Impact Abrasion Research Articles

Bimodal Particle Reinforcement for Wear Resistant Powder Metallurgy Steels

Reinforcement of powder metallurgy steels with fused tungsten carbide (FTC) has been shown to improve the wear resistance under certain loading conditions. A weakness is however the low hardness of the matrix, which results in selective wearing of the matrix between the carbide particles, i.e. “washing-out” effects. In the present study, in a first round fine metallic or carbidic particles were added to the iron-graphite powder mix, and the blends were die compacted and sintered in protective atmosphere. The specimens were then tested under different wear loads. It showed that also metallic powders added were transformed into carbides during sintering, thus resulting in reinforcement by fine carbides. Since Mo alloying proved to be most effective with regard to hardness and strength, specimens Fe-3%Mo-0.8%C reinforced with 20% coarse FTC (all in mass%) were sintered and tested according to ASTM G65, Continuous Impact Abrasion and dry sliding against ball bearing steel. It showed that Mo addition had quite pronounced positive effect on the G65 erosion resistance and, somewhat less, on dry sliding, while wear resistance in CIAT was less affected; the basic wear mechanisms however remained unchanged.

A Novel Test Method to Determine the Wear Resistance of Agricultural Cutting Tools with an Analyzing Method Based on an Ellipse-Fit Algorithm

Cutting belongs to the essential techniques in many fields of application in agricultural engineering. Cutting tools in agriculture are exposed to a high amount of abrasive wear and impact stress. Increasing the wear resistance of cuttings tools has a high significance for the efficiency and profitability of agricultural machinery. Blunt and deformed blades decrease the energy efficiency and the cutting quality. Blade failures cause machine breakdowns and increase labor and material costs. To enable a consistent and systematic optimization of the blades, a suitable testing method is necessary. Conventional field tests do not provide comparable and repeatable results. Therefore, a test method developed at the FMDauto in cooperation with the Ennepetaler Schneid- und Mähtechnik (ESM) GmbH & Co. KG is presented. The test bench provides standardized and repeatable conditions with a similar wear pattern which is found during field operations. One of the remaining challenges is a clear wear characterization. Existing analyzing methods do not consider the energy efficiency and do not determine the edge holding property clearly. In this paper, a new analyzing method based on an ellipse-fit method is introduced to rate the geometrical shape of the cutting edge and examine the wear resistance of different blades.

The effect of impact conditions on the wear and deformation behavior of wear resistant steels

The deformation and wear behavior of four high strength wear resistant steels were studied in various impact conditions to evaluate their performance in applications involving heavy impacts and impact–abrasion. In the normal direction impacts, the studies were conducted with single and repeated (multiple) drop tests. To better simulate the actual application conditions, the samples were positioned at an angle relative to the impact direction in the tests with the high velocity particle impactor (HVPI) device. The effect of strain rate was investigated using constant size projectiles made from materials with different density but keeping the impact energy constant by varying the incident projectile velocity. The effect of surface hardening on the wear resistance of the high strength steels was determined by impacting the same surface area multiple times at a constant velocity using spherical high velocity projectiles. Regardless of the rather similar hardness of the studied three martensitic steel grades, the impact behavior showed differences in wear rate and damage mechanisms in each case due to the microstructural characteristics of the materials. The adiabatic shear bands forming in the martensitic steels at higher loading rates were found to increase the wear rate. Moreover, the carbide reinforced steel performed in general better than the martensitic grades but showed more brittle behavior and generation of crack networks that can affect the wear performance of the material.

Wear resistance and selection of steels, hardmetals and hardfacings for abrasive wear conditions

Hardness and toughness have a major effect on wear resistance. The material wear rate depends directly on hardness (at sliding wear), as well as on material toughness (at impact wear). The main goal of the present work was to study the abrasive wear behaviour of different wear resistant steels, hardmetals/cermets and hardfacings. The following steels were under the study: a) hardenable boron and non–alloy steel C 45 subjected to different heat treatments; b) hardened steels Hardox 400…600. WC–Co hardmetals and TiC–NiMo cermets and composite metal–matrix coatings were studied. The abrasive wear tests were performed using two methods: a) abrasive rubber–wheel wear; b) abrasive impact wear. The dependence of wear resistance on hardness and toughness of steels is clarified, the wear maps are composed. In combined abrasive/impact wear conditions, composite materials/coatings with multimodal reinforcements show promising results in increasing of abrasive wear resistance of rapidly wearing wear parts.

