High Temperature Oxidation Properties Research Articles

Study of high-entropy oxide diffusion barrier and diffusion resistance mechanism in high-temperature protective coatings

In order to obtain high temperature protective coatings with low diffusivity, high entropy (HEA) as well as high entropy oxide (HEO) diffusion barriers were deposited between the NiCrAlY coating and the substrate by magnetron sputtering. These two coatings were subjected to constant temperature oxidation tests at 1050 °C. These results show that the two coatings containing diffusion barriers have better high-temperature oxidation properties compared to the NiCrAlY coating. Both HEA and HEO diffusion barriers have the desired performance in hindering the diffusion of elements between the coating and the substrate. The evolution of these two diffusion barriers and the mechanism of diffusion resistance during the oxidation process have been investigated.

Enhanced Mechanical Properties and Wear Resistance of FeCrAl Alloys at ~ 300°C and Higher Temperatures

AbstractWorldwide, light water reactors (LWRs) have been using zirconium (Zr)-based alloys for the cladding of the uranium dioxide fuel for more than 6 decades. Zr alloys oxidize rapidly in the presence of water and steam at temperatures > 450°C; therefore, they do not respond well to scenarios of loss of coolant accidents. There is a global effort by nuclear materials technologists to find more robust or stronger cladding materials for LWRs. One option is to use an iron-chromium-aluminum (FeCrAl) alloy since they have excellent resistance to high temperature oxidation and superior mechanical properties at LWR operation temperatures. Results show that (1) FeCrAl alloys have better mechanical properties than Zr alloy and are orders of magnitude more resistant to creep at temperatures higher than LWR normal operation conditions. (2) FeCrAl alloys have better resistance to fretting wear than Zr alloys at the normal operation conditions of LWRs.

High temperature oxidation and thermal properties of laminated Ti3Al(Si)C2-TiC/Nb based composites obtained by spark plasma sintering

This paper describes high-temperature oxidation behavior and thermal properties of metal-ceramic laminated composites fabricated by spark plasma sintering of Ti3Al(Si)C2-filled preceramic papers (TAC) and Nb foils. The high-temperature oxidation tests were carried out in air at 800–1300 °C. The phase composition and microstructure of the oxide layers were analyzed by X-ray diffraction and scanning electron microscopy, respectively. The thermal properties were measured by the laser flash method in the temperature range of 30–800 °C. The evolution of the microstructure of the reaction layer (RL) formed at TAC/Nb interfaces was studied. The passive oxidation of the surface TAC layers results in the formation of outer TiO2 and inner continuous Al2O3 phase at temperatures up to 1100 °C, while local accelerated oxidation occurs above 1100 °C. As a result of breakaway oxidation, a multilayer oxide structure consisting of TiO2, Al2TiO5, Al2O3 and SiO2 phases were formed. The oxidation of inner Nb layers from the side surface can lead to high volume expansion and generation of stresses in the ceramic and metal layers due to the formation of Nb2O5 oxide phase. The stress relaxation occurred by complex mechanisms, including plastic deformation of the Nb layers, delamination at the interfaces, and formation of cracks in the reaction and TAC layers. The high temperature exposure results in slight increase in columnar grains in the reaction layers at 1200 °C, while the thickness of RL remains unchanged. The TAC/Nb composites exhibit higher thermal conductivity and diffusivity compared to monolithic TAC ceramic composites.

