Melting Erosion Research Articles

Interaction mechanism between DD5 superalloy with different Y content and ceramic molds with Y2O3 layer

DD5 alloys with different Y content were produced by directional solidification (DS) using ceramic molds with the Y2O3 layer. The interaction mechanisms between the corresponding alloys and the Y2O3 layer were discussed. It was found that the Y2O3 layer effectively hindered the direct contact reaction between the active melt and the Al2O3 ceramics, which was conducive to improving the purity of the melt and reducing the loss of Y. Slight dissolution and decomposition of the Y2O3 layer under high temperature melt erosion resulted in the release of Y and O elements into the alloy. The involvement of Y in the melt changed the interfacial reaction mechanism between the Y2O3 layer and the alloy. The interfacial reaction products of melting the DD5 alloy without Y were Al2Y4O9 and Y2O3, while the interfacial reaction product of melting the DD5 alloy with Y was mainly Y2O3.

Ablation of advanced C/C-ZrC-SiC leading edge composites

To mitigate interphase degradation and improve the mechanical and ablation properties of leading edge shaped C/C-ZrC-SiC composites fabricated by reactive melt infiltration, a tailored SiC-C interphase composed of SiC, gas pyrolysis carbon and phenolic resin pyrolysis char was introduced. The SiC-C interphase can effectively protect the carbon fiber from high-temperature melt erosion, improving the flexural strength of the composites by 98%. The mass and thickness change rates of the leading edge composites were 2.96 ± 0.04 µm/s and − 0.42 ± 0.04 mg/s, respectively. The better ablation performance was attributed to the synergistic effect of dense and stabilized Zr-Si-O oxide layer formation and heat transfer.

Study on Mass Erosion and Surface Temperature during High-Speed Penetration of Concrete by Projectile Considering Heat Conduction and Thermal Softening.

The mass erosion of the kinetic energy of projectiles penetrating concrete targets at high speed is an important reason for the reduction in penetration efficiency. The heat generation and heat conduction in the projectile are important parts of the theoretical calculation of mass loss. In this paper, theoretical models are established to calculate the mass erosion and heat conduction of projectile noses, including models of cutting, melting, the heat conduction of flash temperature, and the conversion of plastic work into heat. The friction cutting model is modified considering the heat softening of metal, and a model of non-adiabatic processes for the nose was established based on the heat conduction theory to calculate the surface temperature. The coupling numerical calculation of the erosion and heat conduction of the projectile nose shows that melting erosion is the main factor of mass loss at high-speed penetration, and the mass erosion ratio of melting and cutting is related to the initial velocity. Critical velocity without melting erosion and a constant ratio of melting and cutting erosion exists, and the critical velocities are closely related to the melting temperature. In the process of penetration, the thickness of the heat affected zone (HAZ) gradually increases, and the entire heat conduction zone (EHZ) is about 5~6 times the thickness of the HAZ.

Thermal Stress Analysis of Blast Furnace Hearth with Typical Erosion Based on Thermal Fluid-Solid Coupling

The life of the hearth is the main limiting link of the campaign of a blast furnace. As the equipment for holding molten iron in the furnace, the high-temperature molten iron is in direct contact with the refractory, which makes the refractory have a larger temperature increase. If the temperature gradient inside the refractory is large, it generates large thermal stress and causes the refractory to crack. Blast furnace gas and molten iron intrude into the gap, which directly causes melting erosion and other chemical erosion with carbon bricks. It aggravates the erosion degree of the furnace and seriously affects the production life of the furnace. Therefore, the furnace often occurs with different types of severe depression erosion in the late service of the blast furnace. In this study, the calculation model of the thermal fluid-solid coupling considering the molten iron flow and the solidification of molten iron was established. This calculation model was applied to study thermal stresses in the furnace with severe erosion. Based on the calculation model, the effect of blast furnace production parameters and deadman condition on thermal stresses in the furnace with severe depression erosion were analyzed, including tapping productivity, tapping temperature, cooling intensity, and deadman geometry. The research results are of great significance for prolonging the safe production life of blast furnaces.

