Cyclic Thermal Shock Tests Research Articles

Phase transition heat storage and self-healing mechanism of spinel-calcium aluminate composite aggregate in corundum castable

Corundum-spinel castable is a vital refractory material used in steel ladle linings. Conventional approaches for assessing the thermal shock resistance of corundum-spinel refractory are not entirely representative of the actual application scenarios. This study investigates the influence of spinel-calcium aluminate composite aggregate on the thermal shock resistance of corundum castable using supersonic frequency induction heating technology. The research uncovers how CMA aggregate enhances the thermal shock resistance of corundum castable by cyclic thermal shock tests under varying operational conditions. Results reveal that the incorporation of CMA aggregate led to significant improvements in cold crushing strength and strength retention ratio following thermal shocks. The observed enhancement predominantly stems from the presence of CA/CA2 phase within the CMA aggregate, which undergoes a solid-liquid phase transition at high temperatures, enabling the absorption and retention of substantial heat and aiding in the repair of microcracks within the materials and at the interfacial regions.

The Influence of Cyclic Thermal Shocks at High Temperatures on the Microstructure, Hardness and Thermal Diffusivity of the Rene 41 Alloy.

The precipitation-hardenable nickel-based superalloy Rene 41 exhibits remarkable mechanical characteristics and high corrosion resistance at high temperatures, properties that allow it to be used in high-end applications. This research paper presents findings on the influence of thermal shocks on its microstructure, hardness, and thermal diffusivity at temperatures between 700 and 1000 °C. Solar energy was used for cyclic thermal shock tests. The samples were characterized using microhardness measurements, optical microscopic analysis, scanning electron microscopy coupled with EDS elemental chemical analysis, X-ray diffraction, and flash thermal diffusivity measurements. Structural transformations and the variation of properties were observed with an increase in the number of shocks applied at the same temperature and with temperature variation for the same number of thermal shocks.

THERMAL SHOCK BEHAVIOR OF LANTHANUM ZIRCONATE-BASED THERMAL BARRIER COATINGS

In this study, La2Zr2O7, Yb2O3 and Gd2O3-doped La[Formula: see text](Gd, Yb)[Formula: see text]Zr2O7 thermal barrier coatings have been manufactured from the crystalline and amorphous feedstock by plasma spraying. The thickness of the bond coat is 100±25 [Formula: see text]m and the thickness of the top coat is 250±25 [Formula: see text]m. Thermal shock tests were carried out in furnace temperature of 1200∘C. The thermal shock tests indicate that lifetime of the La[Formula: see text]Gd[Formula: see text]Zr2O7 coating has 55 cycles which is the highest thermal shock lifetime compared to other coatings in this study. The type of feedstock, amorphous or crystalline, strongly affects the thermal shock lifetime of La2Zr2O7 coatings. Coating damage after thermal shock tests was investigated using scanning electron microscope to observe the microstructure and X-ray diffraction techniques to analyze the phase composition. The failure of coatings is mainly in consequence of the accumulation of stress between bond coat–ceramic coat interface due to thermal expansion coefficient differences and thermally grown oxide layer formation during thermal shock cycling tests.

Research on the Application of Domestic High-Modulus Carbon Fiber/Epoxy Composites to Solar Panels for Solar Arrays