Mechanical, electrochemical corrosion, and high-temperature oxidation properties of stir-cast and heat-treated AZ80 magnesium alloy

This study aims to produce a stir-cast AZ80 magnesium alloy and to correlate the phases and microstructure of the as-cast, T4, and T6 conditions with the alloy's mechanical, corrosion, and oxidation properties. Microstructure was analysed using Field Emission Scanning Electron Microscopy (FE-SEM) with Energy Dispersive Spectroscopy (EDS), Electron Backscatter Diffraction (EBSD), and High-Resolution Transmission Electron Microscopy (HRTEM), and X-ray diffraction (XRD) technique was employed to examine at the alloy’s phases. A Vickers microhardness, tensile, and impact test specimens were meticulously prepared according to ASTM specifications. The electrochemical corrosion was tested in 0.6 M NaCl and 0.05 H2SO4, simulating the salty seawater and low-sulphur air environments. Based on the eutectic temperature of the Mg-Al alloy system, which is 437 ℃, the high-temperature oxidation test was carried out at 400 ℃, 410 ℃, and 420 ℃. Microstructural study confirms that both T4 and T6 alloys undergo grain coarsening with a grain size of 72.64 µm, and the orientation of the grains shifted from the pyramidal plane (2−1-10) to the basal plane (0001). The TEM investigation helps pinpoint the GP zone's genesis in T4 heat-treated AZ80. T4 AZ80 has a maximum ultimate tensile strength of 306 MPa and a ductility of 29.77% because of the dispersion-strengthening effect. The T6 AZ80, on the other hand, has a minimum corrosion rate of 0.158 mm/year in NaCl solution and an oxidation rate constant of 4.19 mg2.cm−4h−1 at 420 ⁰C. Notably, the T6 AZ80 shows significant peaks of Mg2Al3, and the as-cast shows more peaks of Mg17Al12. Magnesium alloy AZ80 is significantly affected by intermetallic phases like Mg17Al12 and Mg2Al3. The Mg2Al3 phase shows the latter tendency to resist corrosion and oxidation.

Effects of yttrium doping on high-temperature oxidation, friction, and wear properties of CrAlN films

This study investigates the deposition of CrAlYN nanomultilayer films with different yttrium (Y) contents on M2 tool steel and single-crystal Si wafer using unbalanced magnetron-sputtering ion-plating technology. Transmission and scanning electron microscopic and scanning morphologies, x-ray diffraction pattern, energy dispersive spectra, nanoindentation, high-temperature oxidation, and high-temperature tribological analyses show that CrAlYN nanomultilayer films have a face-centered cubic (fcc) crystal structure with a modulation period of CrN/YN+AlN/CrN/AlN. CrAlYN films exhibit optimal mechanical performance when Y content is 1.13at%. However, a substantial drop occurs when Y content increases to 2.67at%. As Y content increases, the high-temperature oxidation resistance, friction, and wear of CrAlYN films first increase and then decrease. Notably, films with the Y content of 1.13at% have optimal resistance to high-temperature oxidation, friction, and wear.

Microstructure, high-temperature corrosion resistance and oxidation properties of (TiVZrCrAl)N high entropy nitride coatings with different N2/Ar ratios

The (TiVZrCrAl)N high-entropy nitride coatings were prepared on Zr-4 alloy substrates by reactive magnetron sputtering with different N2/Ar pressure ratios I values. The microstructure, nanohardness, high-temperature corrosion and steam oxidation resistance properties of the coatings were investigated. The results showed that the thickness of the coating first decreaseds and then increaseds with decreasing N2/Ar pressure ratio, but the hardness first increaseds and then decreaseds. All the coatings exhibited B1-NaCl structure. When I = 1/12, the (TiVZrCrAl)N coating had excellent high-temperature corrosion resistance and steam oxidation performance. The high-temperature steam oxidation mechanisms of the (TiVZrCrAl)N coatings were analyzed in detail.

Microstructure evolution and EBSD analysis of multi-principal element alloy coatings after high-temperature oxidation

