Excellent Thermal Shock Resistance Research Articles

Study of Glass-Ceramic Coating on the SUS430 Stainless Steel Plate with High Temperature Oxidation Resistance

Currently, the ceramic inner container draws great attention in the field of induction heating pot. Based on the traditional roll-forming process for ceramic pot, a new kind process was proposed to fabricate ceramic inner container and synchronously embed stainless steel plate by one-step high temperature sintering. The key technology for this process is to avoid the oxidation of SUS430 stainless steel plate during the high temperature sintering for a longtime by coating a glass-ceramic layer. In this research, the glass-ceramic coating with excellent high temperature oxidation resistance was optimized. The influences of ZrO2 content in the coating slurry on the high temperature oxidation resistance and thermal shock resistance of SUS430 stainless steel plate with glass-ceramic coating were studied. Meanwhile, the coatings were characterized by Scanning Electron Microscopy, X-ray Diffraction and Thermal Expansion Analysis. The experimental results showed that the glass-ceramic coating was smooth and had excellent thermal shock resistance when the addition of ZrO2 reached 15wt%. The mass gain of the SUS430 stainless steel plate with glass-ceramic coating was only 0.453% after sintering at 1300°C for 10h in air atmosphere, which was less one percent than that of SUS430 stainless steel plate under the same sintering condition.

Thermal Shock Behavior and Bonding Strength of MoSi<sub>2</sub>-BaO-Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> Gradient Porous Coating with Polymethyl Methacrylate Addition for Porous Fibrous Insulations

In order to improve the thermal shock behavior of high temperature resistant coating on porous fibrous referactory insulations, the MoSi2-BaO-Al2O3-SiO2(MoSi2-BAS) gradient porous coatings were designed by preparing a dense surface layer and a porous bonding layer with the method of brushing and subsequent sintering at 1773 K. The porous bonding layer was obtained by adding polymethyl methacrylate (PMMA) as pore former. As the content of PMMA increases, the MoSi2-BAS coatings changed from a dense structure into a gradient porous structure. The interface bonding strength and thermal shock resistance of the MoSi2-BAS coatings were investigated. The result shows that the as-prepared coating with gradient porous structure exhibited excellent thermal shock resistance, which remained gradient structure without cracking after thermal cycling 100 times between 1773 K and room temperature. And the interface bonding strength of the gradient porous coating reached 1.5±0.08 Mpa, which was much better than that of the dense coating.

A self-heating oxygen pump using microchanneled ceramic membranes for portable oxygen supply

A ceramic oxygen pump has been investigated as a potential self-heated oxygen generation device using electric potential as driving force. The required high temperature (around 748 °C) can be maintained locally on the membrane while the environmental temperature is kept at lower than 200 °C. The conventional dense membrane structure was found to be inappropriate for this application because it could not withstand the thermal shock induced by rapid heating and cooling. In contrast, the microchanneled membrane used in this work demonstrated excellent thermal shock resistance. It also demonstrated high Faraday efficiency when no electrode was coated on the microchannel surface. The Faraday efficiency exceeded 90% at 748 °C when 6.35 A cm−2 current density was applied. Under these conditions, an oxygen flux density of 20.6 ml cm−2 min−1 was achieved and this continued for 100 h without any degradation. Combined, these factors demonstrate that the microchanneled membrane can be potentially utilized within an oxygen generator having small size and good durability.

Hot Corrosion Behavior of Multilayered Titanium Aluminum Carbide/Yttria-Stabilized Zirconia Coatings for Silicon Carbide

