Thermal Erosion Research Articles

Thermal erosion test of ZrB2-based ceramics

The thermal erosion of a set of bulk fully dense and 10% porous ZrB2-based ceramics of different composition were machined as sharp wing and tested in an air-fuel mixture flow formed by mixing air and kerosene with an oxygen content ~ 5wt%. The resulting pressure in the combustion chamber was 0.8MPa and the flow temperature was 1500°C. Microstructural analyses upon the tests evidenced that criteria for material success include high density and high thermal conductivity, along with formation of stable compounds. These results were supported by numerical simulation. Among all tested materials, only ZrB2-15 MoSi2 (ZM) ceramics met all the requirements and successfully survived the thermal erosion test up to 1200sec.

The cryostratigraphy of thermo-erosion gullies in the Canadian High Arctic demonstrates the resilience of permafrost

Abstract. Thermo-erosion gullies (TEGs) are one of the most common forms of abrupt permafrost degradation. They generally form in ice-wedge polygonal networks where the interconnected troughs can channel runoff water. Although TEGs can form within a single thawing season, it takes them several decades to stabilize completely. While the inception of TEGs has been examined in several studies, the processes of their stabilization remain poorly documented, especially the cryostructures that form following permafrost aggradation in stabilizing TEGs. For this study, we investigated the impacts of two TEGs in the Canadian High Arctic (Bylot Island, NU, Canada) on ground ice content, cryostratigraphic patterns, and geomorphology to examine permafrost recovery following thermal erosion in ice-wedge polygonal tundra. We sampled 17 permafrost cores from two TEGs – one still active (since 1999) and one stabilized (> 100 years old) – to describe the surface conditions, interpret the cryostratigraphic patterns, and characterize the state of permafrost after TEG stabilization. Although the TEG caused discernable cryostratigraphic patterns in permafrost, ground ice content and thaw front depth in the TEGs were comparable to measurements made in undisturbed conditions. We also noted that, once stabilized, TEGs permanently (at the Anthropocene scale) alter landscape morphology and hydrological connectivity. We concluded that, although the formation of a TEG has profound effects in the short and medium term (years to decades) and leaves near-permanent geomorphological and hydrological scars in periglacial landscapes, in the long term (decades to centuries), High Arctic permafrost can recover and return to geocryological conditions similar to those pre-dating the initial disturbance. This suggests that, in stable environmental conditions undergoing natural variability, permafrost can persist longer than the geomorphological landforms in which it forms.

Improving the ablative properties of silicone rubber by adding aluminum foil/expanded perlite

In this study, aluminum foil (AF) and expanded perlite (EP) were used as the reinforcing fillers to improve the ablation properties of phenyl methyl vinyl silicone rubber composites. The expansion and caramelization of char layer enhanced the ablation and thermal insulation performance of silicone rubber-based composites. The improved bonding of char layer provided a good basis for enhancing ablative properties. The presence of EP increased the emissivity of the char layer which improved the heat radiation properties during ablation process, and it was advantageous to lower surface temperature and reduce thermal erosion. The graphitic degree of char layer was increased which improved high-temperature and oxidative resistance. SEM observations revealed that the surface and cross-section of the char layer were densified, as characterized by the pore size distribution analysis. The above results indicated that the ablation and anti-erosion resistance as well as thermal insulation behavior of silicone rubbers were significantly improved by implementing the expansion and caramelization strategy, which exhibit promising applications as flexible anti-ablation materials for thermal protection purposes.

Comprehensive Insight into the Failure Mechanisms, Modes, and Material Selection of Steam Turbine Blades

Addressing the critical issue of turbine blade failures, particularly in steam turbine systems, this comprehensive review delves into examining and analyzing various failure mechanisms associated with steam turbine blades. The discussion extends to the mode utilized in investigating these failures, with a specific focus on the crucial role of steam turbines in power generation. The review synthesizes various studies that have explored suitable blade materials for optimized performance and reduced failure risks. Findings reveal common failures such as thermal stress, mechanical stress, corrosion, erosion, fatigue, and creep in turbine blades and hubs. Consequently, the review serves as a valuable resource, providing insights into failure mechanisms and advocating for the implementation of suitable materials to enhance the reliability and performance of steam turbine blades.

