High-temperature Behavior Research Articles

High-temperature corrosion behavior of 316 H stainless steel in lead-bismuth eutectic containing cesium

The influence of Cs on the corrosion of 316 H stainless steel pipework when exposed to liquid lead–bismuth eutectic (LBE) coolant, specifically LBE containing 0.5 wt% Cs at high temperature, is investigated. The addition of Cs in LBE can significantly accelerate the corrosion of 316 H stainless steel. Cs in LBE first destroys the Cr2O3 film on the surface of the stainless steel and reacts with Cr23C6 enriched at grain boundaries. Finally, the reaction between Cs and FeCr2O4 creates pores in inner oxide layer (IOL), thus destroying the protection provided to 316 H stainless steel by the IOL.

The high-temperature oxidation behavior and mechanism in a powder metallurgy Ni-based superalloy featuring δ-Nb3Al addition

The high-temperature oxidation behavior and mechanism in a powder metallurgy Ni-based superalloy featuring δ-Nb3Al addition

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.

A New Constitutive Model Based on Taylor Series and Partial Derivatives for Predicting High-Temperature Flow Behavior of a Nickel-Based Superalloy.

Ni-based superalloys are widely used in aerospace applications. However, traditional constitutive equations often lack the necessary accuracy to predict their high-temperature behavior. A novel constitutive model, utilizing Taylor series expansions and partial derivatives, is proposed to predict the high-temperature flow behavior of a nickel-based superalloy. Hot compression tests were conducted at various strain rates (0.01 s-1, 0.1 s-1, 1 s-1, and 10 s-1) and temperatures (850 °C to 1200 °C) to gather comprehensive experimental data. The performance of the new model was evaluated against classical models, specifically the Arrhenius and Hensel-Spittel (HS) models, using metrics such as the correlation coefficient (R), root mean square error (RMSE), sum of squared errors (SSE), and sum of absolute errors (SAE). The key findings reveal that the new model achieves superior prediction accuracy with an R value of 0.9948 and significantly lower RMSE (22.5), SSE (16,356), and SAE (5561 MPa) compared to the Arrhenius and HS models. Additionally, the stability of the first-order partial derivative of logarithmic stress with respect to temperature (∂lnσ/∂T) indicates that the logarithmic stress-temperature relationship can be approximated by a linear function with minimal curvature, which is effectively described by a second-degree polynomial. Furthermore, the relationship between logarithmic stress and logarithmic strain rate (∂lnσ/∂lnε˙) is more precisely captured using a third-degree polynomial. The accuracy of the new model provides an analytical basis for finite element simulation software. This helps better control and optimize processes, thus improving manufacturing efficiency and product quality. This study enables the optimization of high-temperature forming processes for current superalloy products, especially in aerospace engineering and materials science. It also provides a reference for future research on constitutive models and high-temperature material behavior in various industrial applications.

High-temperature erosion behavior of Al2O3 reinforced Inconel625 high velocity oxy-fuel sprayed and direct-aged composite coatings

In this study, Inconel625+30%Al2O3 (IN30AL) blended powders were sprayed on a commercially used boiler steel ASTM SA210 GrA1 using high-velocity oxy-fuel approach (HVOF). The microstructure, mechanical properties and elevated temperature erosion behavior of post-processed coatings and as-sprayed IN30ALcoatings were investigated. The elevated temperature erosion studies on IN30AL coatings both as-sprayed and post-processed were investigated at 900 °C temperature at two impact angles 30° and 90° using standard high temperature erosion test rig. Phase composition, interface of substrate/coating, and morphologies of eroded coatings were examined using x-ray diffraction, x-ray maps, scanning electron microscope, & energy dispersive spectrometer techniques. Compared with the as-sprayed IN30AL coatings, the heat-treated coatings have refined microstructure, better mechanical properties which improve the elevated temperature erosion resistance of IN30ALcoatings.

Effects of Y doping on phase structure, mechanical properties and sintering behavior of (Yb1-xYx)2SiO5 environmental barrier coating materials

Yb2SiO5 is one of the most widely studied environmental barrier coating materials due to its excellent high-temperature phase stability and resistance to water oxygen corrosion. In this paper, a series of (Yb1-xYx)2SiO5 (x = 0, 0.1, 0.2, 0.3, 0.4) ceramics were fabricated by high-temperature solid state sintering at 1550 °C. The effects of Y doping concentration on phase composition, mechanical properties, thermal conductivity and high-temperature sintering behavior of Yb2SiO5 ceramics were investigated in detail. The results show that all the (Yb1-xYx)2SiO5 ceramic specimens are composed of single X2-Yb2SiO5 phase with relative high compactness. The introduction of Y gives rise to the reduction of the thermal conductivity of Yb2SiO5 and the value of cell parameters and volume of (Yb1-xYx)2SiO5 is proportional to the Y3+ doping concentration. Among the five (Yb1-xYx)2SiO5 ceramics, (Yb0.9Y0.1)2SiO5 possesses the lowest brittleness index and its average fracture toughness is 2.85 MPa m1/2, which is about 10 % higher than pure Yb2SiO5. In addition, (Yb0.9Y0.1)2SiO5 has good high temperature phase stability from room temperature to 1450 °C and the grain size of (Yb0.9Y0.1)2SiO5 is basically unchanged after sintering at 1400 °C for 100 h. We believe that (Yb0.9Y0.1)2SiO5 is one of the most promising candidate materials for environmental barrier coatings.