Multi-principal element alloy coatings (MPEACs) have great application potential for high-temperature diffusion barrier coatings. The sluggish diffusion and lattice distortion of this new coating material due to its own atomic size effect give the coating excellent resistance to high temperature oxidation and grain coarsening. In this study, the high-temperature oxidation properties, and microstructure evolution of quaternary, quinary, senary, and denary alloy coatings (whose lattice distortion magnitude is linearly increased) at 1100 °C were studied. The evolution of grain orientation, size, and grain boundaries of alloy coatings after high temperature exposure were analyzed by EBSD. The results showed that from quaternary to denary alloy coatings, with the rise in lattice distortion magnitude of the alloy system, the sluggish diffusion ability of the coating at high temperatures was more obvious. Specifically, the oxidative activation energy of quaternary to denary alloy coatings is 355.41, 480.96, 478.76, and 654.03 kJ/mol, respectively. A high distortion magnitude is beneficial to increase the activation energy of the alloy coating, as a result, grain growth of alloy coatings with high activation energy is significantly inhibited, and under the combined action of storage strain energy and solute dragging, the grain boundary migration rate of the coatings also declines. Finally, the denary alloy coating shows good resistance to high temperature softening. This study provides a positive reference for promoting the application of multi-principal alloys in diffusion barrier coatings.

Strengthening mechanisms and high-temperature oxidation properties of laser-clad TaNbZrTi refractory high entropy alloy coatings

Strengthening mechanisms and high-temperature oxidation properties of laser-clad TaNbZrTi refractory high entropy alloy coatings

High-Temperature Oxidation Properties of Ti-Hf-Mo-Ta-Nb-B Composite Coating Deposited on Ti60 Alloy with Laser Cladding

In order to improve the high-temperature oxidation resistance of Ti60 alloy, a Ti-Hf-Mo-Ta-Nb-B composite coating was prepared on Ti60 alloy with Ti, Hf, Mo, Ta and Nb powder and B powder as raw materials using laser cladding. The microstructure and oxidation behavior of the coating before and after oxidation at 1100 °C × 120 h in static air were studied with XRD, SEM, EDS and isothermal oxidation techniques. The results show that the coating was mainly composed of six phases, (Ti0.2Hf0.2Mo0.2Ta0.2 Nb0.2)B2, TiB, HfB2, Mo4.00 B3.40, TiHf and Hf1.86Mo0.14. The high-temperature oxidation of the coating and Ti60 alloy followed parabolic law, and the oxidation weight gain rate of the coating after 110 °C × 120 h was only 1/4.8 of that of the Ti60 alloy. The improvement of the high-temperature oxidation resistance of the coating may benefit from high-temperature oxidation resistance (Ti0.2Hf0.2 Mo0.2Ta0.2Nb0.2)B2, HfB2 and TiB boride ceramic phases.

Microstructure and High-Temperature Oxidation Properties of Nb2O5/TiO2 Composite Coatings Based on Ti6Al4V through Micro-arc Oxidation

Microstructure and High-Temperature Oxidation Properties of Nb2O5/TiO2 Composite Coatings Based on Ti6Al4V through Micro-arc Oxidation

Refractory high-entropy aluminized coating with excellent oxidation resistance and lubricating property prepared by pack cementation method

Refractory high-entropy alloys (RHEAs) exhibit superior mechanical properties at high temperatures compared to that of conventional high-temperature alloys. However, some refractory metallic elements are highly susceptible to oxygen absorption at room temperature and the resulting oxide films are not protective, resulting in catastrophic oxidation before they can exhibit excellent mechanical properties. Therefore, it is essential for them to improve the high-temperature oxidation properties of RHEAs. The pack cementation method can be used to prepare the aluminized coatings on the surface of RHEAs to improve their high-temperature oxidation resistance. In the present work, the aluminized high-entropy coatings were prepared on the surface of as-cast Ta25Nb25W25V25 RHEAs. The diffusion activation energy required for aluminization was experimentally calculated to be 137.667 kJ/mol, thus the growth kinetics of the coating was constructed. Aluminized coatings with the thickness of ∼75 μm and Vickers hardness of ∼680 HV0.01 obtained by holding at 1100 °C for 9 h were selected for the study. The oxidation activation energy of the aluminized coating at 800–1000 °C was 96.981 kJ/mol, while that of as-cast RHEAs was only 48.816 kJ/mol, so the oxidation resistance of the specimen was greatly improved. At 20–600 °C, the aluminized coatings also exhibited excellent wear resistance and lubrication properties. In particular, the average coefficients of friction were reduced by 0.13–0.24 compared to that of as-cast RHEAs, which can be attributed to the AlW intermetallic compound particles formed within the aluminized coating acting as self-lubricating particles.