Effect of Structural Characteristics on Abrasive Wear Resistance and Impact Strength of Facing and Carbonitrided Coatings

Abrasive wear of metallic materials, depending on their hardness, may occur by two mechanisms [1]. With respect to low hardness material if H m /H a < 0.7 (H m and H a are material and abrasive hardness, respectively), wear occurs by a microcutting mechanism when wear particles are separated as a result of repeated action of an abrasive body on a worn surface. With greater material’s hardness, microcutting does not occur and wear happens as a result of repeated plastic or elastic deformation of surface volumes. Wear resistance increases by several factors. During wear of relatively soft materials by a microcutting mechanism, their wear resistance is directly proportional to integral hardness. With wear by a plastic deformation mechanism, the material’s wear resistance is not uniquely determined by hardness. In this case, apart from hardness, a greater and sometimes important role determining the level of wear resistance is played by structural and fatigue properties of worn material. There are numerous indicators about the existence of these connections [1, 2]. It is generally accepted that the greatest wear resistance is exhibited by materials with a multiphase (heterophase) structure impregnated with hard and refractory phases: carbides, nitrides, borides, etc. Differences in wear resistance of these materials are due to the type of inclusions, the amount of them, dimensions, and shape. The type of metal matrix and its properties, mainly hardness and toughness, also affect heterophase structure wear resistance. Representation of the effect of structure of metallic materials on wear resistance and impact strength may be obtained from results of analyzing tests for service properties of faced iron-chromium alloys [3]. The microstructures of some alloys, arranged in an order of increasing carbon content, and their characteristics are presented in Table 1. The least wear resistance under abrasive wear conditions applies to hypoeutectoid alloys (1 and 2) having a ferritepearlite or martensite-austenite structure. Hypereutectoid alloys (3 and 5), whose structure is represented by a continuous carbide network, have high hardness and wear resistance compared with the first alloys, although they are distinguished by extremely low impact strength.

Assessing the abrasion resistance of cores in virgin and recycled aggregate pervious concrete

Abrasion resistance of pervious concrete was evaluated on core and cast specimens by using the Rotating-Cutter method and the Impact Abrasion method. Sixteen mixtures were produced using limestone, pea gravel, and recycled concrete aggregate, and up to 30% of cement was replaced by ground granulated blast-furnace slag. The analysis of the core specimens indicated that the Impact Abrasion method had a low within-test coefficient of variation and was able to differentiate among mixtures. The use of recycled aggregate and ground granulated blast-furnace slag did not have a detrimental effect on the abrasion resistance of pervious concrete.

Mechanically robust, thermally stable, broadband antireflective, and superhydrophobic thin films on glass substrates.

In this study, we developed a simple and versatile strategy to fabricate hierarchically structured lotus-leaf-like superhydrophobic thin films. The thin films are broadband antireflective, and the average transmittance of coated glass substrates reached greater than 95% in the wavelength range of 530-1340 nm, in contrast to 92.0% for bare glass substrate. The thin film surface shows a static water contact angle of 162° and a sliding angle less than 4°. Moreover, the thin film is thermally stable up to 300 °C, and shows remarkable stability against strong acid, strong alkali, water drop impact, and sand impact abrasion, while retaining its superhydrophobicity. Further, the thin film can pass the 3H pencil hardness test. The current approach may open a new avenue to a variety of practical applications, including windshields, eyeglasses, windows of high rise buildings and solar cells, etc.

Characterization of Impact Abrasive Wear Produced by Different Rocks

In industry, core components such as crushers, miner feeder devices and impact stone breakers are exposed to heavy wear which involves mechanisms such abrasive wear and / or impact abrasion. The purpose of this work is to identify complex wear mechanisms that occur in such conditions and to correlate them with the properties of typical abrasives found in mining environments.

