Abrasive Environment Research Articles

The Particle Breakage Effect on Abrasive Wear Process of Rubber/Steel Seal Pairs under High/Low Pressure.

Pressure has a significant effect on rubber seal performance in the abrasive environments of drilling. The micro-clastic rocks intruding into the seal interface are prone to fracture, which will change the wear process and mechanism, but this process is not yet known at present. To explore this issue, abrasive wear tests were carried out to compare the failure characteristics of the particles and the variation wear process under high/low pressures. The results show that non-round particles are prone to fracture under different pressures, resulting in different damage patterns and wear loss on the rubber surface. A single particle force model was established at the soft rubber-hard metal interface. Three typical breakage types of particles were analyzed, including ground, partially fractured, and crushed. At high load, more particles were crushed, while at low load, shear failure was more likely to occur at the edges of particles. These different particle fracture characteristics not only change the particle size, but also the state of motion and thus the subsequent friction and wear processes. Therefore, the tribological behavior and wear mechanism of abrasive wear are different at high pressure and low pressure. Higher pressure reduces the invasion of the abrasive particles, but also intensifies the tearing and wear of the rubber. However, no significant differences in damage were found for steel counterpart throughout the wear process under high/low load tests. These results are critical to understanding the abrasive wear of rubber seals in drilling engineering.

Effect of carbide orientation during single scratch test in directionally solidified and heat-treated high chromium cast irons

In this work, a billet of eutectic high chromium cast iron, material commonly used in highly abrasive environments, such as in grinding and milling, was unidirectionally solidified. The resulting microstructure was composed of oriented M7C3 carbides and eutectic matrix. Specimens were cut parallel and transversally to the billet axis and split into two groups. Both were heat treated with different austenitization temperatures. The temperature for the first group was 1100 °C, and the value for the second was 950 °C, providing matrix instrumented indentation hardness values of 8.0 and 6.3 GPa, respectively. This procedure resulted in specimens with three carbide directions dispersed in two different matrices. Samples were evaluated by means of single scratch test with a cono-spherical diamond stylus under progressive and constant normal load conditions. To support the analysis, a non-contact 3D surface profiler and scanning electron microscopy (SEM) were used to characterize the scratched surfaces. Progressive load tests indicated a transition in wear micro-mechanisms which was mainly observed in the samples with the long axes of the carbides parallel to the wear surface and oriented orthogonal to the scratch direction and with matrix hardness of 6.3 GPa. On the other hand, constant load tests showed that carbides with the long axes parallel to the wear surface and oriented parallel to the scratch direction tend to produce deeper scratchers with higher ridges than in the other directions. Results also indicate that the hardness, despite being an important variable, does not entirely explain the behavior of the material under single scratch, since the orientation of the carbides with respect to the scratch direction must also be considered.

INCREASING THE RESOURCE OF VEHICLE PARTS BY COMPOSITE MATERIALS DURING THEIR RESTORATION REPAIR

To restore machine parts used quite a large range of materials in the form of wire, powders, flexible cords, etc. However, it is not always possible to provide the required resource for the restoration of parts working in abrasive and corrosive environments. One of the modern directions of increasing the wear resistance and other properties of reducing coatings is the use of composite materials. This paper presents the results of research on the development of a composite modifying material to control the properties of reducing coatings based on commercially available powder material PG- 10N-01. It is shown that the developed composite material obtained using the SHS process from a powder mixture of Ti+C+SiO2+Al2O3+Fe2O3+Al+PT-NA-01 provides a higher (1.65 times) abrasive resistance of the deposited alloy coating PG-10N-01 when modifying its composite material in the amount of 20%.

Alloy design for microstructural-tailored boron-modified ferritic stainless steel to ensure corrosion and wear resistance