Analysis of Melt Erosion and Deposition at Contact Interface in Convex Rail Launcher

In railgun, the melting erosion and deposition at the interface between the armature and rail have severe influences on the bore life and the launch performance. In this article, using a payload-separated method, experiments at a small-caliber rail launcher were performed to study the melting erosion and deposition on the convex rails. The erosion pattern of the armature surface, the mass loss of the armature, and the distribution of the deposition were measured. The results show that central erosion occurs, and edge erosion is significantly mitigated on armatures for convex rails, whereas flat rail presents an obvious edge erosion pattern. Moreover, convex rails reduce material losses of armatures and homogenize depositions. It is found that the initial contact pressure on the contact interface of the convex rail is less concentrated on edges, contributing to the mitigation of edge erosion, which not only allows the molten aluminum to be deposited more evenly but also prevents it from ejecting and damaging the bore insulator.

Numerical Simulation of Melt-Wave Erosion in 2-D Solid Armature

To investigate the erosion phenomenon of solid armature in the sliding electrical contact process, a 2-D numerical model of melt-wave erosion (MWE) based on the finite element method was established in this article. In this model, the magnetic field excitation boundary expands along the erosion direction into a new magnetic field excitation area. And this model was compared with four previous models under the same conditions, and the comparison results show good consistency. In addition, the temperature dependence of conductivity was considered to investigate its effect on MWE. It is found that the erosion velocity is faster and the penetration depth of the magnetic field in the material is greater when the conductivity changes with temperature. Moreover, the peak current density on the armature symmetry line transfers the tail to the lead. For the case of applying pulse current excitation, the melt erosion distance of the armature tends to be gentle with time. And the time ratio and amplitude of input current have a significant influence on the final erosion distance. The results of these investigations will help further understand the onset of the transition.

WATER SOIL EROSION IN RIGHT-BANK UKRAINIAN FOREST-STEPPE ZONE

Problem Statement and Purpose. A water soil erosion is one of the most important ecological problems of the world because in the result of it the soil cover completely destroys and is not able to renew for a long time. In opinion of dr. Montgomery D., the loses of agricultural soils even limited the lifetime of ancient civilizations and the same problem closely touches today human being. Following to the information of scientists in 1970-s, about 430 million ha of lands were destroyed in different countries because of water soil erosion. Annual loses of product lands on our planet equal 5–7 million ha. In Ukraine at the end of first decade of 2000s following to National report (2010) the square of eroded agricultural lands equaled 15.954 million ha or 38.4 per cent of their common territory including 12.940 million ha of arable lands or 39.9 per cent. On average the soil loses about approximately 15 t/ha/year. Thereby the purpose of the study is a spatial distributed quantitative assessment of the intensity of erosion soil loses in the right-bank forest-steppe zone of Ukraine and definition of arable squares with different rates of erosion load considering present climate changes and land use peculiarities. Data &Methods. For the estimation of average soil wash off three typical slope plots (К1-р, К2-р, К3-р) were used. The plots are situated within the territory of Educational and Scientific Stationary of the Odesa I. I. Mechnikov National University that is in Podilsk district of the north part of Odesa region. This territory is on south hills of Podolska upland in forest-steppe zone. The plots are the different parts of small valleys slopes which are annual plowed up and used for growing of the most profit-making crops – wheat, corn, barley and sunflower. No any scientifically based crop rotation uses there at least for the last twenty years. The spatial distributed physical and statistical model of soil wash off and accumulation was used as a working model for the estimation of average annual soil loses consideringthe peculiarities of land cultivation and anti-erosion crops properties. The model was developed in Department of Physical geography, Nature Management and Geoinformation Technology of Odesa I. I. Mechnikov National University and realized in GIS‑package PCRaster (Utrecht University, Netherlands). Results. The quantitative assessment of today erosion soil loses on typical plots considering land use demonstrates very high rate of soil erosion degradation which is obviously representative for the most territories of the right-bank forest-steppe zone of Ukraine. Areas of more than 20 t/ha/year wash off equal 23–27 per cent. Areas of less than 2 t/ha/year wash off where the intensity of soil erosion equals to soil restoration are about one third of all arable lands. The average values of wash off for plots К1-р, К2-р, К3-р are 14.2; 26.3 and 14.8 t/ha/year respectively. However, these values are not above the same ones obtained earlier, but even some less. This is due to the decreasing of soil erosion because of snow melting in the spring which is connected with global warming. But simultaneously the hydrometeorological conditions of rainstorm erosion have not change. And essential decreasing of wash off has not happened because the part of snow melting erosion is only 15–20 per cent in the right-bank forest-steppe zone of Ukraine. The huge values of average wash off and significant areas with high and very high wash off (about one third of arable lands) evidence about decreasing of economic and ecological worth of lands commonly. Applying of soil protection crops rotation well influence on soil decreasing the rate of erosion. The plowing of lands with great slopes (6–7° and more) and using them for row crops without rotation leads to catastrophic wash off and increasing of areas with high erosion danger. Such lands need to be exclude of plowing up.

