High-temperature Resistance Research Articles

Preparation and characterization of novel lightweight Y2Si2O7 fibrous porous ceramics for high temperature thermal insulation

Fibrous porous ceramics play a vital role in the field of thermal protection systems. In this work, novel lightweight Y2Si2O7 fibrous porous ceramics were successfully prepared based on Y2Si2O7 fibrous membranes by molding method. The effects of mechanical dispersion speed and heat treatment temperature on the properties of Y2Si2O7 fibrous porous ceramics were characterized. The results revealed that benefiting from the appropriate fiber length, the ceramics had a better performance at a mechanical dispersion speed of 4000 revolutions per minute. The density, shrinkage, and compressive strength of the ceramics increased, but the porosity decreased slightly with the increasing heat treatment temperature. The prepared Y2Si2O7 fibrous porous ceramics exhibited favorable properties like low density (0.37 g/cm3), high porosity (90.56%), good high-temperature resistance (∼1350 °C), and low thermal conductivity (∼0.12 W m−1 K−1 at 27 °C, ∼0.566 W m−1 K−1 at 1000 °C). These properties indicate that Y2Si2O7 fibrous porous ceramics could be a promising candidate as thermal insulation materials in high-temperature environments.

A high temperature resistance and hyper‐dispersed nanoparticle grafted by multi‐monomer via in‐situ polymerization: Preparation, characterization, and its imbibition performance

AbstractIn recent years, the excellent cleaning‐oil capacity of nanofluid has attracted extensive attention and it has been widely used in oilfields as an imbibition agent. To solve the poor dispersion stability of nanoparticles in high‐temperature and high‐salt reservoir, this paper has prepared a hyper‐dispersed nanoparticle, polymer grafted nanosilica (PNS) that is anti‐salt monomer and anti‐temperature monomer simultaneously grafting on the surface of nanosilica via in‐situ polymerization reaction. Its imbibition performance has been discussed. Results show that (1) The two monomers are all successfully grafted on the surface of nanosilica via optimization of in‐situ polymerization reaction conditions. This hyper‐dispersed nanoparticle has 14.5% final grafting rate, approximately 18 nm in particle size, and −41.2 mV of zeta potential; (2) PNS fluid has excellent dispersion stability and its grain size has no obvious change in 20 wt.% of NaCl or 4 wt.% of CaCl2 fluids at room temperature (25°C), as well as in 18 wt.% of NaCl or 4 wt.% of CaCl2 fluids at 130°C after 1 week; (3) Crude oil–water interface tension can be decreased and the hydrophilicity is significantly boosted by this PNS fluid. Meanwhile, the 10−3 mN/m of interface tension can be obtained and the contact angle of water phase is decreased to 12.8° by surfactant erucamide propyl hydroxysulfobetaine (EHSB) synergizing with PNS fluid; (4) Oil recovery efficiency replaced by PNS in surfactant fluid has reached 39.3%. That is mainly because the hyper‐dispersed nanoparticle provides a stronger spreading force to enhance the efficiency of cleaning oil.

A Review of Research Progress on Ti(C,N)-Based Cermet Binder by Intermetallic Compounds and High-Entropy Alloys.

Ti(C,N)-based cermet is a kind of composite material composed of a metal binder phase and a Ti(C,N)-hard phase, which is widely used in the fields of cutting machining and wear-resistant parts due to its high hardness, good toughness, wear resistance, and chemical stability. In recent years, the research on the replacement of traditional Ni, Co, and Fe binder phases by novel binder phases such as intermetallic compounds and high-entropy alloys has made remarkable progress, which significantly improves the mechanical properties, wear resistance, corrosion resistance, and high-temperature oxidation resistance of Ti(C,N)-based cermets. This paper reviews the latest research results, summarizes the mechanism of the new binder to improve the performance of metal-ceramics, and looks forward to the future research directions.