Based on the new high-modulus carbon fiber CCM40J-6k, which is the critical raw material of a solar panel, the molding process of a mesh face sheet combined with epoxy resin, the overall mechanical performance of a mesh face sheet combined with aluminum honeycomb, the compatibility with polyimide insulation film + solar cell circuit, and the space environment adaptability must pass a test verification and assessment as the premise for large-scale orbit applications. Therefore, based on the traditional carbon fiber M40JB-6k as a reference, a systematic verification project was conducted to apply the CCM40J-6k carbon fiber composite at the process, component, and assembly levels. Six aspects of testing and verifying items were conducted, including mechanical properties under room temperature and thermal shock conditions, bonding force of mesh nodes, comparison of the adaptability of domestic and imported carbon fiber substrates to high–low temperature alternation, the ability of domestic carbon fiber substrates to adapt to the thermal environment after laying solar cell circuits, and in-orbit lifespan of solar panels. Based on the verification results, the mechanical properties of the substrate are the same as those of the imported M40JB-6k, and the actual molding process for M40JB-6k can be utilized. Sample pieces of the substrates can withstand the thermal shock and thermal cycling tests. The bending stiffness of the sample pieces before and after the tests is 3.5%~9.6% higher, and the bending strength is 4.2%~7.2% lower. The tensile strength of mesh nodes made of domestic carbon fiber is 18.9% higher than that of mesh nodes made of imported carbon fiber. The CCM40J-6k substrate is similar to triple-junction GaAs solar cells. The change rates of the open-circuit voltage and the short-circuit current of solar panels based on domestic carbon fiber after fatigue thermal cycling with 2070 cycles are 0.55% and 0.24%, respectively. The above results indicate that the comprehensive performance of the domestic carbon fiber CCM40J-6k meets the requirements and can be applied to solar panels for solar arrays.

Investigating thermal shock and corrosion resistance of Inconel 601 super alloy after thermal barrier coating with %8 YSZ powder

Superalloys, which are categorized in three groups as iron-based, nickel-based and cobalt-based, are used especially in high temperature applications. Inconel 601 alloy, a nickel-based superalloy, is widely used in applications such as chemical processing, aerospace, power generation, heat treatment, chemical refining and gas turbine engines. Although the mechanical properties of superalloy materials and their resistance to wear, corrosion and oxidation are better than other metallurgical materials, these properties are not satisfactory in some applications. In such cases, the desired properties can be obtained by applying heat treatment and coating processes to superalloys. In this study, approximately 100, 200 and 300 µm ceramic top coat thickness thermal barrier coating system with NiCrAlY and 8%YSZ powder coating materials, were created for the Inconel 601 substrate material and SEM, EDS and XRD datas are given. Then, electrochemical corrosion test with 3.5% NaCl solution and 8 cycles of thermal shock test at 1200 °C using FCT thermal shock method were applied to the samples. Considering the corrosion rate values and SEM images after the electrochemical corrosion test, it was determined that the sample with the highest corrosion resistance was the sample with a ceramic top coating thickness of 100 µm. The reason for this is that as the coating thickness increases in thermal barrier coatings, the tension increases and accordingly, a change in pore and crack density occurs. The fact that the samples with a ceramic top coating of 100 µm thickness have the highest corrosion resistance can be explained in this way. Considering that the pore and crack ratio decreases due to the sintering effect in the SEM images of the samples after the thermal shock test, but considering that the TGO layer thickness will increase at higher temperatures and longer service conditions, in regards to thermal barrier coating deformation, it was concluded that the samples with 100 and 200 µm ceramic top coating thicknesses were safer in terms of thermal shock.

Thermal shock resistance and failure mechanisms of high temperature resistant radar and infrared compatible stealth coatings

The compatibility stealth coatings for aircrafts application have attracted widely concerns recently in aerospace engineering. In this work, the high temperature resistant radar and infrared compatible stealth coating (HRISC) system was prepared first, which mainly consisted of seven layers, such as low-emissivity layer, thermal barrier ceramic layer 1/2 (TBC1, TBC2), lossy layer, matching layer, etc. And then, the microstructures and thermal shock behaviors of HRISC system was determined. Results showed that the microstructures obviously changed after cyclic thermal shock tests. The horizontal cracks extended at the interface, leading to the matching layer and above detaching from the HRISC system after 70 thermal shock cycles. The numerical simulations showed that the interface of matching layer and TBC1 was under the highest stress state and prone to failure. In addition, the residual interfacial adhesion strength of the HRISC system after thermal shock tests was tested. The results showed that the failure position was at the interface between the matching layer and TBC1, and the interfacial adhesion strength decreased obviously with the increase of thermal shock cycles. All these can provide reference for the design and failure analysis of HRISC system in engineering application.