High Temperature Cyclic Impact/Abrasion Testing of Boiler Steels

In the present study the high temperature impact/abrasion resistance of several boiler steels which are used in Estonian power plants were determined experimentally using the High Temperature Cyclic Impact Abrasion Test (HT-CIAT) at 500 and 600°C. Results indicate a strong dependence of the wear resistance on the materials microstructure and formation of the mechanically mixed layer with incorporated abrasive particles.

Abrasive Wear Resistance of HVOF Sprayed and PTA-Welded Hardmetal Hard Phase Reinforced Metal-Matrix Based Coatings

The aim of the current study was to elaborate and compare abrasive wear resistance of thick metal matrix based deposited coatings. To produce metal matrix composite (MMC) coatings, experimental powders made by mixing commercial nickel and iron based powders with recycled hardmetal powder were used. The usage of recycled hardmetal as an initial material can significantly decrease the cost of production, improve the mechanical characteristics of coatings and consequently increase their wear resistance. Based on structural studies the optimal content of 40 vol% hard phase was selected. Plasma transferred arc (PTA) hardfacing and high velocity oxyfuel (HVOF) spraying were used as deposition technologies. The behavior of coatings by abrasive rubber wheel wear (ARWW ) (based on G 65 standard), abrasive impact wear (AIW) and abrasive erosion wear (AEW) (based on GOST standard) was investigated. The results showed that the wear resistance of experimental PTA hardfacings at high angle impact wear conditions is notably higher than of HVOF sprayed coatings.

Wear Mechanisms on Martensitic Steels Generated by Different Rock Types in Two-Body Conditions

The main purpose of this work is to identify and describe complex wear mechanisms that usually occur in the mining environment. Abrasive conditions can differ a lot, especially in the mining industry. Therefore, the need to study the influence of abrasion conditions on the material wear is crucial in order to improve the lifetime and the cost efficiency of the machinery used in such environments. To study various abrasion mechanisms, a cyclic impact abrasion test was used to simulate two-body impact/abrasion. The tests were performed using two martensitic steels, and three different standard rock types of the mining environment were chosen as abrasives, respectively. The wear was indicated as mass loss by measuring the samples before and after the tests. On the other hand, the particle breakage index, which indicates the potential of a rock to wear, was observed by sieving the abrasives before and after the test. The wear results were correlated with different mechanical rock properties. Wear mechanisms were observed using microscopic investigations. The results indicate that different abrasive rock types have a significant influence on the wear rate of the tested martensitic steels. It was observed that by combining different rocks as abrasives, a simulation of the real field was achieved.

Structure and properties of HVOF-sprayed and PTA-welded cermet hard phase reinforced Fe-matrix-based coatings

The aim of this study is to elaborate new composite coatings based on the hardmetal/cermet hard pahase metallic–iron–based matrix for the heavy abrasive wear conditions. WC–based hardmetal and Cr–based cermet powders, produced by disintegrator milling, were used. Commercial Cr–Ni–steel and FeCrSiB alloy powders were used as matrix materials. Optimal content of hard phase (40 vol.%) was selected. For deposition of coatings, high–velocity oxy–fuel (HVOF) spraying and plasma transferred arc (PTA) hardfacing were used. Three different wear testing methods namely abrasive rubber wheel wear (ARWW), abrasive erosive wear (AEW) and abrasive impact wear (AIW) were studied. Wear rates and relative wear resistance values were determined. As a result, the advantages of experimental composite coatings in comparison with commercial powder–based coatings were demonstrated.

Testing the mechanical resistance of timber used for construction in the marine environment

The paper describes refinements of rapid laboratory assessment of the mechanical performance of timbers used in the marine environment as regards their resistance to indentation, impact abrasion from smooth and sharp abrasives and to dynamic impact loads when wet. Ten tropical and home-grown hardwoods, five softwoods and a wood–polymer compound were examined. Brinell hardness, dynamic hardness, abrasion resistance, and the structural integrity in high-energy multiple impact tests were determined comparatively on dry and wet specimens. A trend was shown where softwoods show a decrease in abrasion resistance with wetting, whilst hardwoods did not. In dry conditions, impact abrasion using steel balls was higher than when using sharp grit. It is suggested that when wet, water in the cells has a hydraulic energy absorbing effect.