SiO2 bridged AlN/methylphenyl silicone resin composite with integrated superior insulating property, high-temperature resistance, and high thermal conductivity

A high-temperature-resistance insulating layer with high thermal conductivity is the key component for fabricating the instant metal-based electric heating tube. However, it is still a challenge for materials to possess excellent high-temperature resistance, superior insulating property, and high thermal conductivity at the same time. Here, a novel SiO2 bridged AlN/MSR composite based on methylphenyl silicone resin (MSR) and AlN filler was reported. MSR with a high thermal decomposition temperature of 452.0 °C and a high withstand voltage of 5.6 kV was first synthesized by adjusting the contents of alkyl and phenyl groups. The superior high-temperature resistant insulating property is 3.7 and 2.4 times higher than the national standard requirement of 1.5 kV and commercial silicone resin, respectively. The hydrogen bonds formed between SiO2, AlN, and MSR and the electrostatic adsorption between SiO2 and AlN can remarkably improve the uniform dispersion of AlN in MSR and thus enhance the insulating property, thermal conductivity, and thermal stability. With the addition of 2 wt% SiO2 and 50 wt% AlN, the SiO2-AlN/MSR composite exhibits an extremely high withstand voltage of 7.3 kV, a high thermal conductivity of 0.553 W·m−1·K−1, and an enhanced decomposition temperature of 475 °C. The superior insulating property and thermal conductivity are 4.9 and 1.3 times higher than the national standard requirement and pure MSR, respectively. This novel composite shows great potential for application in the fields requiring integrated superior insulating property, high-temperature resistance, and high thermal conductivity.

Effect of epoxy value on the rheological properties and microcosmic mechanism of WER emulsified asphalt.

Waterborne epoxy resin (WER), a cleaning material with exceptional high-temperature resistance, has attracted much attention to modify emulsified asphalt in the pavement material field. Epoxy value is the critical characteristic index of WER. In this research, three WER with the epoxy values of 0.20 eq/100g, 0.44 eq/100g, and 0.51 eq/100g were utilized as asphalt modifiers. The influence of epoxy value on WER-EA was investigated by comparing the rheological properties of three kinds of WER emulsified asphalt (WER-EA). The modification mechanism of WER-EA has been analyzed using FTIR and SEM. The results demonstrate that different WER-EA resulted in significantly different rheological properties. WER-EA with the epoxy value of 0.20 eq/100g (E20) performed best at high temperatures, with a maximum increase of 17477% in G*/sinδ compared to the neat asphalt and a maximum increase of 66.3% in G*/sinδ compared to the other two WER-EA. WER-EA with 0.44 eq/100g epoxy value (E44) performed best at low temperatures, with a maximum increase in m value of 39.4% and a maximum decrease in S value of 33.3% compared to the other two WER-EA. In addition, the interpenetrating polymer network (IPN) in E20 was observed to be more solid and stable, and IPN in E44 was more uniform. To summarize, lower epoxy value led to a higher degree of WER reaction and higher content of rigid groups, which is more conducive to optimizing the high-temperature property of WER-EA. WER with moderate epoxy value resulted in a low content of polar bonds and thus high content of flexible segments, which helps emulsified asphalt to form a more uniform IPN.

Preparation of Ceramic Fiber Threads with Enhanced Abrasion Resistance Performance.

Ceramic fiber thread is one of the key components in flexible external thermal insulation blankets, and it has been applied in various fields as a flexible ceramic fibrous material with excellent deformability and high-temperature resistance. However, ceramic fiber threads are often subjected to reciprocating friction motion at specific bending angles, making them highly susceptible to abrade and fracture. Enhancing the abrasion resistance performance of ceramic fiber threads under bending conditions is the future trend and remains a significant challenge. Hence, we design and construct a novel polyurethane-modified coating on the ceramic fiber threads to improve their abrasion resistance performance. The effects of the types and concentrations of modifiers on the microstructure, abrasion resistance property, and tensile property of ceramic fiber threads are systematically investigated. The ceramic fiber threads, after modification with hexamethylene diisocyanate waterborne polyurethane (HDI-WPU) with a concentration of 3%, exhibit excellent abrasion resistance properties. The number of friction cycles at fracture of the modified ceramic fiber thread is more than three times, and the tensile strength is more than one and a half times, that of the original ceramic fiber thread, demonstrating the great potential of the HDI-WPU modifier for enhancing the abrasion resistance performance of ceramic fiber threads.

Enhancement of the Ablation Properties of Silica/Phenolic Resin Composites by SiC/Si3N4 Multiphase Structures

This work mainly studied the influence of SiC and Si3N4 composite fillers on the ablation performance of silica/phenolic composites. The effect of Si3N4 content on the mechanical and ablative properties of the composites was investigated, and the bridging effect between the two different ceramic fillers was analyzed. The results indicated that the mechanical properties and ablation properties of the composite were improved due to the combined effect of the SiC and Si3N4. When the content of Si3N4 was 36phr, the flexural strength at room temperature was 114.6 MPa, the flexural strength after 1200 °C treatment was 18.38 MPa, and the linear ablation rate was 0.011 mm/s in the 1600 °C oxyacetylene ablation test for 30s, while the flexural strength without Si3N4 at room temperature was 105.4 MPa, the flexural strength after 1200 °C treatment was 10.35 MPa, and linear ablation rate was 0.061 mm/s in the 1600 °C oxyacetylene ablation test for 30s. The bridges between the Si3N4 and SiC ceramic fillers can form SiO2, SiCN and Si2N2O in the high temperature environment, which helps fill the pores on the surface of the composite, forming an effective protective layer structure and improving the high temperature and erosion resistance of the composites.