YAlO3 reinforced AlN composite ceramics with significantly improved mechanical properties and thermal shock resistance

AlN is regarded as a promising ceramic material for high performance structural and high temperature applications due to its superior properties such as high thermal conductivity, excellent stability and wear resistance. However, challenges remain in fabricating AlN ceramics with high strength and high thermal shock resistance. In this work, AlN/YAlO3 composites with different YAlO3 contents (3–10 wt%) were prepared by a simple pressureless sintering method, and the impact of YAlO3 content on mechanical properties and thermal shock resistance of AlN/YAlO3 composites was investigated. Results show that the grain growth of AlN is inhibited and the densification is improved with the addition of 3 wt% and 5 wt% YAlO3. Hence, the flexural strength and fracture toughness of AlN/YAlO3 composites are improved due to the grain refinement and compactness enhancement, and the highest value, 369 MPa and 3.84 MPa m1/2, are reached by the AlN-5 wt% YAlO3 composite. Moreover, the thermal shock resistance was assessed through theoretical forecast and cyclic thermal shock tests over a temperature range between 1000 °C and 1600 °C. Comparing with pure AlN, the thermal stress damage resistance parameters (RIV) of AlN/YAlO3 composites were increased, while their residual strengths and retention ratios after 10–50 cycles of thermal shock tests maintained a higher level as well. Microstructure analysis revealed that the thermal shock resistance of AlN/YAlO3 composites was evidently improved attributing to various strengthening mechanisms such as crack deflection, crack branching and microcrack toughening.

Cyclic Thermal Shock Response of Zirconia/304 Stainless Steel Functionally Graded Materials Fabricated by Centrifugal Slurry Methods

Functionally graded materials (FGMs) are multi-phase composites with gradual spatial variations of constituents. The compositional transitions in the FGMs are classified into two manners such as continuous gradient manners and stepwise manners. In this study, zirconia (ZrO2)/ 304 stainless steel (SUS304) FGMs with continuous gradient manners were fabricated by a combination of centrifugal slurry methods and spark plasma sintering (SPS). A variety of continuous gradient patterns were achieved by controlling the amount of dispersant such as ammonium polycarboxylic acid (PCA) in the slurry. With an increase in the amount of PCA, the gradient patterns in the FGMs changed from ceramic (ZrO2)-rich to metal (SUS304)-rich ones. According to Stokes sedimentation velocity simulations, the sedimentation velocity of SUS304 particles is higher than that of ZrO2 particles. With an increasing amount of PCA, the sedimentation velocity of the particles decreases. Cyclic thermal shock test results demonstrated that FGMs with metal (SUS304)-rich continuous gradient patterns showed the highest resistance among the samples of FGMs, 5-layered materials and ZrO2 single materials.

Cyclic thermal shock behaviors of carbon fibers reinforced SiCN ceramics with bio-inspired Bouligand-like architectures

Ceramic matrix composites (CMCs) are commonly used for high temperature components in aircrafts. However, thermal shock, as a typical loading case, will cause high thermal stresses in CMCs resulting in brittle fracture failure, and material cracking caused by thermal shock can further reduce the effectiveness of thermal protection function. In the present paper, we propose a bionic hierarchical fiber preform design method to improve the thermal shock resistance of ceramics. The effect of architectures of fiber preforms of continuous carbon fiber-reinforced CMCs on the thermal shock resistance was investigated to understand its importance and the related mechanical mechanisms. Thermal shock (cycling) tests were performed with continuous carbon fibers reinforced SiCN ceramic matrix composites (Cf/SiCN) prepared by PIP. 3D micro-CT scan and three-point bending tests were also conducted to evaluated the resultant damage. The results showed that smaller internal damage and higher thermal shock resistance can be obtained in comparison to pure SiCN ceramics, and the underlying mechanism can be explained by the fact that smaller pitch angle can resist the through-thickness crack propagation via promoting diffused in-plane damage. The present study offers a possibility in developing biomimetic Cf/SiCN ceramics with excellent thermal shock behavior.

Cyclic Thermal Shock Damage Behavior in CVI SiC/SiC High-Pressure Turbine Twin Guide Vanes.