Economic and environmental concerns are the main driving force behind the ever increasing demand for higher gas turbine engine inlet temperatures critical for meeting higher efficiency goals. Turbine materials, while in operation, are exposed to corrosive deposits of molten Na2SO4 produced from the high temperature reaction of environmental NaCl salt with sulphur resulting from fuel combustion. This phenomenon is known as “hot corrosion” and may lead to catastrophic failure of structural components. New light-weight and high-strength, high-temperature materials are needed to replace performance-limited metallic-based turbine components. Ceramic matrix composite (CMC) materials are attractive candidates for turbine hot-section components; however, direct exposure to combustion environments leads to degradation via corrosion, volatilization and associated surface recession. To protect against these phenomena, multilayered thermal and environmental barrier coatings are required to increase durability through cyclic operation to temperatures in excess of 1000°C. Mn+1AXn (abbreviated as MAX, where M is an early transition metal, A is an IIIA- or IVA-group element, and X is C or N) phases have received increasing attention because of their unique combination of properties including excellent thermal shock resistance and damage tolerance. Among them, Ti2AlC has attracted considerable interest because of its excellent high-temperature oxidation and hot corrosion resistance. Yttria Stabilized Zirconia (YSZ) is instead recognized as an efficient thermal barrier coating (TBC). The main objective of this study is to determine the effectiveness of a combined thin film coating (~5 μm) comprised of a MAX phase sublayer and a TBC top layer, specifically Ti2AlC coupled with YSZ. The thin film coatings were deposited via electron beam evaporation, physical vapor deposition (EB-PVD) on bulk SiC substrates used as prototypical material. Uncoated and coated samples were exposed to a simulated combustion environment gas mixture of air with 100 ppm SO2 after the deposition of 1 mg/cm2 of prototypical salt (Na2SO4) at 700 °C for up to 100 hours. The corrosion behavior of uncoated, Ti2AlC coated and Ti2AlC/YSZ coated samples were compared. Thermogravimetric analyses were performed to evaluate the development of the surface oxide layer in order to quantify the entity of the corrosion process. Results were then compared with those collected for samples exposed to simple oxidation conditions (air only). Phase compositions of coated and uncoated samples before and after exposure were assessed using X-ray diffraction (XRD) and their corresponding morphologies (surfaces and cross sections) analyzed with a scanning electron microscope (SEM) equipped with an energy dispersive x-ray spectroscopy (EDS) system. The corrosion mechanisms of the uncoated and coated specimens were proposed and compared based on the experimental results. Results and interpretations will be presented and discussed in the context of improving mechanistic understanding of hot corrosion behaviors of protective thin film coatings.

Effects of annealing on hardness and corrosion resistance of 60NiTi film deposited by magnetron sputtering

Difficulty in shaping and deformation impedes the application of 60NiTi alloy showing high hardness and high corrosion resistance. To promote the application of 60NiTi alloy, a 60NiTi film was deposited on 316 stainless steel substrate by magnetron sputtering. The results showed that a 60NiTi film with excellent adhesion property and excellent thermal-shock resistance could be prepared by sputtering at 1.5 A and then annealing at 500 °C. The hardness of annealed 60NiTi film was comparable to bulk 60NiTi alloy, and its corrosion resistance was much better than that of the bulk 60NiTi alloy.

Raw materials for manufacturing of Superior quality MgO-C bricks

In SAIL Plant, Magnesia carbon (MgO-C) bricks are used as lining material for Metallurgical Vessels like Steel ladles as well as Basic Oxygen Furnaces (BOF). MgO-C bricks are the most suitable refractory in these conditions for slag line as they possess superior slag penetration resistance and excellent thermal shock resistance at elevated temperature. In Iron & Steel Industry, manufacturing processes has changed significantly due to the rising demand of quality steel in the market. Furnace capacities have increased & technological parameters have changed. Plants have been modernized with addition of secondary steel making facilities to meet the stringent quality requirement of newer grades of steel.Refractories in steel ladle are subjected to severe operating conditions like high temperature (1670-1700°C) tapping of liquid steel from BOF, thermal shock, abrasion with molten metal due to stirring during gas purging, localized heating in slag zone due to arcing, corrosion with slag, thermo mechanical stress etc. Hence, use of superior quality refractory material with evenly distributed impurities is essential to get an end product of very high corrosion and spalling resistance and high thermo-mechanical properties. Easier application technique is also required for higher lining life with less down time. Various qualities of magnesia carbon refractories are used in different zones of steel ladles & BOF. Magnesia carbon refractories are essentially constitute of two highly refractory components i.e. magnesia and graphite.Sea water magnesia is mainly used in SAIL as the main raw material for manufacturing of magnesia carbon bricks. Fused magnesia has also been tried by partially mixing with sea water magnesia. Although MgO content in magnesia is important up to a certain level, but the type of impurities and their relative proportions plays vital role in achieving good performance. Besides chemical purity, bulk density and crystal size are considered to be very important properties of magnesia for application in BOF and steel ladles. Beside magnesia, graphite of both indigenous and import sources were used in different occasions. Purity of graphite has been reported to have great influence on slag corrosion resistance and hot properties of magnesia carbon bricks. Particle size distribution of graphite influences porosity and thermal shock resistance properties of magnesia carbon bricks.This paper deals with the properties of different raw materials for making of superior quality MgO-C bricks for improved performance in Metallurgical vessels of SAIL plants.