Thermal analysis and microstructure evolution of TiC/Ti6Al4V functionally graded material by direct energy deposition

Metal/ceramic functionally graded materials (FGMs) have attracted significant attention due to their ability to combine the unique mechanical properties of metals with the high-temperature resistance of ceramics while mitigating the thermal stresses arising from the differences in their thermal expansion coefficients. In this study, the directed energy deposition (DED) technology is applied to manufacturing TiC/Ti6Al4V FGMs with TiC contenting up to 50 wt%. However, the variations in composition gradients and the complex thermal cycling processes lead to difficulties in the microstructure evolution and control. Therefore, a combined approach involving finite element (FE) simulations and experiments was employed to investigate the mechanisms underlying microstructural transformations under various gradient thermal cycles. The results showed that the morphology of TiC in the FGM from top to bottom is as follows: coarse dendritic TiC + unmelted TiC, granular primary TiC + underdeveloped dendritic TiC, chain-like eutectic TiC + granular eutectic TiC. Meanwhile, both α-Ti and β-Ti exhibited equiaxed transformation, with their sizes decreasing continuously with the gradient. This is due to the strong orientation relationship between TiC particles and the titanium matrix, allowing α-Ti and β-Ti to form non-uniform nucleation within the TiC phase. In addition, the chain-like eutectic TiC and dendritic primary TiC showed a certain degree of fragmentation and granulation after undergoing thermal cycling. The microstructural evolution mechanism in different gradient regions during the DED process under the coupling effect of thermal cycling and ceramic composition was clarified by combining the FE simulation results. The specimen at the bottom of FGMs exhibits strong and ductile (tensile strength: 1296 MPa, elongation: 7.17 %), which are mainly attributed to the Hall Petch strength and solid solution strengthening. The brittle phase of dendritic TiC and unmelted TiC under high gradients leads to decreased tensile properties.

Effect of non-metallic silicon content on the microstructure and corrosion behaviour of AlCoCrFeNi high-entropy alloys

AlCoCrFeNi high-entropy alloys (HEAs) have shown excellent mechanical properties and high-temperature oxidation resistance but poor corrosion resistance owing to the high contents of the aluminium passivation film. In this study, Si was added to these alloys with the aim of improving the composition and stability of the passivation films. The microstructure and corrosion behaviour of AlCoCrFeNiSix (molar ratio x = 0, 0.1, 0.2, 0.3, and 0.4) HEAs were investigated. Dendritic and spinodal decomposition regions were observed in all five alloys. In the dendritic region, the dendritic structures transitioned from a petal shape to a dendritic shape with increasing Si content. Phase separation occurred in the spinodal decomposition region, which predominantly consisted of ordered body-centred cubic (B2) and disordered body-centred cubic (A2) phases. The size of the A2 phase decreased, and the amount of the A2 phase increased with increasing Si content. An optimised Si content could enhance the stability of Al and Cr passivation films, whereas excessive Si imposed an adverse effect by forming a Cr passivation film. The corrosion resistance of AlCoCrFeNiSi0.2 HEAs was optimum with a passive current density of 3.2 μA/cm2, which was 0.2 times that of the obtained AlCoCrFeNi HEAs without Si. The type of corrosion changed from local corrosion of AlCoCrFeNiSix (x ≤ 0.3) HEAs to general corrosion of AlCoCrFeNiSi0.4 HEAs. The corrosion mechanisms of the AlCoCrFeNi HEAs with various Si contents were elucidated.

High-temperature oxidation behaviour of Ti65 titanium alloy fabricated by laser direct energy deposition

The study investigated the high-temperature oxidation behaviour of Ti65 titanium alloy fabricated by laser direct energy deposition (LDED). Results showed that the formation of multiple oxide layers (OL) better protected the matrix at 650 ℃, 750 ℃, and 850 ℃. The oxidation resistance improved with an activation energy of 282 ± 1.4 kJ·mol−1. A mathematical model to predict the relationship of oxidation was established through temperature-compensated time parameters, and it accurately predicted the oxidation mass gain and oxygen dissolution zone (ODZ) thickness. Ultimately, the mechanism of high-temperature oxidation resistance has been methodically elucidated.