Comparative study on manufacturing of EDM electrodes by laser sintering process

The abstract aims to investigate the comparative performance of Electrical Discharge Machining (EDM) and Selective Laser Sintering (SLS) with unconventional machining processes. Unconventional machining processes have gained significant attention due to their versatility and capability to fabricate intricate components with high precision. This study focuses on assessing the efficacy of EDM and SLS techniques in terms of data removal rate and relative wear volume. Electrical Discharge Machining (EDM) is a thermal erosion process that utilizes electrical discharges to remove material from a workpiece. In contrast, Selective Laser Sintering (SLS) is an additive manufacturing technique that employs a laser to selectively fuse powdered material, layer by layer, to build up a three-dimensional object. Both methods offer unique advantages in terms of precision, speed, and material compatibility. The performance evaluation of these techniques involves analyzing key parameters such as data removal rate, which measures the volume of material removed per unit time, and relative wear volume, which quantifies the wear on the tool or workpiece during the machining process. By comparing these metrics, insights into the efficiency and effectiveness of EDM and SLS can be gained, aiding manufacturers and researchers in selecting the most suitable method for specific applications. Through experimental investigations and data analysis, this study aims to provide valuable insights into the capabilities and limitations of EDM and SLS in unconventional machining processes. The findings will contribute to advancing the understanding of these techniques and optimizing their utilization in various industrial sectors, including aerospace, automotive, and biomedical engineering. The experimental analysis examines the impact of the Direct Metal Laser Sintering (DMLS) process parameter on sintering depth. The optimized parameters for AlSi10Mg alloy powder sintering were obtained using laser power at 162 W, scanning speed at 156 mm s−1, porosity at 20%, laser area size of 0.2 mm, and layer thickness of 1 mm.

Thermal fatigue behavior of the ZGH451 Ni-based superalloy fabricated by direct energy deposition in the temperature range of 900–1100 °C

In this study, a novel Ni-based superalloy, ZGH451, has been fabricated using direct energy deposition (DED). The thermal fatigue resistance of ZGH451 is systematically evaluated at 900, 1000, and 1100 °C, primarily focusing on the crack initiation and propagation behaviors. The results indicate that higher peak temperatures lead to earlier initiation and more rapid propagation of cracks. Cracks are initiated at the defects and grain boundaries in the vicinity of the notch, and different crack propagation mechanisms (γ' phase slip shearing, γ' phase distortion shearing, and γ' phase rafting shearing at 900, 1000, and 1100 °C, respectively) are the main reason for the different cracks propagation behaviors under the three temperatures. The main crack propagation paths are oriented at approximately 45° with respect to the build direction, suggesting activation of the {111}<110> slip system. Additionally, oxidation reduces the matrix strength and passivates the crack tips, leading to varying rates of crack propagation. At elevated temperatures, the synergistic effects of thermal stress and oxidative erosion are found to be the primary damage mechanisms of thermal fatigue. Overall, the proposed ZGH451 superalloy demonstrates exceptional thermal fatigue resistance, providing a crucial experimental reference for thermal fatigue in additively manufactured superalloys.

State-of-the-Art on Advancements in Carbon-Phenolic and Carbon-Elastomeric Ablatives.

Ablative composites serve as sacrificial materials, protecting underlying materials from high-temperature environments by endothermic reactions. These materials undergo various phenomena, including thermal degradation, pyrolysis, gas generation, char formation, erosion, gas flow, and different modes of heat transfer (such as conduction, convection, and radiation), all stemming from these endothermic reactions. These phenomena synergize to form a protective layer over the underlying materials. Carbon, with its superb mechanical properties and various available forms, is highlighted, alongside phenolics known for good adhesion and fabric ability and elastomers valued for flexibility and resilience. This study focuses on recent advancements in carbon-and-phenolic and carbon-and-elastomeric composites, considering factors such as erosion speed; high-temperature resistance; tensile, bending, and compressive strength; fiber-matrix interaction; and char formation. Various authors' calculations regarding the percentage reduction in linear ablation rate (LAR) and mass ablation rate (MAR) are discussed. These analyses inform potential advancements in the field of carbon/phenolic and carbon/elastomeric ablative composites.

