy alloy cladding layers were prepared on Q235 substrate by micro-plasma arc process, which were annealed at different temperatures in atmosphere, and then subjected to high temperature oxidation at 900 °C for 100 h. Although the results showed that the microstructure of CoCrFeMnNi high-entropy alloy cladding layer was dendritic structure, the content of Fe, Co and Cr in dendrites was higher, while the content of Ni and Mn among dendrites was higher rather than the generally uniform elements compositions. As the annealing temperature increased, the crystal size in the layer grew slightly. The cladding layer of unannealed and annealed at 900 °C and 1160 °C for 4 h was a single FCC phase structure. However, the annealing cladding layer at 500 °C showed a small amount of Cr-rich BCC phase at the grain boundary, and the 700 °C annealing cladding layer appeared Cr–Fe-rich δ phase at the grain boundary. The alloy cladding layer annealed at different temperatures was subjected to high temperature oxidation experiments at 900 °C for 100 h. The oxidation kinetics curve was parabolic, the diffusion of Mn element controlled the entire oxidation process. The Mn element diffused faster than the other metal cations in the Cr2O3 oxide film and the grain boundary of the matrix, forming an intimate oxide film on the surface and a pore layer depleted in Cr and Mn at an interface portion between the substrate and the oxide film. With the increase of annealing temperature, the grain boundary effect and the interface of Cr and Mn were more favorable for the outward diffusion of Mn element, which formed an intimate oxide film, leading to the gradual severity of oxidation.

High temperature oxidation of Ni-20Cr alloy under compressive stress

The effect of compressive stress on the oxidation kinetics and the revolution of the surface morphology formed on Ni-20Cr alloy was investigated at 900 °C. The study was carried out mainly by comparisons of surface morphology of oxidized samples observed by scanning electronic microscopy. And the oxidation kinetics curves were assessed by two kinds of thermalgravimetric methods. The results indicate that applying the compressive stress induced an increase in the oxidation rate when the applied stress lowered 5MPa. Failure of the oxide scales is depended on the stress level, exceeding 5MPa the oxide scales began to crack and even spall.

Thermal stability and oxidation resistance of FeCrxCoNiB high-entropy alloys coatings by laser cladding

The FeCrxCoNiB (x values in molar ration, x = 0.5–3) high-entropy alloys coatings were prepared by laser cladding on an AISI 1045 steel substrate. Annealing and high temperature oxidation experiments were performed on the FeCrxCoNiB (x = 0.5–3) coatings at 900 °C. The phase structure, morphology, and composition of the coatings and oxidation layers were analyzed by XRD, TEM, SEM, and EDS. Results demonstrated that the FeCrxCoNiB coatings are composed of simple face-centred cubic (FCC) phase and boride. The hardness value of the coatings is significantly improved due to the boride, which is achieved 860 HV at x = 0.5. Cr is conducive to inhibiting the coarsening of boride and enhancing the resistance of coatings to high-temperature softening. The oxidation kinetics curve of FeCrxCoNiB coatings basically follows oxidation dynamic the parabolic law. The selective oxidation in the FeCrxCoNiB coatings changed from the oxidation of Fe to the oxidation of Cr as an increase in Cr content, and finally formed continuous Cr2O3 film. The high temperature oxidation resistance of the FeCrxCoNiB coatings dropped with adding boron into the coatings, which improved contributing to Cr increasing. FeCrxCoNiB coatings gain a better high temperature oxidation resistance as x ≥ 2 (33.3 at.%).

Kinetics and mechanism of high-temperature oxidation of the heterophase ZrSi2-MoSi2-ZrB2 ceramics

The kinetics and mechanism of high-temperature oxidation of dense heterophase ZrSi2-MoSi2-ZrB2 ceramics at a temperature of 1650 °C are studied. The ceramics were fabricated by hot pressing of composite powders prepared by self-propagating high-temperature synthesis with magnesiothermic reduction. The oxidation kinetic curve is described by the power-law function, which indicates that the evolutionary changes in the structure of the formed oxide films significantly affect the course of the oxidation process. The oxidation mechanism involves formation of a multi-layered structure of heterogeneous oxide film, partial dissociation of the ZrSiO4 phase, and formation of secondary MoB and Mo5Si3 compounds. The influence of the ZrSi2, MoSi2 and ZrB2 phases on the structural and morphological features of the formed oxide films and the efficiency of their protective action are shown. Silicon is reduced and zirconium is simultaneously oxidized to ZrO2 in the ZrSi2-ZrSiO4 system at temperatures above 1620 °C in the absence of oxygen or in low-oxygen environment.

