High-temperature Oxidation Resistance Properties Research Articles

Laser surface cladding of CoNiCrAlY as Bond Coat on INCONEL718 substrate for thermal barrier coating application

This study delves into laser surface cladding of CoNiCrAlY onto Inconel718 employing a 6.6 kW continuous wave diode laser with varying process parameters. The resulting microstructure, microhardness, and isothermal oxidation resistance are meticulously assessed. Laser surface cladding yields a defect free microstructure with the presence of gamma (γ), gamma prime (γ’) and beta (β) phases. There is negligible dilution at the interface with a minimum HAZ. The average microhardness of the clad zone ranges from 425 to 465 HV, increasing with increase in scan speed and decrease in power. The high temperature oxidation resistance property of the clad surface is superior to the same developed by high velocity oxy fuel spraying.

Unveiling the oxidation mechanism of CrTaTiMo refractory medium-entropy alloys: A synergy of density functional theory and ab initio molecular dynamics

The demand for advanced materials capable of withstanding extreme high-temperature conditions has led to the development of novel High-Entropy Alloys (HEAs). Recent works indicate that forming a CrTaO4 protection layer gives HEAs excellent long-term oxidation resistance. In this study, the high-temperature oxidation resistance properties of CrTaTiMo Refractory Medium-Entropy Alloys (RMEAs) were assessed by Density Functional Theory (DFT) and ab initio Molecular Dynamics (AIMD). Through the oxygen adsorption and diffusion calculations, we demonstrated the preferential oxygen adsorption sequence on the surface of the RMEA as Ti, Ta, Cr, and Mo. Furthermore, our analysis identified the sites featuring Ta as subsurface atoms were the weakest locations for oxygen atom diffusion. The dynamic oxidation mechanism of oxygen molecules on CrTaTiMo RMEA was investigated by AIMD simulations. The results confirmed that the adsorption and dissociation of O2 molecules on the alloy surface. Additionally, the diffusion of the O atom took place at temperatures greater than 873 K and confirmed the O-attracting feature of Ta atoms. Moreover, electronic structure calculations confirmed the bonding of oxygen atoms with those four metal elements. This study could serve as a valuable reference for the strategic development of the CrTaTiMo-based RMEAs or RHEAs for high-temperature, long-term oxidation resistance applications.

Effect of compound alloying on high temperature oxidation resistance property of Ti2AlNb alloy

Effect of compound alloying on high temperature oxidation resistance property of Ti2AlNb alloy

Tribological Behaviors and High-Temperature Oxidation Resistance Properties of Wtavcr Alloy Coating

Tribological Behaviors and High-Temperature Oxidation Resistance Properties of Wtavcr Alloy Coating

The high-temperature oxidation resistance properties of magnesium alloys alloyed with Gd and Ca

This work studied the high-temperature oxidation resistance properties of Mg alloys with Gd and Ca. The oxidation property of Mg-3.5Gd-xCa (x = 0, 0.5, 1.0 and 3.0 wt%) alloys followed parabolic oxidation kinetics at 500 °C. A stable oxide film was formed on the alloy surface and limited further oxidation. The oxide film was composed of Gd2O3, MgO and MgCO3 for Mg-3.5Gd and was mainly CaO and CaCO3 with increasing Ca content for Mg-3.5Gd-xCa alloys. The high oxidation affinity of Ca caused it to be oxidized preferentially and the fast diffusion of Ca in Mg alloys provided a source for the continuous oxidation of Ca at the surface. The parabolic rate constant, grains size and surface roughness of the oxide film increased with the increasing Ca content in Mg-3.5Gd-xCa alloy. The understanding of multi-element alloying on the oxidation behavior of Mg alloy is helpful for the design of multi-element oxidation-resistant Mg alloys.

Effects of Bias Voltages on the Structural, Mechanical and Oxidation Resistance Properties of Cr–Si–N Nanocomposite Coatings

Cr–Si–N nanocomposite coatings were deposited by multi-arc ion plating under different bias voltages. The influences of bias voltage on composition, microstructure, surface morphology and mechanical properties of Cr–Si–N nanocomposite coatings were investigated in detail. The HR-TEM, XRD, and XPS results confirmed the formation of nanocomposite structure of nanocrystalline of CrN embedded into the amorphous phase of Si3N4. The particle radius of CrN can be calculated from the half-width of the diffraction peak of CrN (200) and the value was about 20–60 nm. In addition, no diffraction peaks of CrSi2, Cr3Si, or Si3N4 were found in all the Cr–Si–N coatings. With the increasing of bias voltages from 0 to −200 V, the number and size of large droplets on the coating surface decreased, and the growth mode of the coatings changed from loose to dense. However, with the increasing of bias voltages from 0 to −200 V, the micro-hardness of the coatings increased and then decreased, reaching its maximum value at negative bias voltages of 100 V. It was found that the friction coefficient of Cr–Si–N coatings is almost the same except for the Cr–Si–N coatings deposited under bias voltage of 0 V. When the oxidation temperature was at 800 °C, the Cr–Si–N coating was only partially oxidized. However, with the increase of oxidation temperature to 1200 °C, the surface of the coating was completely covered by the oxide generated. The results showed that the bias voltages used in multi-arc ion plating had effects on the structure, mechanical, and high temperature oxidation resistance properties of Cr–Si–N nanocomposite coatings.