Ferritic stainless steels armored with borides had their endurance tested in demanding both abrasive and corrosive environment. The degradation was investigated through a very aggressive plate-on-cylinder wear test in water-based drilling mud containing chlorides, which was designed to simulate, in laboratorial scale, the corrosive tribosystem found in the wear of risers and casings used in deep water oil exploitation. A commercially-grade 430 ferritic stainless steel containing boron content far beyond its solubility limity, namely 1.2 and 3.5 wt.%, was processed by spray-forming to induce a ferritic stainless steel matrix protected by a boride skeleton. Additional corrosion assessment was performed by potentiodynamic polarization and electrochemical impedance spectroscopy in 0.27 M KCl solution, since KCl is a common clay swelling inhibitor. For comparison, API 5L X80 steel was also included since this material is used in risers and casings manufacture. The addition of boron (1.2 and 3.5 wt.%) led to the formation of microstructures composed of an α-ferrite matrix with homogeneously distributed M2B-type borides of different morphologies. Electrochemical tests revealed high corrosion resistance of the alloy with 1.2 wt.% B. However, the alloy with 3.5 wt.% B showed a considerable decrease in corrosion resistance due to Cr-depletion of the ferritic matrix given the M2B formation richer in Cr. Therefore, the alloy with 1.2 wt.% B offered the best tribocorrosion resistance.

A new approach to improve some properties of wire arc additively manufactured stainless steel components: Simultaneous homogenization and boriding

Arc-directed energy deposition (Arc-DED), also commonly referred to as wire arc additive manufacturing (WAAM), is a cost-effective 3D metal additive manufacturing process in which large metallic parts can be produced due to high deposition rates. Stainless steels, widely used in many areas due to their excellent corrosion resistance, are one of the most produced materials by the WAAM method. However, stainless steels have low surface hardness. Moreover, the high heat input in the deposition process in WAAM sometimes causes the mechanical properties of stainless steels to be lower than casting or wrought stainless steels. These considerations limit the use of WAAM stainless steels, especially in abrasive environments. For this purpose, 307ER stainless steel produced by WAAM method was subjected to homogenization and boriding process simultaneously at 1000 °C for 1 h and the effect of applied heat treatment on microstructure, phase components, hardness and wear resistance was investigated. The results showed that with the boriding process, a 30 μm thick boride layer consisting of FeB, Fe2B, Cr5B3 and MnB phases with a hardness of 21.5 GPa and a modulus of elasticity of 310 GPa was formed in addition to the dissolution of interdendritic regions in the as-built structure and a complete homogenization of the microstructure. Furthermore, owing to the high hardness and elasticity modulus in addition to the boride layer's self-lubrication properties obtained on the WAAM samples surfaces, 31.84 times and 8.06 times increased in wear resistance at room temperature and 500 °C temperature, respectively, and a decrease in friction coefficients was obtained. Moreover, the results showed that the simultaneous homogenization and boriding processes of stainless steels produced by the WAAM method would improve their microstructure and tribological behavior. This way, these steels can be used in wider areas of application.

Increasing the Durability of Tools for Forest Road Maintenance

To ensure the care of forests, it is necessary to make them sufficiently accessible by forest roads. The basic working tool are hammers, or round shanks of various shapes, composed of a body and a tip. They are subject to a strong abrasive environment, which often leads to damage up to the complete destruction of the functional part of the tool. For these reasons, it is necessary to deal with the possibilities for increasing their lifetime. One of the possibilities of increasing the service life of these tools is hardfacing by welding. The article deals with the abrasive resistance of the original material of the tool and the hardfacing materials. Based on the chemical analysis of the base material of the tool, we found that the tool is made of manganese steel 38Mn6. This material was used as a standard and was compared with the hardfacing materials Abradur 58, E DUR 600, UTP DUR 600 and OK 84.58. Electron microscopy was used to evaluate the microstructure. Next, the Rockwell hardness measurement was performed on the samples. The original tool material 38Mn6 reached the lowest hardness value, namely, 21 HRC. The highest value was reached by the hardfacing material E DUR 600, namely, 59 HRC. Subsequently, a test of resistance to abrasive wear was performed according to GOST 23.208-79. Based on this test, we can conclude that the highest value of resistance to abrasive wear was achieved by Abradur 58. Even though the hardness of this coating was slightly lower than the hardfacing material E DUR 600, specifically 56 HRC, we can state that this hardfacing material (Abradur 58) achieved the best results among the investigated materials.