In this paper, the SiC/SiC high-pressure turbine twin guide vanes were fabricated using the chemical vapor infiltration (CVI) method. Cyclic thermal shock tests at different target temperatures (i.e., 1400, 1450, and 1480 °C) in a gas environment were conducted to investigate the damage mechanisms and failure modes. During the thermal shock test, large spalling areas appeared on the leading edge and back region. After 400 thermal shock cycles, the spalling area of the coating at the basin and back region of the guide vane was more than 30%, and the whole guide vane turned gray, due to the formation of SiO2. When the thermal shock temperature increased from 1400 to 1450 and 1480 °C, the spalling area of the basin and the back region of the guide vane did not increase significantly, but the delamination occurred at the tenon, upper surface of the guide vane near the trailing edge of the guide vane. Through the X-ray Computed Tomography (XCT) analysis for the guide vanes before and after thermal shock, there was no obvious damage inside of guide vanes. The oxidation of SiC coating and the formation of SiO2 protects the internal fibers from oxidation and damage. Further investigation on the effect of thermal shock on the mechanical properties of SiC/SiC composites should be conducted in the future.

Thermal shock behavior under deuterium plasma exposure of tungsten–tantalum alloys

Tungsten–tantalum (W-Ta) alloys for the application to fusion reactor divertor were developed to overcome the issues of W related to the low temperature brittleness, embrittlement by recrystallization, and embrittlement by neutron irradiation. In the present study, the response to cyclic thermal shock tests as well as the fundamental mechanical properties of W-3%Ta and pure W were investigated, which simulated a transient heat load event in the actual divertor environment. Because it was concerned that the effect of deuterium (D) plasma exposure might be much more pronounced in the Ta-alloyed materials, the thermal shock tests were performed under the background steady state D-plasma exposure. Based on the present study, W-3%Ta might be a competitive alloy system from the viewpoint of thermo-mechanical response in the actual divertor environment as well as the fundamental mechanical properties and resistance to recrystallization.

Transferable, flexible white light-emitting diodes of GaN p–n junction microcrystals fabricated by remote epitaxy

The remote epitaxy of GaN p – n homojunction microcrystals (μCs) is demonstrated for fabricating transferable, flexible white light-emitting diodes (WLEDs). The GaN p – n junction μCs are randomly grown on graphene-coated Al 2 O 3 (0001), which are then delaminated for mass-transfer onto conducting copper tape. The μCs-LED shows electrical rectification and white electroluminescence (EL) emission. The μCs-WLED exhibits reliable LED performances after repetitive bending deformations and cycling temperature environments. Based on the transferability, the μCs-WLEDs are patterned and assembled to matrix arrays, which exhibit homogeneous, reliable performances even at a bent form. We discuss that the origin of white EL emission is mixing of blue and yellow–red EL emissions from p -GaN and n -GaN sides, respectively, based on photoluminescence spectroscopic measurements. This study opens a way of fabricating the transferable, flexible, and modular light panels through remote epitaxy. • Transferable, flexible white light-emitting diode (WLED) is demonstrated via remote epitaxy of GaN p – n junction microcrystals (μCs). • The WLED is reliably operated in repetitive bending deformation and thermal shock cycling tests. • Matrix arrays of WLED were easily assembled by transfer–printing method owing to excellent transferability endowed from remote epitaxy.

Modeling strain hardening during cyclic thermal shock tests of tungsten

An original model is proposed in order to simulate elastic-plastic transients inside tungsten subjected to cyclic thermal loads expected due to plasma instabilities called “edge-localized modes” in ITER. The model assumes that plasticity is achieved by thermally-activated dislocation motion and it accounts for both isotropic and kinematic hardening. Their relative contributions to the material response are tuned in order to reproduce uniaxial tensile tests performed at different temperatures and different strain rates in various tungsten grades. The model is designed for application as a user-defined material law in fully implicit finite element simulation of thermomechanical loads. The first predictions of the build-up of residual stresses are observed to be qualitatively in line with experimental trends.