Performance of Atmospheric Plasma-Sprayed Thermal Barrier Coatings on Additively Manufactured Super Alloy Substrates

This work represents a preliminary study of atmospheric plasma-sprayed (APS) Yttria-Stabilized Zirconia (YSZ)-based thermal barrier coatings (TBCs) deposited on forged and additive manufactured (AM) HAYNES®282® (H282) superalloy substrates. The effect of different feedstock morphologies and spray gun designs with radial and axial injection on APS-deposited YSZ layer characteristics such as microstructure, porosity content, roughness, etc., has been investigated. The performance of TBCs in terms of thermal cycling fatigue (TCF) lifetime and erosion behaviour were also comprehensively investigated. In view of the high surface roughness of as-built AM surfaces compared to forged substrates, two different types of NiCoCrAlY bond coats were examined: one involved high-velocity air fuel (HVAF) spraying of a finer powder, and the other involved APS deposition of a coarser feedstock. Despite the process and feedstock differences, the above two routes yielded comparable bond coat surface roughness on both types of substrates. Variation in porosity level in the APS topcoat was observed when deposited using different YSZ feedstock powders employing axial or radial injection. However, the resultant TBCs on AM-derived substrates were observed to possess similar microstructures and functional properties as TBCs deposited on reference (forged) substrates for any given YSZ deposition process and feedstock.

Reduced erosion and its erosion reducing mechanism of gun propellants by octaphenylsilsesquioxane

Low erosion high-energy propellant is one of the research directions to extend the weapon's life and improve the weapon's capability. In this study, energetic propellants containing different corrosion inhibitors were designed and prepared. Close bomb tests and semi-confined bomb experiments were used to investigate the burning and erosion properties of the propellants. The mechanism of erosion-reducing of titanium dioxide (titania, TiO2), talc, and octaphenylsilsesquioxane (OPS) on the propellant was comparatively analyzed. The results show that OPS has the lowest burning rate and the longest burning time, and a minimized loss of fire force, with the best effect of explosion heat reduction. The erosion reduction efficiency of OPS is twice that of TiO2 and talc. The mechanism analysis shows that the decomposition and heat absorption of OPS can effectively reduce the thermal erosion effect and carbon erosion, and the gas produced can reduce the loss of chamber pressure and form a uniformly distributed nano-SiO2 protective layer. This solid-state high-efficiency organosilicon erosion inhibitor is an important guide for designing high-energy low-erosion gun propellants.

Uppermost mantle structure and dynamics of the Tanlu fault zone: New insights from Pn anisotropic tomography

Whether the segmentation of the Tanlu fault zone and mechanism of strong crustal earthquakes are related to the uppermost-mantle structure is still unclear. Here a new high-resolution uppermost-mantle velocity and anisotropy model of the Tanlu fault zone and surrounding areas is determined by using 13,045 Pn arrival-time data. These data are handpicked from seismograms recorded at 120 newly deployed TanluArray portable seismic stations and 337 Chinese provincial seismic stations. The pattern of Pn velocity and anisotropy agrees well with the surface geological and tectonic features. Obvious low-velocity (low-V) anomalies are observed in tectonically active areas, such as the Taihang mountain orogenic belt, the eastern Dabie mountain orogenic belt, and the Sulu fold belt, whereas areas with stable tectonics, such as the North China Basin and the South Yellow Sea Basin, exhibit high-velocity (high-V) anomalies. The fast propagation directions (FPDs) of Pn waves in the study area exhibit a complex distribution, but the FPDs show a rotating feature around the margin of the South Yellow Sea Basin. The block feature of the high-V anomalies beneath the North China Basin and segmentation of the low-V anomalies along the Tanlu fault zone may be related to lithospheric delamination and thermal erosion caused by hot and wet upwelling flows in the big mantle wedge. The 1668 Tancheng earthquake (M8.5) occurred near a low-V anomaly, and recent moderate and strong earthquakes (M > 4.0) took place along the boundaries of the velocity anomalies. These results offer new perspectives on the mantle dynamics and mechanism of strong earthquakes in and around the Tanlu fault zone.