Straightforward Deposition of Uniform Boron Nitride Coatings by Chemical Vapor Deposition

ABSTRACTBoron nitride (BN) has a very high thermal conductivity and excellent thermal shock resistance. These properties make BN an important material for industrial applications involving surfaces in contact with molten metals. These applications require straightforward deposition methods that produce uniform BN coatings. Using borazine (B3N3H6) as a precursor, we deposited BN coatings on silicon substrates by cold-wall chemical vapor deposition (CVD). The microstructure, composition, and morphology of the coatings were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and electron energy loss spectroscopy (EELS). These characterizations show that the BN coatings deposited are uniform, predominantly of hexagonal structure, and N-rich.

Experimental Investigation of EDM Parameters for ZrB2-SiC Ceramics Machining

Ceramics ZrB2-SiC has been extensively applied in high temperature industry because of its high melting point, hardness, and excellent thermal shock resistance. However, ZrB2-SiC is difficult to machine with traditional cutting techniques due to its high hardness and brittleness. Electrical discharge machining (EDM) has been becoming one effective cutting technique to machine ZrB2-SiC components with high shape and dimension precision. In this paper, the process parameters including polarity of electrode, peak current, pulse-on time and pulse-off time are selected to study the influence on material removal rate, side gap, and surface roughness. Machined surfaces are analyzed using scanning electron microscopy (SEM), polygonal material layer and flat area are found on the machined surface. The forming of polygonal material layer is due to different thermal physical properties in the process of resolidification of ZrB2, SiC and pyrolytic carbon. The flat area is the central point of larger energy discharge channel. Tiny craters with few microns caused by removal of SiC grains are found on the machined surface, the number of them increases with increase of discharge energy.

A Robust CuCr2O4/SiO2 Composite Photothermal Material with Underwater Black Property and Extremely High Thermal Stability for Solar‐Driven Water Evaporation

AbstractThe design and fabrication of efficient photothermal materials is the key issue in solar‐driven water evaporation. In this work, a robust CuCr2O4/SiO2 composite membrane with outstanding solar‐driven water evaporation performance (1.32 kg m−2 h−1) under one sun irradiation is rationally designed and synthesized by using quartz glass fibrous membrane as supporting matrix and stable CuCr2O4 particles as the active light absorber. Instead of coating a separate layer on top of the support, the CuCr2O4 particles are evenly distributed inside the matrix, which endows the membrane with great mechanical strength and excellent wear and abrasion resistance. The highly porous composite survives 6 atm pressure and retains its performance even after 75% of the membrane is removed by sandpaper. This work also looks into a generally overlooked aspect of wet versus dry state of photothermal material and its implications. Interestingly, the composite possesses a gray color with a high reflectance in dry state but turns into deep black with a low reflectance in wet state due to the decreased subsurface scattering and strong NIR light absorbance of water in wet state. This composite material also possesses excellent thermal stability and thermal shock resistance, making it able to be easily recovered by calcination in air or direct burning in fire for contaminants removal. The results demonstrate that this composite is a competitive photothermal material for practical solar distillation and indicate that the optical properties of material in wet state are more relevant to photothermal material screening and optimization for solar distillation.