MnxCo3-xO4 spinel coatings: Controlled synthesis and high temperature oxidation resistance behavior

A controllable method for the synthesis of MnxCo3-xO4 (x = 0.4, 0.8, 1.0, 1.2) spinel coatings with unique microstructures and high-temperature oxidation resistances for solid oxide fuel cells is crucially desired. Herein, we report the synthesis and analysis of synthesized coatings with different phase compositions of ferritic stainless steel interconnects. The coatings are fabricated using a sol-gel dip-coating method. Multiple experimental results confirm that the MnxCo3-xO4 coatings exhibit the advantages of having fine grains and uniform density. Furthermore, the as-prepared Mn1.2Co1.8O4 coating has a low coefficient of thermal expansion (11.98 × 10-6 K-1), matching that of ferritic stainless steel, which effectively improves the anti-stripping property of the materials. In particular, oxidation tests illustrate that the oxidation weight gain of this coating decreased by 84.4% compared with bare ferritic stainless steel after 3600 h. The area-specific resistance (ASR) results indicate that the ASR value of the Mn1.2Co1.8O4-coated sample reduced by about 70% compared with those of the ferritic stainless steel samples, which demonstrates its desirable high-temperature oxidation resistance property. It is hoped that this work stimulates new research ideas for the development of spinel oxide coating.

Preparation and high temperature oxidation behaviors of TiO2/Al2O3/Inconel625 composite coatings on the surface of Q235 alloy at 900 °C

Sol-gel method combined with plasma surfacing was used to prepare TiO2/Al2O3/Incone1625 composite coatings on the surface of Q235 alloys. Oxidation thermodynamic results show the composite coatings caused lower oxidation weight gain than the sample with single coating. Combination of XRD and SEM results illustrates that the surface and cross-sectional morphology were composed of an innermost continuous but not compact enough Cr2O3 layer, the outer layer next to C2O3 was loose and cracked NiO, and the outermost layer was composed of iron oxides for the Incone1625 coated sample. For the composite coating sample, the oxide film was composed of NiO as the outermost layer, Cr2O3 as the inner layer, there was a very thin but continuous layer consisted of Cr2O3 and Al2O3 as the innermost layer. This work shows that TiO2/Al2O3/Incone1625 composite coating improves the high-temperature oxidation resistance properties of the Q235 alloy at 900 °C by promoting the formation of the protective Cr2O3 and Al2O3 film.

Microstructure and high temperature oxidation resistance property of packing Al cementation on Ti-Al-Zr alloy

The aluminide coating was prepared on Ti-6Al-2Zr-1Mo-1 V titanium alloy by pack cementation to enhance the high temperature oxidation resistance for aircraft and aerospace applications. High temperature oxidation behaviors of packing cementation coated and uncoated titanium alloy samples were comparatively investigated by isothermal oxidation at 800 °C and 900 °C in air. The results show that the compact coating with about 60 μm thick was composed of TiAl3. With isothermal oxidation for 100 h at 800 and 900 °C, the weight gains of the coated samples are 1.29 mg·cm−2 and 4.06 mg·cm−2 respectively, which are about 2/5 and 1/5 of that of titanium alloy substrates (3.20 mg·cm−2 and 20.33 mg·cm−2). The excellent oxidation resistance performance is attributed to the formation of a continuous and dense Al2O3 layer on the TiAl3 coating surface, which was effective to prevent the O element diffusing into the coating and then reduce the oxidation rate.

Mechanical, tribological and oxidation resistance properties of Ni-based self-lubricating composite coatings at elevated temperature by APS

Abstract NiCrAlY-Mo-20Ag composite coating was fabricated by atmospheric plasma spraying. The influence of heat treatment on the mechanical properties, high temperature oxidation resistance properties and tribological properties of the coating were investigated. After 500°C heat treatment, the microstructure of the coating becomes more homogeneous and the amount of precipitated Y2O3 phase clearly increases. The micohardness and adhesive strength of the composite coating are effectively improved after heat treatment. The coating heat-treated at 500°C shows the highest micohardness and adhesive strength of 433.3 HV and 42.9 MPa as well as excellent lubricating properties over a wide range of temperature. Furthermore, the coating presents excellent oxidation resistance properties at 700°C and 800°C.