Corrosion Wear of Hypereutectic High Chromium Cast Iron: A Review

Hypereutectic High Chromium Cast Iron (HHCCI) is a new type of corrosion-wear-resistant material developed from ordinary high chromium cast iron by increasing the chromium and carbon content and is often used in abrasive environments where wear and corrosion interact. The corrosion wear resistance of the HHCCI is related to the number, size, shape and distribution of carbides and the microstructure of the matrix. This paper reviews the research progress in improving the corrosion wear resistance of HHCCI from various aspects such as primary carbide refinement, heat treatment, deep cooling treatment and alloying, etc. Among the methods of refining primary carbides are modification, semi-solid treatment and current pulse treatment. In addition, we also analyze the potential of Cr, V, Nb, Mo, Mn, W, Ni, Cu, Si, N and other alloying elements to improve the corrosion wear resistance of HHCCI. The mechanism for improving the corrosion wear resistance of HHCCI is also explored in depth and research contents worthy of attention are proposed to further improve the corrosion wear resistance of HHCCI. In the future, the author believes that modification + alloying + heat treatment is the most potential application method to improve the corrosion wear resistance of HHCCI. The corrosion wear resistance of HHCCI can be further improved by refining the primary carbide (such as adding rare earth, Ti and other modified elements) + heat treatment (with cryogenic treatment) to improve the strength + alloying (such as adding low-cost, high-potential alloy elements such as N and Si) to improve the corrosion wear resistance of the matrix.

Improved Wear and Corrosion Resistance in TiC-Reinforced SUS304 Stainless Steel

Herein, the vacuum arc-melting process is applied to incorporate various amounts of Ti and C into SUS304 austenitic stainless steel based on the high-entropy alloy concept to obtain wear- and corrosion-resistant alloys with in situ carbide reinforcements. Five compositions containing the equivalent of 5, 10, 15, 20, and 25 volume percentages of TiC in SUS304 stainless steel, named A1, A2, A3, A4, and A5, respectively, were designed, melted, and solidified by the arc-melting method. Microstructural analyses, hardness measurements, immersion tests in four corrosive solutions, electrochemical measurements in a 3.5 wt % NaCl(aq) solution, and tribological tests were conducted to determine the properties and explain the relevant mechanisms. A1 exhibited a eutectic structure between FCC dendrites, while A2, A3, A4, and A5 possessed proeutectic dendritic TiC, FCC dendrites enveloping the TiC dendrites, and a eutectic structure. A5 represents the optimal composition. Its hardness, wear resistance, and corrosion resistance are 2, 14, and 4 times higher than those of SUS304, respectively. Additionally, its wear resistance is 2.5 times that of high-chromium cast iron. Consequently, A5 could have a 2.5-fold longer lifetime in wear operation. Therefore, A5 could be potentially applied in corrosive and abrasive environments, such as rotary shafts, rotors, bearings, and structural parts in food, chemical, and optoelectronic industries.

INFLUENCE OF THE CHEMICAL COMPOSITION OF HIGH-CHROMIUM CAST IRON ON THE CONTENT OF CHROMIUM IN NEAR-CARBIDE ZONES AFTER ANNEALING AT 720 °С

Purpose. Increasing the corrosion resistance of wear-resistant high-chromium materials operating in a liquid abrasive environment makes it possible to increase the service life of products made from these materials, which is an important task in materials science. One of the main reasons for the occurrence of damage during corrosion processes is the uneven distribution of chromium in the metal base, which leads to the formation of microgalvanic pairs on the surfaces of parts in an electrolytic environment. The creation alloys of wear-resistant high-chromium, in the metal base of which microgalvanic vapors are not formed, is a promising direction for increasing the corrosion resistance of such materials. Investigation of chromium distribution processes after heat treatment parts of high-chromium cast iron, namely the formation of metal base zones near carbides.
 Research methods. Analytical review of publications. Metallographic, microstructural and local X-ray microanalysis. Mathematical modeling of processes.
 Results. It was revealed that during the heat treatment in high-chromium cast irons, structures with significant segregation of chromium are formed. It has been established that after annealing of castings at 720 °C, the minimum chromium content in the metal base is observed in the zones near carbides, and the maximum in the central zones of the graids. The presence zones with a chromium content of more than 12 % (positive potential) and less than 12 % (negative potential) leads to the formation of microgalvanic couples, which is the main reason for the acceleration of corrosion damage in the metal base. The dependence of the chromium content in the zones near the carbides after annealing at 720 °C on the chemical composition of cast iron has been determined.
 Scientific novelty. The mathematical model is proposed for determining the chromium content in the zones near carbides after annealing at 720 °C with an exposure of 9 hours from the chemical composition of cast iron in the Fe-C-Cr-Mn-Ni system. This makes it possible to predict the chromium content in the zones near the carbides and prevent the formation of microgalvanic pairs.
 Practical value. The dependence (mathematical model) obtained can be used in the development of compositions of high-chromium wear-resistant cast irons with increased corrosion resistance and machinability.