A promising non-transformable tetragonal YSZ nanostructured feedstocks for plasma spraying-physical vapor deposition

The nanostructured 8wt% yttria stabilized zirconia (n-8YSZ) feedstocks used for plasma spraying-physical vapor deposition (PS-PVD) were successfully prepared by the powder reconstitution method for the first time in this study. The n-8YSZ feedstocks were characterized by TEM, SEM and XRD. The results reveal that the grain size of n-8YSZ feedstocks is below 20nm and the particle size of spherical or equiaxed agglomerates is below 23µm. The n-8YSZ feedstocks are composed of only tetragonal prime (t´) phase. The t´ phase of feedstocks would bring excellent thermal shock resistance in the coatings. Hence, the n-8YSZ feedstocks will have a broader application prospect than the commercial M6700 powders whose main phase composition is monoclinic zirconia used for PS-PVD.

Mullite whisker toughened mullite coating to enhance the thermal shock resistance of SiC pre-coated carbon/carbon composites

In order to improve the thermal shock resistance of the coated carbon/carbon (C/C) composites, a mullite whisker toughened mullite coating was fabricated on the surface of SiC pre-coated C/C composites (SiC-C/C) by molten-salt method with a later hot dipping process. The phase compositions, surface and cross-section microstructures, high temperature thermal shock resistance of the as-prepared multi-layer coatings were investigated. Results show that the introduction of mullite whiskers can effectively improve the density of the mullite outer coating and decrease the cracking of the coating during the thermal shock cycle process. After 100 times thermal shock cycles between 1773K and room temperature, only 1.87 × 10−3gcm−2 weight loss has been detected, indicating the achievement of the excellent thermal shock resistance.

Preparation and characterization of high-performance ZrB2\u2013SiC\u2013Cf composites sintered at 1450 \xb0C

ZrB2–SiC–Cf composites containing 20–50 vol% short carbon fibers were hot pressed at low sintering temperature (1450 °C) using nanosized ZrB2 powders, in which the fiber degradation was effectively inhibited. The strain-to-failure values of such composites increased with increasing fiber content, and the value for the composite with 50 vol% Cf was even more than 3 times higher than that of the composite with 20 vol% Cf. Furthermore, the composite exhibited non-brittle fracture mode when the fiber content was above 30 vol%, and the thermal shock critical temperature difference of the composite with 30 vol% Cf was up to 727 °C, revealing excellent thermal shock resistance of this composite. Additionally, ZrB2–SiC–Cf composites displayed good oxidation resistance when the fiber content was below 40 vol%, suggesting that this method provides a promising way for preparation of high-performance ZrB2–SiC–Cf composites at low temperature.

Abrasive wear of ceramic wear protection at ambient and high temperatures

Ceramic wear protection is often applied in abrasive conditions due to their excellent wear resistance. This is especially necessary in heavy industries conveying large amounts of raw materials, e.g. in steel industry. Some plants also require material transport at high temperatures and velocities, making the need of temperature stable and abrasion resistant wear protection necessary.Various types and wear behaviour of ceramic protection are known. Hence, the goal of this study is to identify the best suitable ceramic materials for abrasive conditions in harsh environments at temperatures up to 950°C and severe thermal gradients. Chamottes, known for their excellent thermal shock resistance are compared to high abrasion resistant ceramic wear tiles and a cost efficient cement-bounded hard compound. Testing was done under high-stress three-body abrasion regime with a modified ASTM G65 apparatus enabling for investigations up to ~950°C. Thereto heated abrasive is introduced into the wear track and also preheated ceramic samples were used and compared to ambient temperature experiments.Results indicate a significant temperature influence on chamottes and the hard compound. While the chamottes benefit from temperature increase, the cement-bounded hard compound showed its limitation at abrasive temperatures of 950°C. The high abrasion resistant wear tiles represented the materials with the best wear resistance and less temperature influence in the investigated range.