Oxidation resistance of nickel-based superalloy Inconel 600 in air at different temperatures

Inconel 600 alloy is widely utilized for high temperature environment application due to the corresponding good oxidation and corrosion resistance properties. In order to estimate the high temperature oxidation resistance of Inconel 600 alloy at various temperatures, the oxidation weight gain of all specimens was measured and fitted for the curve at the temperatures of 700, 800 and 900 °C for exposure time of 100 h. The surface morphology and the component of the oxide film were analyzed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results indicate that the high temperature oxidation resistance of Inconel 600 alloy is excellent blew 800 °C due to the oxidation kinetic curves at different temperatures corresponding to the parabola dynamic rules. This means that the oxidation film protects the substrate well. The dense oxide layer formation containing Cr2O3 and NiCr2O4 at 700 and 800 °C and MnCr2O4 at 900 °C, respectively, is the main reason for the good oxidation resistance. In contrast, the oxide layer peels off easily under applied force as the temperature increases beyond 800 °C, on account of the complicated compositions of the oxide film and the binding force between the oxide layer and the substrate weakening. Corresponding oxidation mechanism is expected to be understood and the oxidation resistance of Inconel 600 alloy is improved through binding force enhancement.

Effect of Y2O3 addition on the microstructure and properties of Ni60 additives by micro-plasma cladding

In this study, the effect of rare earth oxide Y2O3 dispersion particles on the wear resistance and high temperature oxidation performance of Ni60 cladding layer, prepared by micro-plasma cladding, were investigated in detail for the purpose of the additive manufacturing and repair. The results shown that the addition of rare earth oxide Y2O3 reduced the conductivity and thermal conductivity of the nickel-based powder, changing the surface tension of the nickel-based powder after melting and improving the wettability of the molten pool metal, which directly affected the weldability and molding parameters of the cladding layer. When the content of Y2O3 is 1%, the cladding layer was well formed, and the microstructure was mainly composed of cell dendrites and needle-like structures. Moreover, the addition of Y2O3 also changed the thermodynamic conditions of the nucleation growth of the cladding layer, reducing the size of the hard phase such as boron chromium compound, carbon chromium compound, and increasing the distribution concentration. When the Y2O3 content is less than or equal to 1%, the dispersion distribution of Y2O3 refined the microstructure of the cladding layer, decreasing the size of the precipitated phase. The dispersion strengthening enhanced the hardness of the cladding layer and improved wear resistance. The wear mechanism of Ni60 cladding layer was adhesive wear and minute abrasive wear. At 700 °C high temperature oxidation experiment, the oxidation kinetic curve was parabolic, and the cladding layer finally forming a continuous composite oxide film (Cr2O3, YCrO4, NiCrO3, FeCr2O4, SiO2). The presence of rare earth oxide Y2O3 reduced growth rate of oxide film and improved the high temperature oxidation resistance of the cladding layer.

Microstructure and oxidation behavior of the CrMoNbTaV high-entropy alloy

Abstract

Isothermal Oxidation Behavior of Zr-Y Coating on γ-TiAl by Double Glow Plasma Surface Metal Alloying Technique

Oxidation resistance of Zr-Y coating on γ-TiAl alloy prepared by a double-glow plasma surface alloying technique was investigated in static air at 750 °C, 800 °C and 850 °C for 100 h. A pure Zr coating was also prepared for comparison. Addition of Y improved high-temperature oxidation resistance of the alloying coating because of its refining effect and inhibition of cationic diffusion. Oxidation kinetic curves indicated that the high-temperature oxidation resistance of the Zr-Y coating was about eight times higher than that of the bare substrate and about 3 times higher than that of pure Zr coating.

Microstructural evolution and oxidation behaviour of Mo-Si-B coatings on an Nb-16Si-22Ti-7Cr-2Al-2Hf alloy at 1250 °C prepared by spark plasma sintering

Mo-Si-(5, 10, 15)B ternary coatings were firstly coated on an Nb-Si based alloy using the spark plasma sintering technique. The Mo-Si-B coatings consisted of an outer MoSi2/MoB/SiO2/Mo2B5 (Mo5Si3) layer and an inter-diffusion zone, while SiO2 was formed during SPS. The oxidation kinetics curves exhibited parabolic time dependence and 5B coating had the lowest mass gain of approximately 0.41 mg/cm2 after oxidation at 1250 °C for 100 h. The good oxidation resistance results from a dense and protective borosilicate layer formed on coatings and the low growth rate of the inter-diffusion zone beneath the Mo-Si-B coatings.