INCREASING THE RESOURCE OF WORKING PARTS OF MACHINES OPERATED IN AN ABRASIVE ENVIRONMENT BY THE METHOD OF CARBOVIBROARC HARDENING

The problem of increasing the resource of working parts of machines operated in an abrasive environment is still relevant. A promising way to strengthen the working parts operated under these conditions is carbovibroarc hardening. Currently, the issues of using iron-based matrix powders as part of multicomponent pastes for carbovibroarc hardening remain insufficiently considered, although they have a number of advantages over other powders. (Research purpose) The research purpose is substantiating the expediency of using an iron-based matrix powder as part of a multicomponent paste for carbovibroarc hardening in order to increase the life of the working parts of machines operated in an abrasive environment. (Materials and methods) Powders PR-KH30SRNDYU on an iron basis and PR-NH17SR4 on a nickel basis were used in the research as matrix material of multicomponent pastes, boron carbides B4C and silicon SiC were used as ceramic components of pastes. carbovibroarc hardening was carried out using the VDGU-2 installation in the following modes: current strength - 70 amperes, vibration frequency of the carbon electrode - 25 hertz. (Results and discussion) It has been shown as a result of scientific research that metal-ceramic coatings obtained on pastes containing matrix powder PR-X30SRNDU 65 percent by weight, boron carbide as a ceramic component 25 percent by weight and cryolite - the rest have the highest microhardness. The microstructure of the obtained coatings is dense and practically nonporous, and their wear is 2.7 times less than the wear of steel 65G, adopted as the reference standard. (Conclusions) The data obtained confirm the feasibility of using iron-based matrix powders as part of multicomponent pastes for carbovibroarc hardening. Their use will significantly increase the resource of working parts of machines operated in an abrasive environment.

Износостойкость низколегированных сталей в абразивной среде

The import substitution of agricultural machinery implements is possible with the development of high quality steel and hardening technologies appropriate to the operating conditions of agricultural machinery. Along with high wear resistance in abrasive environment, steel must have high ductility and impact toughness. To investigate wear resistance of the developed low-alloy steels in the abrasive environment and estimate the possibility of their application for manufacturing high-resistance working tools of agricultural machinery the authors developed four batches of steel samples with additives. All samples were subject to heat treatment with heating to 900°C and quenching in water at 20°C. The second group of samples was additionally tempered at a temperature of 280°C for an hour, followed by air cooling. The wear resistance of samples was determined according to GOST 23.208‑79 with the test equipment. The least wear intensity of 0.0581 g/m was recorded for steel 0.43C‑1.60Si‑0.01Mn‑1.1Cr‑0.95Mo‑0.08V‑ 0.05Nb‑0.04Ti subjected to heat treatment with quenching. The high tensile strength of 2170 MPa was obtained through the formation of carbonitrides enriched with Nb. The wear resistance of this steel grade is 1.66 times higher than that of the 65G steel grade. The heat treatment of quenching with tempering yielded the relative wear resistance of the given steel by 10.7% lower, which can be explained by phase transformations reducing the ultimate strength to 2040 MPa, but increasing the plasticity of steel. Studies have shown a wide range of changes in wear resistance depending on the heat treatment mode. This makes it possible to modify the structure of steel in relatively small temperature intervals of quenching and tempering, thereby influencing the properties that provide the greatest wear resistance.