Dynamic behavior of droplet impact on micro-nano structures with extreme wetting properties

Extreme wetting surfaces represented by superhydrophilic and superhydrophobic surfaces have important applications in heat transfer engineering such as boiling and condensation. The droplet impact behavior is helpful to deepen the understanding of extreme wetting characteristics and guide practical engineering applications. In this study, superhydrophilic and superhydrophobic micro-nano structures were fabricated by micro embossing and subsequent chemical treatment, and the droplet impact dynamics of microstructures, nanostructures, and micro-nano structures were analyzed using water and alcohol. Alcohol has the lower surface tension and wets the fabricated surfaces more easily than water. Among all fabricated structures, micro-nano multiscale structures exhibit the most extreme droplet impact dynamics. Whether it is water or alcohol droplets, the superhydrophilic micro-nano structures show the best spreading properties, and the maximum spreading factor (the ratio of the droplet wetting diameter to the initial diameter) of water is 134.1 % higher than the flat surface, which is also higher than both the microstructures and the nanostructures. Water droplets are more likely to bounce after impacting the superhydrophobic micro-nano structures than flat and nanostructures. However, due to the pinning effect of the larger-scale microstructures, the droplets impact on micro-nano structures would break and splash while the Weber number exceeds 43.41. The high-temperature impact dynamics show that the superhydrophobic micro-nano structures has excellent high-temperature resistance and can fully bounce within the tested range. The superior bouncing properties indicates the excellent condensation potential of the superhydrophobic micro-nano structures. The superhydrophilic micro-nano structures will be beneficial to enhance boiling heat transfer engineering applications, and the boiling heat transfer of droplets on the superhydrophilic micro-nano structures is the most severe during the boiling temperature range, and the drying time after alcohol impact is ∼ 63.4 % shorter than that of the superhydrophobic micro-nano structures.

Overview of Surface Modification Techniques for Titanium Alloys in Modern Material Science: A Comprehensive Analysis

Titanium alloys are acclaimed for their remarkable biocompatibility, high specific strength, excellent corrosion resistance, and stable performance in high and low temperatures. These characteristics render them invaluable in a multitude of sectors, including biomedicine, shipbuilding, aerospace, and daily life. According to the different phases, the alloys can be broadly categorized into α-titanium and β-titanium, and these alloys demonstrate unique properties shaped by their respective phases. The hexagonal close-packed structure of α-titanium alloys is notably associated with superior high-temperature creep resistance but limited plasticity. Conversely, the body-centered cubic structure of β-titanium alloys contributes to enhanced slip and greater plasticity. To optimize these alloys for specific industrial applications, alloy strengthening is often necessary to meet diverse environmental and operational demands. The impact of various processing techniques on the microstructure and metal characteristics of titanium alloys is reviewed and discussed in this research. This article systematically analyzes the effects of machining, shot peening, and surface heat treatment methods, including surface quenching, carburizing, and nitriding, on the structure and characteristics of titanium alloys. This research is arranged and categorized into three categories based on the methods of processing and treatment: general heat treatment, thermochemical treatment, and machining. The results of a large number of studies show that surface treatment can significantly improve the hardness and friction mechanical properties of titanium alloys. At present, a single treatment method is often insufficient. Therefore, composite treatment methods combining multiple treatment techniques are expected to be more widely used in the future. The authors provide an overview of titanium alloy modification methods in recent years with the aim of assisting and promoting further research in the very important and promising direction of multi-technology composite treatment.

Transcriptome Analysis Reveals Key Genes Involved in the Response of Pyrus betuleafolia to Drought and High-Temperature Stress.

Drought and high-temperature stress are the main abiotic stresses that alone or simultaneously affect the yield and quality of pears worldwide. However, studies on the mechanisms of drought or high-temperature resistance in pears remain elusive. Therefore, the molecular responses of Pyrus betuleafolia, the widely used rootstock in pear production, to drought and high temperatures require further study. Here, drought- or high-temperature-resistant seedlings were selected from many Pyrus betuleafolia seedlings. The leaf samples collected before and after drought or high-temperature treatment were used to perform RNA sequencing analysis. For drought treatment, a total of 11,731 differentially expressed genes (DEGs) were identified, including 4444 drought-induced genes and 7287 drought-inhibited genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that these DEGs were more significantly enriched in plant hormone signal transduction, flavonoid biosynthesis, and glutathione metabolism. For high-temperature treatment, 9639 DEGs were identified, including 5493 significantly upregulated genes and 4146 significantly downregulated genes due to high-temperature stress. KEGG analysis showed that brassinosteroid biosynthesis, arginine metabolism, and proline metabolism were the most enriched pathways for high-temperature response. Meanwhile, the common genes that respond to both drought and high-temperature stress were subsequently identified, with a focus on responsive transcription factors, such as MYB, HSF, bZIP, and WRKY. These results reveal potential genes that function in drought or high-temperature resistance. This study provides a theoretical basis and gene resources for the genetic improvement and molecular breeding of pears.