High Temperature Oxidation Behavior of Fe-Cr Steel in Air at 1000-1200 K

Normal 0 false false false EN-US JA X-NONE MicrosoftInternetExplorer4 The high temperature oxidation behavior of Fe-Cr steel was studied in air at elevated temperatures of 1000, 1100 and 1200 K for up to 72 ks. The mass change of all samples was recorded in order to evaluate their oxidation kinetic. The structure of oxide scales was investigated by mean of X-ray diffraction and SEM-EDX. According to oxidation kinetic curve, the mass gain of oxidized sample increases with increasing oxidation time and temperature. At 1000 and 1100 K, the Fe-Cr steel exhibits an excellent oxidation resistance. As oxidation temperature increase to 1200 K, however, the accelerated oxidation occurred. This is considered due to breakaway oxidation. The Fe-Cr steel forms a duplex oxide layer consisting of Fe-rich oxides in the outer layer and Fe-Cr oxides in the inner layer. The obtained results suggest that the oxidation temperature strongly affects the oxidation resistance of Fe-Cr steel and the structure of formed oxide layer on the steel surface. The influence of oxidation temperature on the oxidation resistance and scale structure is discussed in this paper. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"MS Mincho"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

Oxidation Properties of a Beta-Stabilized TiAl Alloy Modified by Rare Earth Elements

This paper explores the effects of adding rare earth elements (lanthanum or erbium) on the oxidation properties of Ti–43.5Al–4Nb–1Mo–0.1B (TNM) alloy. Isothermal oxidation tests were performed under air atmosphere at 900 and 1000 °C. Mass gain was measured in several steps during the oxidation test, and the oxidized specimens were characterized by XRD and FE-SEM. The results showed that while adding 0.1 at.% rare earth elements (REEs) reduced oxidation rate of the TNM alloy, 0.2 at.% REEs addition increased the mass gain of the alloys. The oxidation curves were fitted by a power-law equation; the results showed that the oxidation kinetic curves of all alloys obeyed parabolic growth kinetics (n = 2). Meanwhile, the activation energy of oxidation was in the range of 40–50 kCal/mol, thereby suggesting that the scale growth was controlled by mass transport in the TiO2 layer. Also, the results of the scale characterization showed that addition of REEs at low level (e.g., 0.1 at.%) could reduce diffusion rate in the scale. However, addition of the higher amounts of La or Er (e.g., 0.2 at.%) due to the lower valency (+ 3) of these elements, as compared with Ti (+ 4), could lead to the increased anion diffusion, the formation of hillocks in the scale and a rise of the oxidation rate.

Microstructure and oxidation behavior of Ti(C,N)-based cermets with in situ synthesized Ni3Al phase

Ni3Al phase was synthesized by in-situ reaction of Ni binder and AlN addition during liquid phase sintering. The microstructure and properties of the Ni3Al-containing Ti(C,N)-based cermets were investigated. The hardness of the cermet increased after addition of 2.5 wt%AlN due to the solid-solution strengthening effect of Ni3Al, and further addition of AlN yielded coarser core-rim grains and decrease of hardness. The transverse rupture strength declined rapidly after addition of 5 wt% AlN, which was attributed to the increase of porosity. After static oxidation at 900 °C, the mass gain of the cermet without AlN addition increased rapidly with oxidation time and followed a quasi-parabolic law. After addition of 2.5 wt%AlN, both mass gain and oxidation rate declined obviously, and the oxidation kinetics curve still presented a quasi-parabolic law. The mass gain increased slightly after addition of 5.0 wt% AlN, and larger addition of AlN up to 7.5 wt% resulted in the changing of oxidation kinetics to a linear law. At 900 °C, the Ti(C,N)-based hard phase and Ni binder phase in the cermet all suffered serious oxidation. The Ti(C,N)-based hard phase was mainly oxidized to TiO2, and Ni binder transformed to complex oxides such as Ni3TiO7 and NiTiO3. As for the cermet with 2.5 wt% AlN addition, the oxidation behavior showed much difference. Though Ni3Al- containing binder was oxidized to Ni3TiO7 and NiAl2O4, both the intermediate oxidation product of Ti(C,N) hard phase, i.e. Ti(O0.19,C0.53,N0.32) and Ni3Al remained stable after dwelling for 4 h. The oxide layer on the cermet with 2.5 wt% AlN addition appeared to be dense and protective, which inhibited the diffusion of oxygen into the cermet and improved the oxidation resistance of the cermets.