Evaluation of the Thermal Erosion of River Banks Based on Laboratory and Numerical Modeling

Evaluation of the Thermal Erosion of River Banks Based on Laboratory and Numerical Modeling

The first hillslope thermokarst inventory for the permafrost region of the Qilian Mountains

Abstract. Climate warming and anthropogenic disturbances result in permafrost degradation in cold regions, including in the Qilian Mountains. These changes lead to extensive hillslope thermokarst (HT) formation, such as retrogressive thaw slumps, active-layer detachment slides, and thermal erosion gullies. These in turn cause, e.g., degradation of local vegetation, economic losses, infrastructure damages, and threats to human safety. However, despite its importance, there is currently no thermokarst inventory for the Qilian Mountains. Through manual visual interpretation and field validation, we therefore produce the first quantification of HT features. We count a total of 1064 HT features, with 67 % located in the upper reaches of the Heihe River basin, which encompasses ∼ 13 % of the Qilian Mountains region. We further identified that 187 HT features (18 %) existed before 2010, while the remaining 874 (82 %) were initiated in the recent period. More specifically, 392 sites (37 %) were initiated during 2010–2015 and 482 (45 %) after 2015. Thermokarst terrain is observed primarily in areas with shallow active-layer depths (average thickness 2.98 m) on northern shaded slopes of 3–25°, with low solar radiation and moderate elevations ranging from 3200 to 4000 m. This first inventory of HT features is an important and missing piece in documenting changes on the Qinghai–Tibetan Plateau, and this new dataset also provides an important basis for further studies, such as automated extraction of HT features, susceptibility analysis of HT, and estimation of losses caused by HT. The datasets are available from the National Tibetan Plateau/Third Pole Environment Data Center and can be downloaded from https://doi.org/10.11888/Cryos.tpdc.300805 (Peng and Yang, 2023).

Quartz chemical composition and apatite thermochronology trace leucogranite evolution and thermal history in the Koktokay No. 3 rare metal deposit, Chinese Altai

Koktokay No. 3 pegmatite is a globally renowned rare metal deposit. Recently, rare metal-enriched leucogranite was identified within this deposit. The leucogranite is locally cut by No. 3 pegmatite and scattered as fragments among the pegmatite in some outcrops. In this study, we aimed to investigate the emplacement depth, thermal history, and evolution process of leucogranite based on quartz chemical composition and apatite thermochronology. Li, Al, P, Ge are the higher content elements in leucogranite quartz, and Ti is the lower content element (approximately 38.7, 178, 23.9, 2.7, and 2.0 ppm, respectively). The Al, Ti, and Li contents decreased from the core to the rim of the quartz. The leucogranite quartz compositions have a high Ge/Ti ratio, similar to that of the quartz in the Li-Cs-Ta pegmatites, particularly the Koktokay No. 3 pegmatite. This similarity indicates that the leucogranite was formed by a highly evolved melt. Using laser ablation-inductively coupled plasma-mass spectrometry, the U–Pb age of leucogranite apatite was determined as 189.4 ± 6.8 Ma, which is substantially younger than the previous columbite U–Pb age of No. 3 pegmatite, suggesting that the magmatic-thermal activity of No. 3 pegmatite had interfered with the apatite U–Pb closure system. The apatite low-temperature thermochronology results showed that the thermal history of leucogranite can be divided into two cooling stages: rapid cooling stage (180–155 Ma, 9.6–10.6 ℃/m.y.) and slow cooling stage (from 155 Ma to the present day, 0.8–1.0 ℃/m.y.). According to the thermal history, the exhumation and erosion of the Koktokay No. 3 rare-metal deposit is at least 5–6 km long. Leucogranite formation pressure is approximately 2.5 kbar (1.8–3.7 kbar), and the emplacement depth approximately 9.5 km (7–14 km).