Effect of surface structure unit of 3D needled carbon fiber preform on the ablation improvement of “Z-pins like” V0.9-Si0.1 rod for C/C–ZrC–SiC

The effects of the different surface structure units due to “Z-pins like” V0.9-Si0.1 rods on the improvement of the ablation resistance of C/C–ZrC–SiC were investigated. The ablation properties of the V0.9-Si0.1 rods acting on the surface of short-cut fibre web and laminated layers were tested for different ablation times. The results showed that although the ablation resistances of the composites with different surface structure units improved using neoteric “Z-pins like” V0.9-Si0.1 rods as polybasic multiphase oxide compensators, the improvement mechanisms were different. For an ablation time less than 180 s, the rods perpendicular to the short-cut fibre web resulted in a higher improvement in ablation resistance by a liquid/gas multicomponent oxide compensation mechanism. Whereas, for an ablation time over 180 s, the rods perpendicular to the laminated layers resulted in a higher improvement because of the oxide melting erosion experienced by the short-cut fibre web surface.

Hydrological characteristics of snow melt erosion areas in the Krasnoyarsk forest-steppe

Hydrological factors determine the features of relief formation in all territories where surface runoff is formed. They determine the degree of ruggedness and the nature of the relief. Changing from year to year, they interact with the underlying surface, activating the processes of erosion and planar flush of the fertile topsoil on it. The need to model and determine their intensity in different periods is due to the annual use of these territories for agricultural needs, during their plowing and sowing. The article analyses the main characteristics of surface runoff on the territory of the Krasnoyarsk forest-steppe. The result of hydrological and geomorphological analysis of the catchment area in the key study area is presented. The main indicators of autumn soil moisture are characterized and their effect on the washout of the solid fraction within the key site Dolgiy Log is estimated.

Influence of Caliber Height on Armature Current Melt Erosion in Rail Gun

Keeping good electrical contact at the armature/rail interface and the structural integrity of the armature during electromagnetic launching is critical to its performance. In this article, the influence of armature height on the erosion of armature’s tail is studied through experiments. The results of the armature current melt erosion (CME) of different linear current densities are summarized. For armatures with lower height, the CME tends to develop vertically, which is not conducive to keeping the structural integrity of the armature. For armature with higher height, the CME develops from the middle position of the armatures’ tails to both horizontal and vertical directions. In this article, the finite element software COMSOL is used to analyze the initial contact position of the armature/rail and the current density distribution of the armature/rail interface. The reasons for the starting position of armature CME and the differences in the morphology of armature CME in three different heights are explained. Finally, from the theoretical point of view, the influencing factors of armature CME are analyzed.