Study on the Effect of Carburizing on the Microstructure and High-Temperature Oxidation Properties of Hot-Dip Aluminum Coating on Titanium Alloy

A Ti–Al alloy phase layer/Ti–Al carburizing composite coating was prepared on the surface of titanium alloy by the stepwise coating method of hot-dip aluminizing and then carburizing. The weight gain results of the composite coating showed that the titanium alloy coated with the composite coating had long-term stability (≥16 days) at 800 °C. The microstructure, phase structure, and composition of the composite coating were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The composite coating is composed of an alloy phase layer and a carburized layer. The natural transition of four phases (Ti3Al/TiAl/TiAl2/TiAl3) in the alloy phase layer significantly improves the interfacial bonding between the coating and the substrate and slows down the propagation of microcracks through the coating. Al2O3, TiC, and C in the carburizing layer improve the surface hardness of the coating, and TiAl2 and Al2O3 also have excellent oxidation resistance at high temperature.

High-temperature corrosion and oxidation properties of borided CoCrFeNiAl0.5Nb0.5 HEA

This study is focused on a detailed investigation of high-temperature corrosion and oxidation behavior of borided CoCrFeNiAl0.5Nb0.5 HEAs, considering their use in advanced engineering applications. CoCrFeNiAl0.5Nb0.5 HEA was produced by arc melting. XRD and SEM-EDS analysis before boriding determined that the alloy consisted of four different phases with different chemical compositions. Powder-pack boriding of a CoCrFeNiAl0.5Nb0.5 HEA was performed at 1000 °C for 3 h in a boriding media containing 90 % boron carbide and 10 % sodium tetrafluoroborate. As a result of the boriding process, complex boride layers consisting of (CoFe)B2, CrFeB, CoNbB, FeB and NiB phases were obtained on the surface with a thickness of 40 μm and hardness of 3004 HV. it was determined that the microstructure with cauliflower appearance evolved towards a dense and non-porous appearance around 20 μm as the boron diffusing into the HEA microstructure filling the gaps of intermetallic compound in the single structure, HEA and borided HEAs were each subjected to a cyclic hot corrosion test at 900 °C in molten corrosion salts of Na2SO4 and V2O5. After hot corrosion tests, long rod-like structures were observed in both samples due to the excessive corrosion, while borided alloys were more resistant to hot corrosion damage. After oxidation tests, HEA consists of a compact protective alumina scale that provided better oxidation resistance, while non-protective mixed oxides with cracks were dominant in the borided HEA.

High-temperature oxidation and wear properties of laser cladded Ti-Al-N composite coatings

Ti-Al-N composite coatings were in-situ synthesized on TC4 surfaces by laser cladding. The oxidation behaviors and wear properties of the as-obtained composite coatings and TC4 matrix were studied at various temperatures. The results showed the formation of a TiO2-dominated multilayer film on the composite coating surface at temperatures below 800 °C. The oxidation product of the coating contained a mixed oxide layer of TiO2 and Al2O3 at 900 and 1000 °C. The coatings exhibited good oxidation resistance at high temperatures. The thickening of the oxide film and distribution of the self-lubricating phase Ti2AlN in the coating decreased the friction coefficient to 0.2091. Also, the wear rate diminished to 0.025×10−4 mm3·N−1·m−1 at 800 °C, which is 1.43% that of the TC4 substrate. In the tested temperature range, the composite coatings showed mainly abrasive wear behavior, while an obvious lubrication effect was observed for oxide at high temperatures.