Non-Isothermal Reaction Kinetics Study of MgO-C Refractories with Added Low-Ash Consent Graphite

Magnesia-carbon (MgO-C) is widely used in metallurgical furnaces due to its excellent slag thermal shock and corrosion resistance properties. Carbon is non-wettable by slag, which protects MgO, but oxidises in the presence of oxygen. An experiment was undertaken to investigate the oxidation resistance of MgO-C in non-isothermal conditions through evaluation of kinetic laws. MgO-C samples with 2,8% ash content graphite and resin binder were prepared and their oxidation behaviour with respect to weight loss was determined in a specially designed furnace. Samples were fired from 700 to 1400°C at heating rates of 3, 5, 7 and 9 K per minute. Their continuous weight loss was measured at 50 K intervals. In order to find the mechanism(s) associated with oxidation of MgO-C samples, a reduced time ‘∅’ plot analysis was carried out for the samples. For all temperatures and samples, the initial oxidation mechanism was observed to obeya chemical reaction-controlled second order chemical mechanism followed by diffusion processes at higher temperatures.

Microstructure, mechanical properties and thermal shock resistance of ZrB 2 -SiC-C f composite with inhibited degradation of carbon fibers

Abstract ZrB 2 -SiC-C f composite with carbon coated carbon fibers was successfully prepared by low temperature hot pressing. This composite showed an excellent thermal shock resistance compared with those composites fabricated by hot pressing and spark plasma sintering using as-received carbon fibers. Toughening mechanisms such as crack deflection, crack branching, fibers pull-out and fibers bridging were obviously detected in ZrB 2 -SiC-C f owing to the inhibited degradation of carbon fibers and the relatively weak fiber/matrix interfacial bonding, leading to a non-brittle fracture mode of the composite. Moreover, the composite exhibited an excellent thermal shock resistance with a high critical thermal shock temperature difference of 773 °C which is about twice those of the reported ZrB 2 -based ultra-high temperature ceramics. This work provides valuable guidance in the preparation of ZrB 2 -based ultra-high temperature ceramics with a combination of excellent properties.

High-performance ZrB2-SiC-Cf composite prepared by low-temperature hot pressing using nanosized ZrB2 powder

High-performance ZrB2-SiC-Cf composite was successfully prepared by low temperature (1450°C) hot pressing using nanosized ZrB2 powder. Such material exhibited a non-brittle fracture feature, high work of fracture (321J/m2) and excellent thermal shock resistance as well as good oxidation resistance. Composite incorporating carbon fibers in which the degradation of the carbon fiber was effectively inhibited through low-temperature sintering displayed remarkably improved thermal shock resistance with a critical temperature difference of 754°C, almost twice those of the reported ZrB2-based ultra-high temperature ceramics. The thermal and chemical stability of the carbon fiber and ceramic matrix were further analyzed by thermodynamic calculation and HR-TEM analysis.

Gradient structure high emissivity MoSi2-SiO2-SiOC coating for thermal protective application

This study presents a one-pot preparation of gradient porous high emissivity coatings on ceramic fibrous insulations. MoSi2-SiO2-SiOC coatings have been prepared on mullite fibrous substrates with polysiloxane-derived SiOC glass as low-temperature adhesive, SiO2 as high-temperature ceramic aggregate, MoSi2 as emission agent and polydimethylsiloxane (PDMS) as pore former by slurry-spraying, drying and sintering. Scanning electron microscopy shows the MoSi2-SiO2-SiOC coating gradually changes from a porous structure into a dense structure with obviously decreasing porosity from substrate to surface. The pore size and porosity of the bonding-layer increase with the PDMS content and the density of the surface-layer increases with the sintering temperature suggesting the gradient porous structure is formed by two-steps of “low-temperature decomposition pore-forming” and “high-temperature sintering pore-sealing” during sintering. Firstly, the pores come into formation after decomposition of PDMS and the organic-to-inorganic transformation of the SiOC glass at lower temperature (<1000 °C). Secondly, the formed pores are partly sealed accompanied by carbothermal reduction of the SiOC glass and carburization reaction of the MoSi2 at higher temperature (>1400 °C). The gradient MoSi2-SiO2-SiOC coating increases the bonding strength between the coating and substrate up to 0.6 MPa, which is nearly twice as high as that of dense MoSi2-SiO2 coating. The MoSi2-SiO2-SiOC coating exhibits high spectral emissivity (0.90 at 700 °C), excellent thermal shock resistance (90 cycles without cracking at 25–1500 °C) and oxidation resistance up to 1500 °C, all of which can meet requirements of high temperature application.