Erosion behaviour of cobalt-based coatings with different carbide contents under high-speed propellant airflow

ABSTRACT Three different cobalt-based alloy coatings were prepared on the surface of PCrNi3MoVA steel by plasma transferred arc method by adjusting the contents of Cr, W, and C. An accelerated erosion test was performed on the coatings under high-pressure hot airflow environment generated by propellant combustion in gun bore. Scanning electron microscopy and X-ray diffractometry were used to analyse the microstructure of the three coatings before and after erosion. The thermal behaviour of the three coatings was analysed by differential scanning calorimetry. Results show that erosion mainly occurs between the dendrites on the surface of the coating, manifested by eutectic melting erosion and carbide cracking. As the contents of Cr, W, and C decrease, the amount of carbides formed in the coating decreases, the erosion behaviour of the coating is significantly weakened, and the erosion resistance is highly improved.

Research Progress of Magnesium Stabilized Aluminum Titanate and New Application of It in Pigment

Aluminum titanate has been widely used in low expansion applications and its thermal stability has been a hot topic. The stability of aluminium titanate research for improving product quality, and expanding its application field is of great significance. Aluminum titanate as glass melt erosion resistance and high temperature resistant, can be applied to high temperature pigment base. The medium temperature stability of aluminum titanate can be improved by ion doping, and magnesium stability of aluminum titanate has been widely studied. Therefore aluminium titanate is expected to become an ideal high temperature ceramic base material. In this paper, the preparation technology of magnesium-stabilized aluminum titanate powder was reviewed, and the preparation of magnesium-stabilized aluminum titanate powder by non-hydrolyzed sol-gel was mainly introduced.

The Effect of Current and Speed on Melt Erosion at Rail-Armature Contact in Railgun

In this paper, launch experiments are performed to investigate the effect of current and speed on current melt erosion with a 20-mm caliber lab-scale railgun. Armatures are kept in bore by using payload separated method to keep recovered armatures intact. Launch experiments with different current magnitudes are conducted, while speed is limited within 150 m/s by heavy payloads. Launch experiments are conducted at different speeds at the same current magnitude. The desired speed was achieved by adjusting the mass of payload for each test. Erosion results with increasing current and speed are summarized. Location of peak erosion depth and erosion amounts under the effect of current and speed are analyzed based on current simulation and profile measurement. The current melt erosion starts at the side edge near the midpoint of the armature in the longitudinal axis direction. Then, this erosion spreads longitudinally forward to the leading edge along the sides and transversely to midline of armature surface under the influence of current but moves toward to trailing edge under the influence of speed. Higher current and speed will facilitate the corresponding erosion propagation. The location of the peak erosion depth appears to be stable in space for the increasing current magnitude, which is consistent with stationary current simulation at upslope current stage, but gradually moves toward to the trailing edge as speed increases. This may because location of peak current density moves toward to the trailing edge due to the velocity skin effect. Measurement results of mass loss indicate that the amount of material eroded increases substantially with current, and less so with speed. Furthermore, the propagation trend of current melt erosion is discussed.

Analysis of the Melt Erosion Patterns at Rail-Armature Contact of Rail Launcher in Current Range of 10–20 kA/mm