Construction of Cr coatings with different columnar structure on Zircaloy-4 alloys to optimize the high-temperature steam oxidation behavior for accident tolerant fuel claddings

To optimize the oxidation behavior of chromium-coated Zircaloy-4 alloys under 1200 °C high-temperature steam for accident tolerant fuel (ATF) claddings, Cr coatings with different columnar structure are constructed by changing bias voltage using high power impulse magnetron sputtering and corresponding microstructure, mechanical and high-temperature steam oxidation properties are studied systematically. With the bias voltage increase from 0 V to − 150 V, the microstructure of Cr coatings changes from porous columnar structure to compact columnar structure. Especial for bias voltage is − 90 V, the tiny compact grains uniform distribute on the surface micrographs and optimal compact columnar structure are observed on the cross-section micrographs. The hardness and elastic modulus of as-prepared Cr coatings increase firstly and then decrease, the hardness of Cr coatings with optimal compact columnar structure is 8.65 GPa, which is elevated ∼2.28 times than Cr coatings with porous columnar structure. 1200 °C high-temperature steam oxidation test results show an interesting phenomenon that the thickness of Cr layer reduces initial and then increase with the exposure time prolong from 1 h to 4 h. The main steam oxidation mechanism, in the early oxidation stage, is formation the compact Cr2O3 oxide layer. Then, with the exposure time extend, the reduction reaction plays the significant part for steam oxidation mechanism, which is consumption of outmost Cr2O3 oxide layer and formation of subsurface Cr layer. The construction of Cr coatings with compact columnar structure and relevant oxidation mechanism are expected to offer a new idea for improving 1200 °C steam oxidation resistance of chromium-coated Zircaloy-4 alloys.

High-temperature oxidation properties of economical and lightweight Fe-Cr-Ni-Al medium-entropy alloy

This study investigated the microstructure, high-temperature oxidation properties and mechanism of non-equiatomic Fe-Cr-Ni-Al medium entropy alloy (MEA). Microstructural observation of MEA identified coarse grains of mm scale, and cuboidal precipitates with an average size of 125 nm were evenly distributed within grains. Phase analysis confirmed that the alloy consisted of a Fe-Cr matrix (BCC structure) and B2 Ni-Al precipitate. High temperature isothermal oxidation tests measured oxidation weight of 0.08 mg/cm2 at 800 ℃, 0.17 mg/cm2 at 900 ℃, 0.22 mg/cm2 at 1000 ℃, and 0.47 mg/cm2 at 1100 ℃. Compared to other alloys tested with similar conditions, Fe-Cr-Ni-Al MEA presented by this study achieves economic benefits with relatively excellent high-temperature oxidation resistance. The outstanding high-temperature oxidation resistance of the MEA presented by this study is due to the evenly distributed dense stable Al2O3 layer formed regardless of temperature conditions. In addition, the alloy did not have breakaway oxidation, which can occur as oxidation progresses.

Effect of Nano Nd2O3 on the Microstructure and High-Temperature Resistance of G@Ni Laser Alloying Coatings on Ti-6Al-4V Alloy

Titanium and its alloys are widely used in high-end manufacturing fields. However, their low high-temperature oxidation resistance has limited their further application. Recently, laser alloying processing has attracted researchers to improve the surface properties of Ti, for which Ni coated graphite system is an excellent prospect due to its outstanding properties and metallurgical bonding between coating and substrate. In this paper, nanoscaled rare earth oxide Nd2O3 addition was added to Ni coated graphite laser alloying materials to research its influence on the microstructure and high-temperature oxidation resistance of the coating. The results proved that nano-Nd2O3 has an outstanding effect on refining coating microstructures, thus the high-temperature oxidation resistance was improved. Furthermore, with the addition of 1. 5 wt.% nano-Nd2O3, more NiO formed in the oxide film, which effectively strengthened the protective effect of the film. After 100 h of 800 °C oxidation, the oxidation weight gain per unit area of the normal coating was 14.571 mg/cm2, while that of the coating with nano-Nd2O3 addition was 6.244 mg/cm2, further proving that the addition of nano-Nd2O3 substantially improved the high-temperature oxidation properties of the coating.