Oxidation of boron-titanium thin film coating during cyclic tests on thermal shock

The results of experiments on cyclic thermal shock tests of promising neutronabsorbing titanium boride coatings are presented. It has been established that the main effect is the high-temperature oxidation of titanium boride with the formation of titanium and boron oxides. The regularities of changes in the oxidation parameters during cyclic thermal shock tests are determined.

Analysis of the brazing joints of tubular zirconia ceramics and 06Cr19Ni10 stainless steel tubes

ABSTRACT The gas-tight joining between yttrium-stabilised semi-closed zirconia ceramic tube and 06Cr19Ni10 stainless steel tube was achieved by using a self-made Ag–27Cu–4Ti paste filler material, where the joint form was an outer sleeve joint. After brazing, the samples were subjected to thermal shock (−50°C to 150°C) and thermal cycling tests (room temperature to 600°C), respectively. The sealing tightness of samples with different assembly clearances was investigated. Microstructure and phase composition of the joint with good performance was analysed. The results showed that the sealing performance of samples with the clearances of 0.03∼0.04 mm was best, and their tightness could still be less than 5 × 10−10 Pa·m3 s−1 after a series of heat treatment; microstructure of the joint with good sealing was dense and there were no obvious defects; the joining layer adjacent to ceramic was mainly comprised of three continuous reaction layers, the composition phase of which included Ti3Cu3O, TiO and ZrTiO4.

Reliability Assessment of Solder Joints in Electronic Devices Under Extreme Thermal Fluctuations

In this work, the effects of extreme thermal fluctuations on the reliability of solder joints were investigated. For this purpose, the solder joints in insulated-gate bipolar transistor (IGBT) devices were exposed to the conventional thermal cycling and the thermal shock cycling (TSC) tests. The finite element method (FEM) simulation results indicated that the accumulated creep energy in solder layer is much higher under the TSC process. Moreover, the stress triaxiality, as the indicator of damage initiation, is more concentrated in the TSC-exposed sample. It is believed that the higher heating and cooling rates along with the higher peak temperatures lead to the damage susceptibility of solder joints under TSC process. The experimental results confirm that the void formation and growth significantly increases in the TSC-exposed sample, which is consistent with the simulation outcomes. Moreover, the shear test reveals that the ultimate strength of sample under the thermal shocking severely decreases which is due to the void growth and the intensified elemental heterogeneity.

Anodic plasma electrolytic deposition of composite coating on ferrous alloys with low thermal conductivity and high adhesion strength

This work reports the preparation of oxide-based ceramic composite coatings as potential thermal barrier coatings (TBC) on ferrous alloys, targeting automotive applications. The coatings are shown to have excellent adhesion due to fabrication by plasma electrolytic aluminating (PEA), an anodic plasma electrolytic deposition process. The PEA process was conducted in an aluminate-containing aqueous electrolyte under a high voltage. The coating has superior adhesion (>60 MPa) and low thermal conductivity (~0.5 W/mK) measured by the adhesive tensile test and steady-state heat flow methods, respectively. Scanning electron microscope (SEM) observations reveal that the coatings have numerous mesopores. X-ray diffraction (XRD) analysis shows that the coating mainly consists of α-Al2O3 and hercynite (FeAl2O4) with (ultra-)fine grain size. Amorphous phases are also identified in the coatings. These mesopores, fine grain size and amorphous phases contributed to the low thermal conductivity of the coating. The hercynite phase indicated that the substrate was involved in the PEA reaction and thus the coating had a metallurgical bonding to the substrate. After cyclic thermal shock tests (quenching from 425 °C to 20 °C in water 100 times), the coating retained its porous structure without spallation. The results demonstrate that the ceramic composite coating may be a good candidate for thermal management of automotive engines.