Aligned fractures on asteroid Ryugu as an indicator of thermal fracturing

Context. Asteroid and comet surfaces are exposed to a complex environment that includes low gravity, high temperature gradients, and a bombardment of micrometeorites and cosmic rays. Surface material exposed to this environment evolves in a specific way depending on various factors such as the bodies’ size, heliocentric distance, and composition. Fractures in boulders, as seen on asteroid Ryugu, can help to determine and constrain the dominant processes eroding small-body surface materials. It is also possible to estimate fracture growth timescales based on the abundance and length of fractures in boulders. Aims. We analyse the number, orientation, and length of fractures on asteroid Ryugu to establish the relation between the fractures and the processes that may have formed them. We also compare our results to similar investigations conducted on other small bodies and estimate the timescale of fracture growth. Methods. 198 high-resolution Hayabusa2 images of asteroid Ryugu suitable for our fracture analysis were selected and map-projected. Within these images, fractures in boulders were manually mapped using the QGIS software. The fracture coordinates were extracted and the fractures’ orientation and length were computed for 1521 identified fractures. Results. Fractures in boulders on asteroid Ryugu are found to be preferentially north-south aligned, suggesting a formation through thermal erosion. Modeling the fracture length indicates a fracture growth timescale of 30 000 to 40 000 yr, slightly younger than ages found previously for asteroid Bennu. The errors in these ages, due to uncertainties about the thermophysical parameters used in this model, are substantial (−33 000 yr +250 000 yr). However, even with these large errors, the model suggests that thermal fracturing is a geologically fast process. These times are not too dissimilar to those quoted in the literature for Ryugu and Bennu, since similar thermophysical material parameters for Ryugu and Bennu seem likely.

Micro-damage evolution and macro-degradation of red sandstone under thermal and chemical erosion conditions

Micro-damage evolution and macro-degradation of red sandstone under thermal and chemical erosion conditions

Modeling of runoff formation processes with aufeis feed in mountain cryosphere of the north-east of Russia

Aufeis are a key element in the chain of water exchange processes in the permafrost zone. The hydrological role of aufeis in the formation of river flow can be comparable to that of glaciers. Observations of aufeis during the construction of the Baikal-Amur Mainline showed that the share of aufeis runoff in the annual river flow can reach 35% for watersheds with an area of up to 500 km2. Despite the long history of studying aufeis and the results achieved, there are no methods for predicting the development of aufeis processes, as well as hydrological models that take into account the share of aufeis feeding in river runoff. This is due to the lack of observational data on the dynamics and development factors of aufeis. In the last century, long-term studies were carried out on some aufeis in Siberia and the Far East. One of these unique objects is the giant Anmangynda aufeis, which forms in the upper reaches of the Kolyma River basin. The aim of the research is to study the hydrological regime of the Anmangynda river basin and develop a method for accounting of aufeis runoff (module «Aufeis») in the distributed hydrological model «Hydrograph». The module “Aufeis” takes into account two factors of aufeis destruction – under the influence of solar radiation and thermal erosion destruction. The input data is the area of aufeis at the beginning of the warm season and daily meteorological data. The calculation parameters are the coefficients of ice melting and evaporation from ice, as well as the coefficient of the relative area of aufeis depending on the period of destruction, calculated for the modern climatic period. The result of the calculation is the aufeis runoff and the characteristics of aufeis for a given interval. Based on historical data and materials obtained during own field research, the module «Aufeis» was tested. The deviation of the calculated and observed values was 2—10% and 1—9% for the maximum values of the area and volume of the Anmangynda aufeis, respectively. Results of numerical calculations for the period 1967–2022 revealed the dynamics of the contribution of the Anmangynda aufeis to the river flow in different seasons. The expanded functionality of the Hydrograph model has improved the quality of modeling for rivers where aufeis form. For the river basin Anmangynda average Nash-Sutcliffe coefficient and annual runoff error were 0,57 and 13,0% compared to 0,41 and 18,0% when the module «Aufeis» was not used.