The Effect of Processing Parameters on the Formation and Properties of Al/Ni Core-Shell Pigments via a Galvanic Displacement Method

Al/Ni bimetallic core-shell pigments with flake Al particle as core and metallic Ni as shell were synthesized via a galvanic displacement method and studied with X-ray diffraction, scanning electron micrograph (SEM), specific surface area analysis (BET), thermogravimetry-differential thermalanalysis (TG/DSC), and visible-near infrared-infrared reflectance spectroscopy. The influence of reactant ratio (Al:Ni2+) and order of addition on phase structure, surface morphology, optical properties, and high temperature oxidation resistance properties were studied systematically. The results show that the local concentration of Ni2+ at solid-liquid interfaces can be effectively modulated by adjusting the reactant ratio and order of addition. A high local concentration of Ni2+ improves the rate of displacement reaction resulting in more metallic Ni on the surface of the flake Al powders. This increases the relative content of Ni in the shell. The change of displacement reaction rate also leads to a different surface morphology and roughness of the Ni shell. The thick and rough Ni shell has a strong absorption extinction due to the intense light scattering and absorption-this substantially reduces the spectral reflectance of the flake Al core. Infrared reflectance in particular is influenced by light scattering and absorption of the rough surface. In addition, the Ni shell can enhance the high temperature oxidation resistance of the Al core by preventing contact between the metallic Al substrate and oxygen. The oxidation resistance is also associated with the processing parameters of the galvanic displacement reaction.

Studies on nano-crystalline CoNiCrAlY consolidated by conventional and microwave sintering

The present study concerns mechanical milling of commercially available CoNiCrAlY powder to produce nanocrystalline CoNiCrAlY and its consolidation by conventional and microwave sintering techniques. Detailed studies were undertaken to understand the effect of processing history (conventional and microwave sintering), materials parameters (as-received and mechanically milled for different time), and process parameters (temperature and time of sintering) on the density, microstructures, composition and phase distribution, coefficient of thermal expansion and high temperature oxidation resistance property. The density of the consolidated product increases with increase in milling time; increase in temperature of sintering in both conventional sintered and microwave sintered samples, with a maximum density achieved due to microwave sintering. There is a significant reduction in coefficient of thermal expansion due to sintering with a maximum reduction occurred when sintering is conducted by microwave sintering. Isothermal oxidation study showed a significant improvement in oxidation resistance due to nano-crystallization with a maximum improvement observed for 48h milled sample microwave sintered at 1100°C for 48h.

Isothermal oxidation behavior of a thermal barrier coating prepared using EB-PVD

A novel two-layer structural thermal barrier coating (TBC) system with a ~150-µm-thick CoCrAlY bond coat (BC) and a ~60-µm-thick yttria stabilized zirconia (YSZ) ceramic top coat (TC) was prepared on superalloy K444 matrix using electron beam physical vapor deposition (EB-PVD). This deposited coating was characterized using isothermal oxidation tests (1000 °C × 200 h). The results indicated that the deposited coating had a dense structure and close bonding between the layers. The thermally grown oxide (TGO) layer (predominantly alumina) that formed at the interface between the TC and the BC as a consequence of the oxidation process was effective in preventing the further oxidation of the BC. In the later stages of the oxidation process, embedded oxides of chromium/cobalt were observed among the TC's columnar grains, and the TGO underwent densification thinning. Through observations of the growth behavior of the TGO, the element diffusion, displacement reaction, and volatilization of the oxides were found to be related to the weight loss in the coating and the densification thinning of the TGO. These coatings displayed superior high-temperature oxidation resistance properties. Copyright © 2014 John Wiley & Sons, Ltd.

Electrochemical extraction of Ti5Si3 silicide from multicomponent Ti/Si-containing metal oxide compounds in molten salt

Ti5Si3 silicide has been extracted directly from complex multicomponent Ti/Si-containing metal oxide compounds by electro-deoxidation in molten calcium chloride using an inert solid oxide oxygen-ion-conducting membrane (SOM) based anode. Studies on the microstructure evolution and electrochemical extraction mechanism show that the formation of Ti5Si3 and the removal of impurity elements happened simultaneously during the electro-deoxidation process. It is found that the electro-deoxidation generated Ti5Si3 micro-particles typically possess a smooth surface, which could contribute to create a continuous anti-oxidation surface layer with excellent high-temperature oxidation resistance property. Consideration is also given to the parameters of electrolysis and the electrochemical characteristics including chemical and/or electrochemical reactions during the electro-deoxidation process, and then a relevant kinetic model is proposed.