Easily constructed HNs/CNTs photothermal membrane with high-temperature resistance for efficient solar desalination and dye-polluted water purification

Utilizing abundant and renewable solar energy to produce clean freshwater from the existing seawater and wastewater has been considered a reliable and effective method to alleviate the severe shortage of freshwater currently. However, most of traditional desalination membranes usually showed insufficient photothermal conversion capacity, poor thermal stability, complex preparation procedure, and unsatisfactory water treatment efficiency. Therefore, we mixed as-prepared ultra-long hydroxyapatite nanowires (HNs) and carbon nanotubes (CNTs) for building HNs/CNTs membranes with high photothermal conversion efficiency, porous structure, high water transporting speed and remarkable high-temperature resistance in this work. Under one solar irradiation, the average light absorption of HNs/CNTs membrane was as high as 93%, and the evaporation rate of its integrated evaporator in simulated seawater (3.5 wt% NaCl) was 1.21 kg·m−2·h−1. Meanwhile, the HNs/CNTs membranes have good salt resistance and high Na+ removal rate, which makes their integrated evaporators suitable for solar-driven recirculation desalination process. Notably, the HNs/CNTs membranes also have excellent thermal stability, significant refractoriness and good thermal insulation, resulting in high temperature resistance and long-term solar evaporation stability. The water evaporation rate of HNs/CNTs integrated evaporator can be stabilized around 1.43 kg·m−2·h−1 and 3.74 kg·m−2·h−1 in 10 cycles of experiments under one and three solar irradiations. In addition, the removal rates of MB and RhB after photothermal purification via HNs/CNTs membranes reached up to 99.96% and 100%, respectively, displaying the promising and broad applications in solar desalination and dye wastewater purification.

Improving stress corrosion resistance and wear resistance of austenitic hot-stamping die steels via synergistic effects of shot peening and plasma nitriding

In this work, the effects of plasma nitriding, shot peening and their combination on the high-temperature wear resistance and stress corrosion resistance of an austenitic hot-stamping die steel were investigated. The results showed that the nitrided layer consisted of a single expanded austenite after nitriding at 560 °C for 4 h. Shot-peening pretreatment improved the surface hardness and depth of nitrided layer by 29.4 % and 36.4 % compared with the nitrided-only samples. This could be attributed to an increase in dislocation density, sub-crystal refinement, precipitation of nanoscale carbides and high strain of carbides and slip bands. Nitriding increased the stress corrosion resistance and high-temperature wear resistance of materials. Samples nitrided after shot peening showed the greatest wear and corrosion resistance. Besides, the introduction of residual compressive stresses in the nitrided layer by shot peening also improved wear and corrosion resistance to some extent.

Progress on the Properties of Ceramic Phase-Reinforced High-Entropy Alloy Composite Coatings Produced via Laser Cladding

The production of ceramic phase-reinforced high-entropy alloy composite coatings with excellent mechanical properties, high-temperature oxidation resistance, and corrosion resistance via laser cladding is a new hotspot in the field of surface engineering. However, as high-entropy alloys have a wide range of constituent systems and different kinds of ceramic particles are introduced in different ways that give the coatings unique microscopic organization, structure, and synthesized performance, it is necessary to review the methods of preparing ceramic phase-reinforced high-entropy alloys composite coatings via laser cladding. In this paper, the latest research progress on laser cladding technology in the preparation of ceramic phase-reinforced high-entropy alloy composite coatings is first reviewed. On this basis, the effects of ceramic particles, alloying elements, process parameters, and the microstructure and properties of the coatings are analyzed with the examples of the in situ generation method and the externally added method. Finally, research gaps and future trends are pointed out, serving as a reference for the subsequent research, application, and development of the preparation of ceramic phase-reinforced high-entropy alloy composite coatings.