A review on the utilization of natural graphite and graphite-based materials

As a type of inorganic non-metallic resources, the natural graphite has a small thermal expansion coefficient (1×10−6–30×10−6 K), a high coefficient of thermal conductivity (129 W m−1 K−1), high temperature resistances, excellent electrical conductivity (resistivity 8×10−6–13×10−6 Ω m), brilliant lubricity with a friction coefficient of 0.08–0.16, plastic feature, good chemical stability, excellent thermal shock resistance and other properties, which makes it well-known as one of the “universal” mineral materials. Graphite has been widely used in the machinery, metallurgy, petrochemicals, light industry, electronics, electrical appliances, military defenses, aerospace and other economic fields. China is one of the countries that have the largest resources of natural graphite in the world. Based on data of the graphite mineral resources, production/consumption, and the international trade of China during the past several years, this paper gives an overview of the development of graphite mining, technologies in purifying raw ores, comprehensive utilization of graphite, applications and the technological innovations of graphite-base materials. The most important three types of graphite products including the expanded graphite, the fluorinated graphite, and graphene (2D graphite) are particularly reviewed. The production process based imported graphite products, technological innovation and the gap between China and developed countries are analyzed, and the development of the comprehensive utilization of graphite resources is introduced. Finally, the future direction of the graphite science was proposed according to the disciplinary development in the non-metallic mineral materials.

The analysis and fabrication of a novel tin-nickel mixed salt electrolytic coloured processing and the performance of coloured films for Al-12.7Si-0.7Mg alloy in acidic and alkali corrosive environments

We present for the first time the analysis and fabrication of a novel Tin-Nickel mixed salt electrolytic coloured processing and the performance of coloured films for Al-12.7Si-0.7Mg alloy. This alloy is a novel alloy containing high silicon aluminum alloy extrusion profile which presents excellent mechanical properties as well as broad market prospects. Nevertheless, this kind of material is urgent in need of surface treatment technology. The orthogonal design and single factor tests were applied to optimize for electrolytic coloured technological conditions. By controlling operation conditions, the uniform electrolytic coloured films with different color were obtained. Analysis of microstructure showed that tin particles had been deposited in the coloured film. The coloured films, about 10 μm thick, were uniform, dense and firmly attached to the substrate. After the coloured samples were maintained at 400oC for 1 h, or quenched from 300oC to room temperature, the coloured films did not change, demonstrating excellent thermostability and thermal shock resistance. Acid and alkali corrosion tests and potentiodynamic polarization showed that corrosion resistance of coloured sample was much better than those of untreated samples. After 240 h neutral salt spray test, protection ratings and appearance ratings of coloured films were Grade 9.

Preparation and characterization of amorphous SiO2 coatings deposited by mirco-arc oxidation on sintered NdFeB permanent magnets

Amorphous SiO2 coatings were prepared on sintered NdFeB magnets by micro-arc oxidation (MAO) in silicate solution. The surface and cross-sectional morphologies, element and phase composition, corrosion resistance and magnetic properties of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization test and physical properties measurements system (PPMS). The results showed that the surface morphologies of the coatings exhibited the “coral reef” like structure, different from the typical MAO porous structure. With increasing the voltages, the thickness of the coatings increased from 12.72 to 19.90µm, the content of Si element increased, while the contents of Fe, Nd and P elements decreased. The coatings were mainly composed of amorphous SiO2 and a few amorphous Fe2O3 and Nd2O3. The amorphous SiO2 coatings presented excellent thermal shock resistance, while the thermal shock resistance decreased with increasing the voltages. The corrosion resistance of the coatings increased with increasing the voltages, and it could be enhanced by one order of magnitude compared to the uncoated NdFeB magnets. The MAO coatings slightly decreased the magnetic properties of the NdFeB samples in different degrees.