Strengthening of DBA substrate with Ni/Ti/Ag metallization for thermal fatigue-resistant Ag sinter joining in GaN power modules

This study was carried out to develop a DBA (direct bonded aluminum) substrate with Ni/Ti/Ag metallization to achieve highly functional thermal shock stability of Ag sinter joining in GaN (Gallium Nitride) power modules. GaN /DBA die-attached module structures by Ag sinter joining was performed during harsh thermal shock cycling tests within a temperature range of − 50/250 °C. In the case of DBA without a Ni metallization layer (Ti/Ag), severe degradation occurred at the interface between the sintered Ag and Al due to significant plastic deformation of the Al layer. The shear strength decreased from an initial value of 33.1 MPa to 22.3 MPa after 500 cycles. With EBSD investigation, it was determined that the Al layer underwent sub-grain rotation recrystallization during thermal shock cycles. This led to a non-uniform grain orientation distribution at center and corner locations. On the other hand, Ni/Ti/Ag metallization showed that it can prevent severe Al deformation due to the superior rigidity achieved by Ni metallization. The die-shear strength maintained almost the same value as its initial value, even after 500 cycles. In addition, a numerical simulation analysis determined that the Ag sinter joining structure on the DBA substrate with Ni/Ti/Ag metallization had high functionality in stress relaxation. This study provided a novel approach to design thermal shock stability Ag sinter joining for next-generation power modules in high-temperature applications.

Utilization of aluminum dross: Refractories from industrial waste

Aluminum oxide (Al2O3) and Magnesium-Aluminum oxides (MgAl2O4) are well known refractory materials used in engineering industries. They are built to withstand high temperatures and possess low thermal conductivities for greater energy efficiency. Dross, a product/byproduct of slag generated in aluminum metal production process is normally comprised of these two oxides in addition to aluminum nitride (AlN). Worldwide, thousands of tons of aluminum dross are generated as industrial wastes and are disposed of in landfills causing serious environmental hazard. This paper explores the potential to synergize the characteristics of the favourable contents of aluminum dross and its availability (in tons) via synthesis of refractories and thereby develop a value added product useful for the modern industries. In this work, Al-dross as-received from an aluminum industry which comprised of predominantly Al2O3, MgAl2O4 and AlN, was used to develop the refractories. AlN possesses high thermal conductivity values and therefore was leached out of the dross to protect the performance of the developed refractory. The washed dross was calcined at 700° and 1000°C to facilitate gradual elimination of the undesired phases and finally sintered at 1500°C. The dross refractory pellets were subjected to thermo-physical and structural properties analysis: XRD (structural phase), SEM (Microstructure), EDS (chemical constituents) and thermal shock cycling test by dipping in molten aluminum and exposing to ambient (laboratory). The findings include the favourable prospects of using aluminum dross as refractories in metal casting industries.

Improving oil recovery from shale oil reservoirs using cyclic cold carbon dioxide injection – An experimental study

In this study, effects of injecting gas temperature and pressure on oil recovery factor (RF) of shale oil reservoirs were investigated by implementing cyclic cold carbon dioxide (CO2) injection on Eagle Ford Shale Oil core samples. Also, effects of injecting gas temperature on porosity, permeability, and brittleness indices of these core samples were assessed.An experimental setup was designed and built to implement CO2 cyclic gas injection and thermal shock tests. Four Eagle Ford Shale outcrop core samples were used in this study. The saturated samples were heated to 180°F and carbon dioxide at various combinations of pressure (1000 psi, 2000 psi, 3000 psi, and 4000 psi) and temperature (−15°F, 0°F, 32°F, and 74°F) was injected into them. Oil RF for each experiment was measured after five days of production period. Additionally, porosity, permeability and ultrasonic velocity of each core sample were measured both prior to and after conducting the experiment.The results indicate that injecting CO2 at low temperature results in higher oil recovery factor (up to 7%) than injecting carbon dioxide at ambient temperature. It was also observed that injecting cold CO2 enhanced both porosities and permeabilities of the core samples. The porosities and the permeabilities of the core samples enhanced by up to 3.5% and 8.8%, respectively. Also, a noticeable reduction (between 100 ft/s and 400 ft/s) in P-wave velocity was observed after injecting the cold gas into the core samples, which is an indication of creating induced fractures. The results also revealed that injecting the cold gas increased the brittleness indices of the core samples by up to 8. Hence, cyclic cold carbon dioxide injection could be potentially implemented in the shale oil fields to improve the efficiency of the current industry practice of cyclic gas injection technique.