Facile synthesis of UV-curable fluorosilicone polymers and coatings with good corrosive resistance on account of the reaction of disulfide bonds with vinyl groups

A new UV curing strategy is introduced into the curing field of fluorosilicone polymers. This strategy is predicated on the reaction of sulfur radicals generated from disulfide bonds with vinyl groups under the presence of UV light. Here, we engineered and synthesized a kind of novel fluorosilicone polymers (FS-SS) with disulfide bonds and vinyl groups. The disulfide bonds contained in FS-SS undergo photocleavage under ultraviolet irradiation, generating sulfide radicals, which can interact with vinyl groups to complete the curing reaction. Subsequently, the UV curing behavior of coatings on the basis of the novel polymers and photo-initiator 1173 was investigated by FT-IR spectroscopy and a possible UV-curable reaction mechanism based on disulfide bonds and vinyl groups was proposed. The results showed that curing reactions based on disulfide bonds and vinyl groups can reach a relatively high degree of reaction in a short period of time in terms of reaction rate. However, the lower conversion rate of the reaction may be due to the fact that the sulfur radicals generated by disulfide bonds are more inclined to form disulfide bonds rather than undergo addition reactions with vinyl groups. Subsequently, a series of fluorosilicone coatings with good optical transparency (transmittance above 90 %), good hydrophobicity (the lowest value of surface energy is 21.54 mN/m), lower roughness value (Ra values was in the region of 2.24 nm– 12.2 nm) and high temperature resistance were prepared by utilizing this curing strategy. Furthermore, the applicable experiment of fluorosilicone coatings to protect tinplate as anti-corrosive coatings was also performed. The corrosive resistance results formalize its practical value for possible application as preventive coatings.

Numerical simulation and experimental study on the preparation of the inner layer of bimetal composite pipe by high-frequency induction heating

Bimetal composite pipe has the advantages of impact resistance, low thermal expansion rate, pressure resistance and high temperature resistance. Its application scope is becoming more and more extensive, bringing more obvious economic, environmental and social benefits. In order to explore a new process for preparing bimetal composite pipe that is green, energy-saving and efficient. Ansys Workbench and Maxwell were used for joint simulation to obtain process parameters such as temperature distribution and thermal conduction time during high-frequency induction heating. Then the preparation of the bimetal composite pipe was completed through experiments, the forming quality and mechanical properties of the inner layer were tested and analyzed. The results show that process parameters have a significant impact on the molding quality of the inner layer. By optimizing the parameters, an amorphous inner layer with good molding quality, high hardness and high toughness was prepared, forming a metallurgical bond with the base pipe, with a bonding strength of 90.6 MPa. This research can provide a guidance for the preparation of bimetal composite pipe by high-frequency induction heating.

Gradient Cr–AlN composite coating prepared on alumina-forming austenitic steel

A gradient composite coating of Cr–AlN with an outer Cr-rich layer and an inner AlN-rich layer was deposited on the alumina-forming austenitic (AFA) steel surface by pack-cementation chromising. The phase composition, element distribution, and microstructure of the coating were characterised and analysed. The microhardness and the friction and wear performance at 600 °C were tested. The results show that the outer Cr-rich layer mainly consists of a polycrystalline Cr–Fe solid solution and a small amount of Cr2C and (Cr, Fe)2N1− x particles. The inner layer contains plenty of AlN particles with different sizes dispersed on the Cr–Fe solid solution. The formation of AlN particles is closely related to the spontaneous chlorination and nitridation reaction. The addition of Y2O3 particles in the encapsulated powder promotes the uniformity of Cr plating and the growth of AlN particles. The gradient composite coating remarkably improves the microhardness and high-temperature wear resistance of AFA steel.

Effect of dilution on the microstructure and high-temperature wear resistance of self-lubricating nickel alloy claddings

In this study, the impact of substrate dilution on the microstructure and tribological properties of tungsten inert gas (TIG)-deposited self-lubricating claddings was investigated. The dilution of Ti content on cladding increased as the TIG current increased, and the microhardness of the cladding decreased. The content of intermetallic phases such as TiNi and TiC increased with the increase in TIG current. The tribological studies revealed that coating dilution at higher TIG currents has prominent effects on wear behaviour at elevated temperatures. In both clads, the percentage decrease in hardness from higher TIG current to lower TIG current was noted as 31%. The higher dilution of Ti content in the cladding was found to be beneficial in tribological studies performed, especially at higher temperatures (≥400). Also, solid lubricants such as MoS2 and BaF2 encapsulation in the nickel alloy were found to be beneficial at both low and high temperatures.