Sliding electrical contact between rail and armature in rail launchers is characterized by high speed and large current. Melt erosion is caused by the current concentration on the contact surface of armature. This current melt erosion (CME) has been experimentally studied in the current range of 10–20 kA/mm with a 20-mm caliber lab-scale rail launcher, and payload separated method was used to keep the recovered armatures intact. Thus, the onset behavior and erosion patterns of CME can be successfully observed in such relatively low current densities. In this paper, we will further our study to analyze the patterns of CME with the increasing current densities under the effect of different initial mechanical contact force. Results show that CME all start at the side edge, and then spreading longitudinally and transversely with the increase of current. It is found that the starting position of CME appears near the trailing edge at small mechanical contact force and moves to the leading edge with larger mechanical contact force. At the same current magnitude, erosion amounts are much more under small mechanical contact force. Stationary mechanical contact pressures and current distribution of armature surface are simulated to investigate the effect of initial mechanical contact force on starting position of CME. Current distributes at the edges of actual contact zone and the maximum of current density appears at the side edges of armature. As the initial mechanical contact force increases, actual contact zone and current density move toward to the leading edge from trailing edge. It can be confirmed that the erosion starting position is at the side edge along actual contact zone and will move toward to the leading edge from trailing edge with the increase of initial mechanical contact force. Smaller initial mechanical contact force will cause more erosion at the same current magnitude because of larger current density. Furthermore, an average friction coefficient calculation method is proposed to evaluate the melt lubrication effect of CME. The result shows that the lubrication effect becomes better with larger current densities.

Effects of pyrocarbon matrix type on the microstructure and properties of C/ZrC composites

Three porous C/C preforms with various carbon matrix type (deposited PyC, vitreous carbon and pitch derived carbon), and reinforced by three-dimensional needled felt, were used to prepare C/ZrC composites via reactive melt infiltration of zirconium. C/ZrC composites prepared from pitch derived C/C preform obtained the highest density of 3.31 g/cm3 and lowest porosity of 9.8%. The deposited carbon matrix can protect the carbon fiber from melt erosion at high temperatures, leading to the higher flexural strength and modulus of 203 MPa and 15.5 GPa. But the C/ZrC fabricated by the phenolic resin derived C/C exhibited the poorest mechanical properties because of the weak interface bonding strength and carbon fiber degradation. And the composites exhibited the poorest anti-ablation properties because the amorphous vitreous carbon was easier to be oxidized and eroded than the others. But pitch derived composites displayed the best anti-ablation properties, with linear recession rate of 0.0053 mm/s and mass loss rate of 0.0035 g/s, close to those of deposited carbon derived composites.

Research on Melting Erosion Law of a Multiturn Series–Parallel Railgun During Launching Period

The melting erosion law of the contact interface between armature and rails on the electromagnetic (EM) railgun is one of the key factors affecting the launching performance. In order to study the melting erosion law on the contact interface of a multiturn series-parallel (MSP) railgun, an EM structure thermal multiphysical field coupling model is built, and the armature velocity, contact force, and temperature of contact interface under different current peak values and shrink ranges are analyzed. Besides, the related verification experiments are carried out, and the melting erosion law of the contact interface is obtained. The results of simulations and experiments show the following conclusions: First, during the launching, the contact force between armature and rails varies with current fluctuation. Second, the friction heat power varies directly with the contact force, but Joule thermal power caused by contact resistance varies inversely with the contact force. Third, the ambient temperature of the sliding contact interface can be further improved by reasonable design of armature shrink range. Fourth, due to the inevitable wear during sliding, the melting area of the armature contact surface gradually transfers from the initial contact area to the tail. The above-mentioned conclusions can provide a technical reference for the high-speed experimental study of MSP railgun.

Experimental Studies on Melt Erosion at Rail-Armature Contact of Rail Launcher in Current Range of 10–20 kA/mm

Sliding electrical contact between rail and armature in rail launchers is characterized by high speed and large current. Melt erosion is caused by the current concentration on the contact surface of armature. Because the current melt erosion (CME) was considered to be a main mechanism of armature-rail contact failure, it was experimentally and theoretically studied in the early years using current density of 30–40 kA/mm, which is the exact driving current of rail launches. However, the critical behavior at the onset of CME cannot be observed due to the serious melt erosion at such high current densities. In this paper, the CME of armatures has been experimentally studied in the current range of 10–20 kA/mm with a lab-scale rail launcher. A payload separated method was used to keep the recovered armatures intact. The critical process for the onset of melting was observed and the erosion spreading patterns on the contact surface was analyzed. It is found that the current melt-wave model postulated in early years cannot describe the development of CME in our experiments. The result shows that current erosion mostly occurs at the static and the low-velocity stage of armature. The CME begins at the point of maximum contact pressure provided by armature-rail interference fit, and then, the melt erosion spreads longitudinally and transversely. The current erosion is affected by both current distribution and the movement of liquid aluminum. In longitudinal direction, the flow of liquid aluminum results in erosion propagation to leading edges. The transverse width of erosion zone expands with increasing current magnitude along the edge of interference fit.