EVALUATION OF NOMENCLATURE OF MACHINE PARTS, THAT DETERMINE RESOURCE

The development of machine designs occurs with a constant desire to increase their productivity, which is almost always accompanied by an increase in the mechanical and thermal tension of the movable joints of parts. At the same time, the tasks of achieving high reliability and durability of the machine, reducing its weight, reducing the consumption of scarce materials are set. Based on a comprehensive assessment of automotive parts that determine the resource, it was found that abrasive wear prevails over all other types of wear. About 83% of automotive parts have wear up to 0.6 mm. When interacting with the soil, the working bodies of tillage and planting machines are subjected to intense abrasive wear. In addition, the working bodies of agricultural machines are operated in a chemically abrasive environment, which is associated with the addition of various fertilizers to the soil and the presence of moisture in it. Together, these factors have such a strong influence on the working bodies of agricultural machines, which makes them unusable after almost several hours of intensive work. Currently, in Ukraine, the following working bodies of tillage machines are used for tillage in agriculture: ploughshares, pointed and one-sided cultivator paws, various coulter designs, harrow discs, husker discs, baking powder, etc. In the soil environment, the working bodies are subject to intense abrasive wear. Typical representatives of the working bodies of tillage machines with cutting elements are the paws of cultivators designed for loosening, destroying weeds and mixing soil particles. The analysis of methods and methods of restoration of machine parts used at the enterprises of the agro-industrial complex showed that more than 60% of the parts are restored by surfacing and gas thermal spraying. Keywords: resource, repair, restoration, surfacing, thermal spraying, wear, durability

Study on agitator resistance to hydroabrasive wear

Resistance of structural materials used in the mining industry to hydroabrasive wear is one of the key factors for the durability of many mechanisms, especially agitators. When mixing concentrated slurries, rotating agitator elements interact with suspended abrasive particles of the rock. Inadequate selection of structural materials for these elements causes frequent replacements due to hydroabrasive wear and related process shutdowns. Hydroabrasive wear by solid particles occurs as a result of cyclic impacts of fine solid particles entrained in a gas or liquid flow and striking the surface of a solid body. The mechanical action of these particles is similar to abrasion and includes plastic deformation and brittle fracture. In addition to hydroabrasive wear, exposure to chemicals leads to corrosive wear. Material resistance to corrosion depends on many factors related to both the material and the corrosive solution. This paper presents the results of a study of resistance of various materials to hydroabrasive wear in a corrosive and abrasive environment. Samples made in the form of 3–4 mm thick rectangular plates were selected for the study. St3sp and 12Kh18N10T grade steels were used, as well as a composite material consisting of glass fiber and polymer binders. The test results show that resistance of the composite material is much superior to that of metal samples. This is mainly due to the inertness of polymeric materials to corrosion.

Analysis of Wear Properties of Powder Metallurgy Steel in Abrasive Soil Mass.

This study presents the results of testing for abrasive wear of Vanadis 60 SuperClean powder metallurgy steel as compared to Hardox 600 steel and PMFe60P padding weld. The testing was conducted by the “rotating bowl” method using natural abrasive soil masses. Two types of abrasive masses with particle size distributions corresponding to light soil and medium soil were used. The obtained results enable the conclusion that the weight loss for Vanadis 60 SuperClean powder steel in both types of abrasive mass was approximately seven times lower than that for Hardox 600 steel and two times lower than PMFe60P padding weld. The high resistance of powder steel to abrasive wear in abrasive soil masses is related to the presence of a large number of fine M6C (tungsten-molybdenum) and MC (vanadium) carbide precipitates in its microstructure. The obtained test results indicate that the application of Vanadis 60 SuperClean steel may be extended to working elements operating in mineral abrasive environments.

Wear Intensity of an Epoxy Compound in a Loose Abrasive Environment under Negligible Shock Actions

Wear Intensity of an Epoxy Compound in a Loose Abrasive Environment under Negligible Shock Actions

Influence of rotation speed on abrasive wear behavior of the UHMWPE in lubrication environment

AbstractTo better understand the damage failure mechanism of ultra‐high molecular weight polyethylene (UHMWPE) in engineering application environments, a study was conducted to explore the effect of rotation speed on its abrasive wear performance in lubricant media containing abrasive particles, especially in comparison to the water. The wear mechanism was analyzed by friction coefficient and wear behavior. The results show that UHMWPE has excellent tribological properties in the water and is seriously worn in the abrasive environment. Under the condition of abrasive wear, there exists a critical rotation speed (360 r/min) leading to a shift in the wear mechanism of UHMWPE and obtaining the lowest wear rate of about 8.49 × 10−6 mm3/N•m. At below critical rotation speed, three‐body abrasive wear and adhesive wear mainly occur in UHMWPE; And at above critical rotation speed, the wear mechanism is mainly the plowing effect of particles on the material, and the furrow width can reach 40 μm. It is believed that this study can help to improve the understanding of the wear mechanism of UHMWPE, which can support the enhancement modification of the material and the application in complex environment.