Effect of Ag on High-Temperature Oxidation Behavior of Mg–6.5Gd–5.6Y–0.1Nd–0.01Ce–0.4Zr Alloy

Effect of Ag on High-Temperature Oxidation Behavior of Mg–6.5Gd–5.6Y–0.1Nd–0.01Ce–0.4Zr Alloy

Microstructure and high-temperature tribological behaviours of nano-HfC reinforced Inconel 625 composite coating by plasma-transferred arc welding

The study involved plasma arc transfer welding (PTAW) for preparing coatings of Inconel 625 alloys that contained different amounts of nano-sized hafnium carbide (nano-HfC) particles. The impact of nano-HfC on the microstructure evolution and mechanical properties of PTAWed Inconel 625 were investigated. The research reveals that nano-HfC decomposes during the high-temperature plasma arc process and then react with O element to generate nano-HfO2. These HfO2 can serve as nucleation sites for MC carbides, which restricts the growth of secondary dendrite arms, leading to a more disordered grain growth direction. Simultaneously, the decomposition of HfC can increase the C/Nb ratio of the matrix, effectively suppressing Laves phase formation while encouraging the development of MC carbides. Compared with IN625, the wear rate of composites at room temperature and 600 °C were decreased. Notably, at 600 °C, the wear rate of the coating with 0.5 wt% HfC is the lowest among all the samples, as reflected by a noteworthy reduction in wear rate of 50 %. This is mainly attributed to the refinement of γ matrix, reduction of Laves phase as well as precipitation of the fine-sized MC carbides. This work illustrates that adding nano-HfC is an effective way to improve the wear resistance of the PTAWed Inconel 625.

Effect of Ta on the high temperature oxidation behavior of Mo-based bulk metallic glasses

Mo-based bulk metallic glasses (BMGs) exhibited very high thermal stability and showed promising applications in high-temperature fields. However, their high-temperature oxidation resistance remains unsatisfactory. In this work, the effect of Ta (0–6 at.%) on the high-temperature oxidation behavior of MoCoB BMG was systematically investigated. The oxidation kinetics of MoCoB BMG and Ta-bearing Mo-based BMGs generally followed a parabolic law at 873–973 K, and the rate constants increased with the increasing temperature. The oxidation products of MoCoB BMG were primarily composed of CoMoO4 and MoO3, and the oxides of Ta-bearing Mo-based BMG were mainly CoMoO4, MoO3, CoTa2O6, and Ta2O5. The addition of Ta can significantly promote adhesion between the substrate and the external oxide layer, forming a dense spinel layer with a diffusion barrier that provides good oxidation resistance to the Mo-based BMG. The thin oxidation layer of Mo44Co34Ta6B16 was only about 13 μm after oxidation at 973 K for 120 h.

High-temperature tribological behavior of high-entropy sublattice oxide, nitride, and diboride coatings

The tribological performance of sputtered (Al,Cr,Nb,Ta,Ti)N, ▪ , and ▪ coatings on steel substrates was compared against TiN in dry ball-on-disk and scratch tests in ambient air at 20°C, 400°C and 700°C. The (Al,Cr,Nb,Ta,Ti)N and TiN perform similar in all tests, with (Al,Cr,Nb,Ta,Ti)N showing higher oxidation and abrasion resistance. The adhesion of (Al,Cr,Nb,Ta,Ti)N is superior to TiN at 20°C, but worse at elevated temperature due to an earlier onset of recovery processes that increase the mismatch in coefficient of thermal expansion with the substrate. The ▪ is the most abrasion resistant coating at room temperature owing to its high hardness, but suffers from oxidation in hot air. Scratch tests yield a similar adhesion strength to TiN at 20°C, but the anisotropic lattice expansion and shrinkage of the hexagonal structure at elevated temperatures lead to early delamination in the scratch test. The ▪ also adheres poorly on the steel, resulting in quick delamination during all tests.