Synthesis of magnesium oxide and zinc oxide powders in a glow discharge plasma at atmospheric pressure

Investigation of the processes involved in the synthesis of magnesium oxide and zinc oxide powders using the thermal effects of an atmospheric-pressure glow discharge plasma in an inert gas flow are described. The discharge operates in a repetitively pulsed mode with pulse repetition rate of several tens of kilohertz and pulse duration up to 12 μs, discharge current of 600 mA and voltage up to 300 V. These parameters lead to thermal erosion of magnesium or zinc inserts in a molybdenum crucible. The chemical and phase composition of the erosion products were determined using TEM/EDS and X-ray diffraction analysis, and the composition of the plasma was assessed by optical emission spectrometry. This experimental approach allows fabrication of powders of these metal oxides with characteristic particle size 10–50 nm, and the formation of coatings of these materials in a one-step process.

Lithospheric weakening by a small-scale plume and its geodynamic implications

The process of small-scale mantle plume emplacement within the continental lithosphere influences the dynamic topography and architecture of the lithosphere-asthenosphere boundary (LAB). Furthermore, plume emplacement alters the rheology of the crust and lithospheric mantle through melt-driven, mechanical and thermal weakening. Previous studies of plume emplacement within the lithosphere have described these outcomes, albeit without considering plume-driven weakening. In this study, we quantitatively evaluated the effects of small-scale plume-driven predefined weakening of the continental lithospheric mantle and crust on dynamic topography and LAB depth changes using a series of two-dimensional numerical models. Model calculations showed that small plume-driven predefined weakening led to short-wavelength dynamic topography and LAB depth reduction through both mechanical and thermal erosion of the lithospheric mantle by the plume. An increase in the degree of weakening decreased the lithospheric strength and reduced the LAB depth, thereby transforming the short-wavelength topography from depressions to elevations as the extensional kinematics shifted to compression. Our model findings explain the topography, lithospheric strength, and LAB depth constrained from natural small-scale plume emplacement zones.

A novel structure for improving the service life of a propulsion system by controlling two-phase reactive flow

Methods to control two-phase reactive flow induced by the combustion of propellant particles are important for improving the service life of mechanical systems. A novel groove structure was proposed to control the two-phase reactive flow. A two-phase flow model was utilized to predict propellant combustion in fluid fields and coupled with the transient heat transfer process. The numerical model was validated by comparing numerical and experimental results. Numerical results indicate that the groove structure effectively decreases the scouring velocity of two phases and the accumulation of particles near the barrel surface. The groove also reduces the peak temperature of the barrel surface, which contributes to less thermal erosion. Furthermore, shooting tests prove that the groove structure greatly extends the service life of the barrel. The findings of the study will be applied to improve the service life of propulsion systems.

Deep learning–based inline monitoring approach of mold coating thickness for Al-Si alloy permanent mold casting

AbstractIn the permanent mold casting process, the distribution of mold coating thickness is a significant variable with respect to the coating’s thermal resistance, as it strongly influences the mechanical properties of cast parts and the thermal erosion of expensive molds. However, efficient online coating thickness measurement is challenging due to the high working temperatures of the molds. To address this, we propose an indirect monitoring concept based on the analysis of the as-cast surface corresponding to the coated area. Our previous research proves linear correlations between the as-cast surface roughness parameter known as arithmetical mean height (Sa) and the coating thickness for various coating materials. Based on these correlations, we can derive the coating thickness from the analysis of the corresponding as-cast surface. In this work, we introduce a method to quickly evaluate the as-cast surface roughness by analyzing optical images with a deep-learning model. We tested six different models due to their high accuracies on ImageNet: Vision Transformer (ViT), Multi-Axis Vision Transformer (MaxViT), EfficientNetV2-S/M, MobileNetV3, Densely Connected Convolutional Networks (DenseNet), and Wide Residual Networks (Wide ResNet). The results show that the Wide ResNet50-2 model achieves the lowest mean absolute error (MAE) value of 1.060 µm and the highest R-squared (R2) value of 0.918, and EfficientNetV2-M reaches the highest prediction accuracy of 98.39% on the test set. The absolute error of the surface roughness prediction remains well within an acceptable tolerance of ca. 2 µm for the top three models. The findings presented in this paper hold significant importance for the development of an affordable and efficient online method to evaluate mold coating thickness. In future work, we plan to enrich the sample dataset to further enhance the stability of prediction accuracy.