Development of MoSi2-SiC Component for Satellite Launch Vehicle

Intermetallic base MoSi2-SiC composite, an excellent high temperature oxidation-resistant material meant for the aerospace structural applications between 1600°C and 1700°C under oxidizing environment, has been developed successfully using powder metallurgy techniques. Mechanically milled (MM) MoSi2 powder, blended with SiC particulate was consolidated by vacuum hot pressing, yielded about 98.5% theoretical density. The composite has been characterized for physical, mechanical, and thermal properties. Properties were found satisfactory. Machining of semis to intricate shape was possible through electro-discharge machining (EDM) process. Plasma arc jet test (PAJT) under argon and argon + oxygen environment has proved its excellent high temperature oxidation resistance properties as it could sustain high heat flux up to 250 W/cm2 under oxidizing environment. The component realized has full potential to be used in critical aerospace application. This paper highlights the details of experimental work carried out and its characteristic properties attained.

Influences of Argon Ambience on Phase Composition and High Temperature Oxidation Resistance Property of Ceramic Coatings on Ti Alloy by Micro-Arc Oxidation

Abstract. Compound ceramic coatings with the main crystal phase of Al2TiO5 (as-coated samples) were prepared in situ on the surface of Ti-6Al-4V alloy by means of pulsed bi-polar micro-arc oxidation (MAO) in an NaAlO2 solution. The coated samples were calcined in argon and air at 1000 oC, respectively. The phase composition, surface and section morphology, and element contents of the ceramic coatings were investigated by X-ray diffractometry(XRD), Scanning electron microscopy (SEM) and X-ray fluorescence spectroscopy (XRF). The samples were treated in argon and the as-coated ones were calcined in air at 1000 oC to study the anti-oxidation properties of the samples. The results show that Al2TiO5 had been decomposed in an hour and transformed into α-Al2O3 and rutile TiO2 in air. However, Al2TiO5 had been decomposed in four hours in argon and the final coating surface was completely composed of α-Al2O3. The content of Al2O3 was decreased from outside to inside layers and Ti2O3 was formed in the coating. Furthermore, the morphology of the ceramic coatings after the calcination was different. The coatings calcined in argon were finer; the grains and pores were smaller than those in air. The high oxidation reaction of the TC4 substrate was the fiercest and the weight gains of the coated samples treated in argon was the lowest. The weight gains of the ceramic coatings were nearly changing in the form of parabola law.

Influences of Calcination Ambiences on Phase Composition and High Temperature Oxidation Resistance Property of Ceramic Coatings on Ti–6Al–4V Alloy by Micro-Plasma Oxidation

Compound ceramic coatings with the main crystalline of Al2TiO5 (as-coated samples) were prepared on Ti-6Al-4V alloy by pulsed bi-polar micro-plasma oxidation (MPO) in NaAlO2 solution. The coated samples were calcined in Ar and air at 1000oC, respectively. The phase composition, morphology and element content of the coatings were investigated by XRD, SEM and XRF. The samples treated in Ar and the as-coated ones were calcined in air at 1000oC to study the oxidation resistance of the samples. The results showed that Al2TiO5 decomposed and transformed into corundum and rutile TiO2 during the high temperature calcination. Al2TiO5 decomposed very quickly in air and the proportion of Al2O3 to TiO2 was 44:55 after a complete decomposition. On the contrary, Al2TiO5 decomposed very slowly in argon with the final proportion of Al2O3 to TiO2 of 81:18 on the coating surface. The morphology of the ceramic coatings after the calcination was also different. The coatings calcined in argon were fined: the grains and pores were smaller than those of the coatings calcined in air. The weight gains of both coatings changed in the form of parabola law, and the weight gains of the coated samples treated in argon were comparatively lower than that of the as-coated samples. During the high temperature calcination, the samples treated in argon cannot distort easily, compared with the as-coated ones.

Effect of trivalent rare earth dopants in nanocrystalline ceria coatings for high-temperature oxidation resistance

Nanocrystalline ceria (NC) and La 3+-doped nanocrystalline ceria (LDN) particles synthesized by the micro-emulsion method were coated onto AISI 304 stainless steel (SS) in order to study their high-temperature oxidation resistance properties at 1243 K in dry air for 24 h. Results were compared with those for micro-ceria (MC) coatings. The coated samples showed 90% improvement in oxidation resistance compared to uncoated and MC coated steels as seen from SEM cross-sectional studies. X-ray diffraction (XRD) analysis showed the presence of chromia in both NC and 20 LDN (NC doped with 20 at.% La 3+) samples which is absent in uncoated steels. From secondary ion mass spectrometry (SIMS) depth profiles, Fe, Ni depletion zones were observed in LDN-coated samples, indicating diffusion through the oxide layer. The role of oxygen vacancies in the nanoceria coatings on the formation of protective chromia layers is discussed.