Microstructure and mechanical response of as-built and solution-annealed LPBF Hastelloy X under high-temperature fatigue loading

This study investigates the microstructural characteristics and the high-temperature mechanical behavior of Hastelloy X, fabricated via laser powder-bed fusion (LPBF) technology. Hastelloy X, a solid solution-strengthened nickel-based superalloy known for its high strength and oxidation resistance at elevated temperatures, has gained significant interest for the fabrication of complex aerospace components through LPBF technology. The study initially focuses on the impact of solution annealing heat treatment at 1227 °C on the alloy microstructure, based on scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations. It then explores the fatigue and cyclic deformation response of the alloy at 750 °C across different strain ranges, comparing the as-built and solution-annealed conditions. To understand the observed differences in the cyclic mechanical response of as-built and solution-annealed LPBF HX, for a particular condition, a set of dedicated tests have been performed and interrupted at selected numbers of cycles in the different stages of the mechanical response. At each interruption point, specimens have been examined by TEM to provide an in-depth understanding of the effect of dislocation microstructural evolution on the high-temperature cyclic mechanical response of the alloy.

New lightweight high-entropy alloy coatings: Design concept, experimental characterization, and high-temperature oxidation behaviors

Lightweight high-entropy alloy (HEA) coatings by laser cladding (LC), which combines the advantages of high-entropy alloys and laser cladding, are potential materials for high-temperature applications. Al20Cr5Fe50Mn20Ti5 and Al25Cr20Fe20Mn15Ti20 HEAs were designed, and the calculated thermal parameters were close to the Ni-based alloy substrate (Inconel 718). Based on this, Al20Cr5Fe50Mn20Ti5 and Al25Cr20Fe20Mn15Ti20 HEA coatings were fabricated by LC on the substrates. The main phase structures of the two designed HEAs are the BCC + L21 phase, as revealed by the CALculation of PHAse Diagrams (CALPHAD). The high-temperature oxidation properties of the coatings were systematically investigated using isothermal oxidation tests. The oxidation activation energies of both coatings were 154.8 and 133.4 kJ/mol. Combined with molecular dynamics (MD) simulation, the clustering mechanism of Al and Ti elements was revealed in the formation of the L21 phase, whereas the high proportion of Ti elements increased the vacancy concentration, which was not conducive to oxidation resistance. Through this study, lightweight HEA coatings with excellent high-temperature performance can be designed and developed in the Al-Cr-Fe-Mn-Ti HEA system.

Study on the High-Temperature Mechanical Behavior and Parameters of Joints: a Case of a Prefabricated Frame Tunnel

Study on the High-Temperature Mechanical Behavior and Parameters of Joints: a Case of a Prefabricated Frame Tunnel

Evaluation of high-temperature oxidation behaviour of ATF claddings during severe accidents in nuclear power plants

This work aims to evaluate the oxidation behavior and kinetics of ADSS B#51 alloy in high-temperature air and to investigate the effect of the T-ramping rate on the kinetics of ADSS B#51. Using Thermogravimetric Analyzer (TGA), the high-temperature oxidation test was performed isothermally in air at 1000 °C, 1150 °C, and 1300 °C and for T-ramping tests at 1 °C/min, 4 °C/min, 40 °C/min. We estimated weight gains of the alloy in T-ramping condition and compared with measured value. It was concluded that the oxidation rates of the alloy during T-ramping were higher than those estimated by using parameters determined from the isothermal tests. In addition, surface oxide characterization using SEM-EDS demonstrated a complex surface oxide. Where the surface oxide and the oxide compositions were randomly distributed and not following any specific pattern. The findings showed that T-ramping oxidation kinetics parameters are in between the oxidation kinetics parameters of the steady-state region and transient region of isothermal oxidation, but closer to the transient region.

Role of heat treatment conditions in the high-temperature deformation behavior of laser-powder bed fused Fe–Cr–Ni–Al maraging stainless steel

The present research investigates the high-temperature behavior of laser powder bed fused (LPBF) Fe–Cr–Ni–Al maraging stainless steel (equivalent to PH13–8Mo). Fully dense PH13–8Mo samples are printed using an EOS M290 printer, and the effect of different heat treatments on high-temperature behavior and microstructure development is investigated. The material is studied under as-printed (AP), austenitized aged (AA, austenitized at 900 °C for 1 h followed by aging at 530 °C for 3 h), and direct-aged (DA, aged at 530 °C for 3 h) conditions. Uniaxial compression tests are conducted using a Gleeble® 3500 thermal-mechanical simulator at 400 °C and 500 °C at a quasi-static strain rate of 0.0001 s−1 to a final true strain of 0.2, while the microstructure characterization is performed using Electron Backscatter Diffraction and Transmission Electron Microscopy. At room temperature, the AA sample shows the highest hardness (strength), but at temperatures of 400 °C and 500 °C, the DA sample possesses the highest strength. Interestingly, the AP sample exhibits comparable strength to the DA sample at 500 °C, which could indicate for applications at these high temperatures, LPBF-PH13-8 Mo does not require any heat treatment.