Comprehensive assessment of the degree of flooding of soil-cutting working bodies (on the example of plow shares)

Studying the wear process of shares operating in an abrasive environment on the soils of meadow, light and typical gray soils, the parameters of the limiting state are analyzed and it is revealed that the main parameters that contribute to the rejection of shares are the parameters of the occipital chamfer. It is also noted that maintaining a generalized index of blade rejection creates an opportunity to generally assess the degree of wear of the blade, for all changing parameters at the same time and quantify it. This facilitates the assessment of the quality state of the wear of the blade, not only of an individual, but also of groups of compared working bodies. According to this indicator, by conducting a comparative assessment of various designs and working conditions (or tests), it is possible to determine the weakest of them in terms of bluntness or the most abrasive working environment of the working bodies.

Martian regolith—Ti6Al4V composites via additive manufacturing

AbstractIn order to investigate the in‐space in situ resource utilization, directed energy deposition (DED)‐based additive manufacturing (AM) has been utilized to process Martian regolith—Ti6Al4V (Ti64) composites. Here we investigated the processability of depositing 5, 10, and 100 wt% of Martian regolith premixed with Ti6Al4V using laser‐based DED, analyzing the printed structure via X‐ray diffraction, Vicker's microhardness, scanning electron microscopic imaging, and wear characteristics utilizing an abrasive water jet cutter to simulate abrasive environments on the Martian surface. The results indicate that the surface roughness and hardness of the composites increase with respect to the Martian regolith’ weight percentage due to in situ ceramic reinforcement. For instance, i5‐wt% addition of Martian regolith increased the Vicker's microhardness from 366 ± 6 HV0.2 for as‐printed Ti64 to 730 ± 27 HV0.2 while maintaining similar abrasive wear performance as Ti6Al4V. The results point toward laser‐based AM for fabricating Ti64—Martian regolith composites with comparable properties. The study also reveals promising results in limiting the mass burden for future space missions, resulting in cheaper and easier launches.

Forecasting the resource of console-fixed parts during wear with account of permissible stresses

BACKGROUND: Often, parts of the working bodies of machines operating in abrasive environments have a cantilever mount. Due to wear, their dimensions are lost, specified by the technical conditions, and destruction occurs. The resource of these products is determined by the allowable bending stresses, taking into account the intensity of their wear. The existing theoretical methods for predicting the operating time of a part to its limiting state when solving problems do not take into account the criteria of strength and wear in the complex.
 AIMS: The aim consists in obtaining a mathematical expression that determines the resource of the part when it is worn, taking into account the allowable stresses.
 METHODS: The disclosure of the goal was carried out by solving the problem of predicting the resource of a cantilever-fixed using the classical course of the resistance of materials, ele-ments of the theory of elasticity and the basics of tribotechnics.
 RESULTS: As a result of mathematical research and based on practical knowledge, a formula was obtained for determining the resource of a part, which takes into account the dimensions of the part, the magnitude of the allowable stresses, the coefficient regulating the resistance of the material to wear, the pressure on the working surface, the pressure at the pinch point and the pres-sure at the free end timber. The conditions determined by two inequalities are established under which the part will be operable.
 CONCLUSION: Mathematical expressions have been obtained that make it possible to predict and the conditions for the performance of cantilever-fixed parts in the process of their wear ac-cording to allowable stresses have been determined.

Evaluation of the degree of abrasive particles activity in oil of machine units involved in the wear process of toothed wheels

This article discusses the regularities of changes in the activity of abrasive particles in the oil of machine units participating in the process of gear-wheel wear at constant and increasing concentrations. They vary depending on the number of loading cycles of gear teeth, considering the share of crushed abrasive particles in one loading cycle of the gear teeth. This makes it possible to obtain regularities in the change of concentrations of active abrasive particles in the oil depending on the gear modules and the number of loading cycles, taking into the account the fraction of crushed abrasive particles per cycle of loading the gear. This technique can be used to determine the duration of the test of the gear wheel material on samples at a constant total concentration of abrasive particles in the oil change for the units of machines with gear drives operating in the presence of abrasive particles in the working environment. The case under consideration corresponds to the operating conditions of the gear transmission in the unit, which allows calculating the oil change period in the units of machines operating in an abrasive environment.