Two-dimensional numerical study of ELMs-induced erosion of tungsten divertor target tiles with different edge shapes

Thermal performance of the divertor tile with different edge shapes was assessed numerically along the poloidal direction by a two-dimensional heat conduction model with considering the geometrical effects of castellated divertor tiles on the properties of its adjacent plasma. The energy flux density distribution arriving at the castellated divertor tile surface was evaluated by a two-dimension-in-space and three-dimension-in-velocity particle-in-cell plus Monte Carlo Collisions code and then the obtained energy flux distribution was used as input for the heat conduction model. The simulation results showed that the divertor tiles with any edge shape of interest (rectangular edge, slanted edge, and rounded edge) would melt, especially, in the edge surface region of facing plasma poloidally under typical heat flux density of a transient event of type-I ELMs for ITER, deposition energy of 1MJ/m2 in a duration of 600μs. In comparison with uniform energy deposition, the vaporizing erosion was reduced greatly but the melting erosion was aggravated noticeably in the edge area of plasma facing diveror tile. Of three studied edge shapes, the simulation results indicated that the divertor plate with rounded edge was the most resistant to the thermal erosion.

A laboratory model for melting erosion of a magma chamber roof and the generation of a rhythmic layering

A hot magma chamber can ascend by melting the roof rock, a process which in turn affects the magma composition. The disaggregated mineral particles which consisted the roof rock will descend in the magma chamber to form a sedimentary cumulate. However, the fluid dynamics leading to the formation of the sediment, and how we can decipher them is unknown. Here we conducted a series of experiments modeling melting erosion of the roof with particle size consisting the roof rock as the parameter. We find that there is a critical particle size below which the melting erosion occurs rhythmically. Melting erosion stops because the disaggregated particles are suspended in the magma chamber and suppress the vertical heat transfer. The suspension then separates into an upper clear layer and a lower suspension layer. Eventually, the heated stratified layers become unstable. An overturn occurs, and melting erosion resumes. When the particles consist of two sizes such that at least one of them is smaller than the critical size, a rhythmic erosion occurs. Particles are sorted during each erosion period, and a size‐graded rhythmic layering is spontaneously generated. We estimate that rhythmic layering can be generated from melting erosion in a basaltic magma chamber when the grain size of the roof rock is ≤ 0.6 mm, assuming a vertical temperature difference of 10°C. We suggest that rhythmic roof melting coupled with particle settling is one possible mechanism for generating the rhythmic layering which is commonly observed in solidified magma chambers.

Probabilistic approach to the calculation of soil erosion loss

An algorithm was proposed for the simulation of water erosion as a stochastic process. Two concepts were used: the random single event (e.g., rainfall) and the implementation of a random process as a series of random single events during a long time period. The Monte Carlo method and previously developed and substantiated equations for rain and snow melt erosion were used for the numerical simulation of random single events. The simulation resulted in a series of values for the soil loss during the specified time period, from which the probability distribution of the soil loss during this period could be assessed. The testing results for the chernozemic soils of the Central Chernozemic region showed that the error of the soil loss calculation was 13% during 200 years of land use. It was shown that the SCS equation developed for the United States’ conditions can be used to calculate the rainfall runoff in the Central Chernozemic region of Russia. Problems that cannot be solved using deterministic models and the available observation data can be solved on the basis of the obtained probability distributions.