Effect of hydrogen content on the high-temperature compressive deformation behavior and microstructure evolution of TC17 alloy

Thermo-hydrogen process (THP) has been an important research direction of the titanium alloy heat treatment process. However, the effect of THP on the thermal deformation behavior and microstructure evolution of TC17 alloy during hot compression has not been investigated. In this study, a series of isothermal compression experiments were carried out on hydrogenated TC17 alloy specimens in the temperature range covering the α+β phase region and β phase region of TC17 alloys with different hydrogen contents, to investigate the effect of hydrogen on the high-temperature flow behavior and microstructure evolution. The results show that the primary α phase of the hydrogenated TC17 alloy is significantly reduced. Observing the XRD pattern, the substitutional solution effect of hydrogen causes the β phase lattice to expand, resulting in a shift of the β phase toward a small angle as the hydrogen content increases. The flow stress shows a tendency to decrease and then increase with increasing hydrogen content. This is attributed to the softening effect of hydrogen on the α phase and the hardening effect on the β phase. This also leads to the deformation activation energy showing the same trend. When the hydrogen content increases to 0.4 wt%, the activation energy decreases to the lowest point by about 24 %. Finally, the appropriate hydrogen concentration can effectively reduce the destabilization region in the hot working map and expand the processing window of TC17 alloy.

High temperature oxidation behavior at 1250 °C: A new multilayer modified silicide coating design strategy on niobium alloys

Silicide coatings have proven to be promising for improving the high-temperature oxidation resistance of niobium alloy. However, the long-term protective property of single silicide coating remains a long-time endeavor due to the deficiency of oxygen-consuming phases, as well as the self-healing ability of the protective layer. Herein, a silicide-based composite coating is constructed on niobium alloy by incorporation of nano-SiC particles for enhancing the high-temperature oxidation resistance. Isothermal oxidation results at 1250 °C for 50 h indicate that NbSi2/Nb2O5-SiO2/SiC multilayer coated sample with a low mass gain of 2.49 mg/cm2 shows an improved oxidation resistance compared with NbSi2 coating (6.49 mg/cm2). The enhanced high-temperature antioxidant performance of NbSi2/Nb2O5-SiO2/SiC multilayer coating is mainly attributed to the formation of the protective SiO2 self-healing film and the high-temperature diffusion behavior of NbSi2/substrate.

Microstructure and mechanical behaviors of electron beam melted Ta10W alloy

TaW refractory alloys with excellent high-temperature mechanical behaviors up to 2000 ℃ have been intensively researched recently. Such performances herald great potential in industrial applications. In this study, we manufactured a Ta10W refractory alloy using selective electron beam melting with elemental TaW powder. The as-received microstructure shows high chemical homogeneity, and the obtained hardness values are 295±3 HV and 293±3 HV for XOY and XOZ planes, respectively. The yield strength of the compression tests can reach 664±8 MPa. The yield strength, ultimate tensile strength, and strain after fracturing of samples normal to the build direction of the as-deposited Ta10W refractory alloy are 750±5 MPa, 764±4 MPa, and 6.05±2.34, respectively. This study comprehensively investigated the microstructure and mechanical behaviors of the additively manufactured Ta10W refractory alloy, which can provide considerable insight into additive manufacturing of high-melting point refractory alloys.

High-temperature dynamic failure behavior and compressive mechanical properties of alumina porous ceramic with various pore sizes

The dynamic compressive mechanical properties of alumina porous ceramic with various average pore sizes are tested at strain rates and temperatures ranging from 0.01 s−1 to 2900 s−1 and 20 °C to 850 °C, respectively. The corresponding 3d Voronoi models are employed to simulate the meso‑characteristics of cells and failure characteristics of alumina porous ceramic in multiscale. The failure in macroscale of quasi-static compression is fragmentation, and that of dynamic compression is comminution. But in mesoscale, the failure, both of quasi-static and dynamic compression, is the fracture of cell walls. Its dynamic strength increases with the increase of strain rate, but decreases with the increase of temperature and average pore size. The increase in temperature and average pore size leads to a decrease in its strain rate sensitivity. Its Young's modulus is not sensitive to the strain rate, but increases with the decrease of average pore size, and decrease with the increase of temperature, which is presented as a temperature and average pore size dependent function. The strain rate and temperature effects are also presented by average pore size dependent functions, respectively. A constitutive model is proposed based on them. It shows that the constitutive model fits well with the experimental results.

Study on high-temperature erosive wear behaviour, surface roughness and scratch resistance of NiCrAlY-based composite coating

Study on high-temperature erosive wear behaviour, surface roughness and scratch resistance of NiCrAlY-based composite coating