High-temperature oxidation behavior and analysis of impedance spectroscopy of 7YSZ thermal barrier coating prepared by plasma spray-physical vapor deposition

Quasi-columnar structure 7YSZ (yttria stabilized zirconia) thermal barrier coatings (TBCs) are prepared by plasma spray-physical vapor deposition (PS-PVD) onto pretreated and un-pretreated bond coating, respectively. An isothermal oxidation experiment of 7YSZ TBCs is carried out in the atmosphere of 950 °C in order to simulate the high-temperature oxidation process of engine blades. The isothermal oxidation process of 7YSZ thermal barrier coatings is investigated systematically by impedance spectroscopy. The electrochemical physical model and equivalent circuit of columnar 7YSZ coatings are established. Results show that the isothermal oxidation kinetic curve of columnar 7YSZ thermal barrier coatings appears to follow the parabolic law. A pretreatment of bond coating can reduce the growth rate of the thermally grown oxide (TGO) layer, restraining the initiation and propagation of microcracks between YSZ and TGO layers. The oxidation rate constants of 7YSZ coatings with pretreated and un-pretreated bond coating are 0.101 × 10−12 cm2·s−1 and 0.115 × 10−13 cm2·s−1, respectively. Impedance analysis shows that the content of oxygen vacancies decreases and the density increases after the TGO layer is oxidized for 150 h. In addition, shrinkage microcracks formed by sintering during the oxidation process is the main reason for an increase of the capacitance and a decrease of the resistance in the grain boundary of YSZ.

High temperature oxidation behavior of a high Al-containing ferritic heat-resistant stainless steel

The high temperature oxidation behavior of a high Al-containing ferritic heat-resistant stainless steel at temperatures of 800, 900, and 1000°C in air were studied in isothermal oxidation tests. The results showed that the isothermal oxidation kinetic curves obtained at different temperatures followed the parabolic law, and the weight gain per unit at 1000°C was significantly higher than that at 800 and 900°C. The oxidation rate at 1000°C was about three times faster than that at 800 and 900°C. Continuous and compact multicomponent oxide films mainly composed of Cr2O3, Al2O3, spinel MnFe2O4, and MnCr2O4 were obtained at 800 and 900°C. The oxide film started delaminating at 1000°C; the outer layer was composed of Cr2O3, spinel MnCr2O4, and MnFe2O4, the middle layer was composed of Fe2O3 and Fe-Cr matrix, and the inner layer was composed of Al2O3 and SiO2. Oxidation resistance at 1000°C was reduced mainly because of porous Fe2O3 and inner oxidation of Al and Si. In addition, the oxidation mechanism was discussed based on kinetic and morphological observations.

Heat protective properties of NiCrAlY/Al2O3 gradient ceramic coating fabricated by plasma spraying and slurry spraying

Al2O3 non-gradient ceramic coating (marked as 1# coating) and NiCrAlY/Al2O3 gradient ceramic coating (marked as 2# coating) were prepared with the plasma spraying and slurry spraying methods, respectively. The coating specimens were characterized by scanning electron microscopy and X-ray diffractometry. The high temperature oxidation kinetics curves of the coatings were examined; the bonding strength between the coatings and the metal substrates was studied, and analyses were conducted on the thermal shock resistance and the failure mechanism of the coatings. The results show that spraying of Al2O3 ceramic slurries can effectively fill the cracks generated during the process of plasma spraying of NiCrAlY coatings, and metallurgical bonds form between the coatings and the metal substrates. α-Al2O3 and rutile TiO2 are the main crystalline phase structures of the temperature resistant ceramic coatings. The oxidation rate constant of 2# coating was 1.323×10−4mg2cm−4h−1, which shows the best resistance to high temperature oxidation. The effect of high-temperature melting of the Al metal in the bonding layer was found to be beneficial to the bonding strength. Under the same temperature conditions, 2# coating had a higher bonding strength than 1# coating, and when the oxidation time was 96h, its bonding strength reached up to 26.9MPa. The thermal expansion coefficient of the NiCrAlY bonding coating fell between those of the metal substrate and ceramic top coating, thus reducing the thermal expansion coefficient difference between the two and decreasing the rate of propagation of the cracks to improve the thermal shock resistance of the coating. An integrated study indicated that 2# coating had a better heat protective performance for the metal substrates.

Effect of Si on high temperature oxidation of 30Cr13 stainless steel

The effect of Si on the high temperature oxidation behavior of the 30Cr13 martensitic stainless steels was investigated. The underlying mechanism was further discussed by oxidation kinetics curves, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. It was observed that the addition of Si can significantly reduce the mass gain per unit area and the oxidation rate of the experimental steels. With the increase of Si content, the film surface composed of the wheat-like oxides turned into the small granular oxides after oxidation for 120 h. The SiO2 film formed on the metal substrate inhibited the outward diffusion of the metal cation and the inward diffusion of the oxygen anion; thus, the high temperature oxidation resistance was enhanced.