Effects of deposition temperature on the microstructure, mechanical properties, high temperature corrosion and oxidation properties of AlCrNbTiZr high entropy alloy coatings

The AlCrNbTiZr high-entropy alloy (HEA) coatings with different deposition temperatures were prepared on Zr-4 substrate by magnetron sputtering. The effects of the deposition temperature on microstructure, mechanical properties, surface wettability, high temperature corrosion and oxidation resistance of coatings were systematically studied. The results show that the thickness of coating decreases first and then increases with the increase of deposition temperature. The coatings deposited at all temperatures is amorphous with BCC nanocrystalline domains, and the coating surface is hydrophobic. The room temperature (RT) deposition coatings have a high hardness of 25.41GPa, a good adhesion of 50 N and corrosion resistance compared with the coating at other deposition temperatures. The coating at RT deposited still has the ability to protect the substrate Zr-4 after the 1200 °C steam oxidation for 30 min. In addition, the corresponding steam oxidation mechanism is discussed in detail.

High Temperature Oxidation and Oxyacetylene Ablation Properties of ZrB2-ZrC-SiC Ultra-High Temperature Composite Ceramic Coatings Deposited on C/C Composites by Laser Cladding

In order to improve the high temperature oxidation and ablation resistance of C/C composites, ZrB2-ZrC-SiC ultra-high temperature composite ceramic coatings were prepared on C/C composites by laser cladding using Zr, B4C, and Si as raw materials. The microstructure of the coating was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Air isothermal oxidation (1600 °C, 80 min) and oxyacetylene flame ablation (2400 kW/m2, 300 s) were used to evaluate the high-temperature oxidation and ablation properties of the coating, respectively. The results show that the microstructure of laser cladding coating is a totem of black and white. The white part is mainly the first solidified high melting point ZrB2 phase, and the black part is the latter solidified eutectic structure, which is mainly composed of ZrB2(ZrB12)-ZrC or ZrB2(ZrB12)-SiC two phases. After oxidation at 1600 °C and 80 min, the coating is mainly composed of ZrO2 and ZrSiO4 phases, and ZrSiO4 is basically distributed among ZrO2 particles. The high temperature oxidation and ablation properties of the coating are better than the C/C composite matrix, and the mass ablation rate of the coating is about 1/4 of the latter.

High-temperature Oxidation Properties of TiC-reinforced Mo Matrix Composites with Cr Element Added

This work studied Mo-TiC-xCr (x = 0.0, 0.5, 1.0 wt.%) matrix composites with different component gradients prepared by Spark Plasma Sintering (SPS). The high-temperature oxidation test was conducted at 1200 ℃ in the atmosphere to study the influence of Cr on the high-temperature oxidation behavior of TiC-reinforced Mo matrix composites. The phase composition and morphology of the oxide film were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS), and the goal was to determine the effect of the Cr content on the high-temperature oxidation properties of the Mo-TiC-xCr (x = 0.0, 0.5, 1.0 wt.%) matrix composites. The results showed that with increasing oxidation time, the oxide film on the surface of Mo alloy will crack and fall off easily, and the porosity gradually increases. Oxygen underwent vigorous oxidation through the pores and the inside of the matrix, and a protective MoO2 internal oxide film disappeared. With increasing Cr content, the high-temperature oxidation performance of the Mo alloy improved, the thickness of the oxide film decreased, warping of the surface oxide film was inhibited, the porosity decreased, and volatilization of MoO3 was inhibited. After oxidation, the surface oxide film was mainly composed of TiO2, MoO3, Cr2O3 and Cr2(MoO4)3 phases. The TiC particles dispersed in the matrix were oxidized to TiO2 to inhibit the oxidation of the alloy. The Cr formed a protective oxidation film of Cr2O3, which effectively reduced the porosity and delayed the volatilization of the MoO3, thus improving its oxidation performance.