Abrasive wear mechanisms and their relation to rock properties

Wear caused by abrasion is the predominant factor in mining industry. Abrasive wear is a rapid and severe process due to the contact between abrasives and solid material surfaces. This type of wear is usually classified into two categories: (i) 2-body abrasive wear and (ii) 3-body abrasive wear according to the type of contact that occurs between the abrasives and the material. The tribological system formed in mining environment embraces both abrasive wear categories. The focus of this paper is to bring in detailed focus the 2-body and 3-body wear behaviour based on correlations which point out some physical and mechanical rock properties having a significant influence. The study was based on three different rock types wearing a typical martensitic steel 42CrMo4 (DIN 1.7225) under 2-body conditions using a Cycling Impact Abrasion Test (CIAT) and 3-body conditions using a Slurry Steel Wheel Abrasion Test (SSWAT). Results showed that tested rocks perform totally different when the testing conditions are changed. Furthermore, the specific wear energy under 3-body conditions was calculated in order to gain understanding regarding energy needed to produce wear.

Research on the Optimization of Heat Treatment Process and the Abrasive Impact Wear Mechanism of 70Mn Steel

This research was conducted on the influence of heat treatment parameters on the mechanical properties and abrasive wear resistance of 70Mn steel through experimental results. Orthogonal experiment was applied for designing heat treatment process and acquired optimal heat treatment parameters. The experimental results showed that the optimum heat treatment process was firstly heated to 830°C preserved for 60min, and rapidly quenched, then tempered at 200°C for 80min. Abrasive impact wear experiment was performed on MLD-10 tester, under which the wear surface and the subsurface were observed through scanning electron microscope and optical microscope. According to the experimental result, abrasive impact wear mechanism was analyzed. The results showed that plastic deformation fatigue and gouging wear were the primary mechanisms of abrasive impact wear, together with a small amount of furrow and cutting.

Impact–abrasion wear characteristics of in-situ VC-reinforced austenitic steel matrix composite

In this investigation, in-situ precipitation of vanadium carbides was employed to reinforce Fe–13Mn and Fe–13Mn–3W alloys by means of conventional melting and casting route. Microstructures were characterized by optical and scanning electron microscopy techniques.Mechanical properties of the materials were determined by hardness, impact toughness and tension tests. It was observed that tungsten improved the strength of the matrix and the reinforcements as well as tensile properties and work hardening rate of the VC-reinforced composite. Ball mill abrasion test was utilized to simulate impact–abrasion wear condition using two types of abrasive minerals. The results showed that the degree of benefit to be gained by the use of in-situ VC-reinforced composite materials depends strongly on crush strength of the abrasives. It was found that the studied particle-reinforced composite materials were only advantageous when the abrasives were relatively soft, providing low-stress abrasion condition.

Strength and Freeze-Thaw Testing of Lightweight Aggregate Concretes

This investigation indicates the effects of freeze-thaw cycles on the strength development and durability of lightweight aggregate concretes. Two lightweight aggregate concrete, one normal concrete and one reactive powder concrete were used in this study, and total four types of concrete mix were named NC, LWC1, LWC2, and RPC. Before and after freeze-thaw test, the samples were evaluated by the compressive strength, fflexural strength, and impact abrasion tests. The test results show that steady decrease in compressive and flexural strength after freeze-thaw testing for most concrete specimens. The lightweight aggregate used in the LWC1 mix for this laboratory study had a good freeze-thaw performance history, but the LWC2 mix with lightweight aggregate approaching the 24-hour water absorption had a bad result. It might be due to the void volume required to release hydraulic pressure developed during cyclic freezing.

Abrasive impact wear and surface fatigue wear behaviour of Fe–Cr–C PTA overlays

The conventional Fe–Cr–C overlay is studied due to the lack of information regarding the response of this material system to impact wear conditions. Previously the same material system has been successfully used in erosion wear conditions. The high stress abrasive impact wear resistance and low and high surface fatigue wear behaviour of a Fe–Cr–C overlay (FeCrC—matrix) produced by plasma transferred arc welding (PTA) were studied.The overlays with varied PTA hardfacing process cooling parameters were tested. The cooling parameters were as follows: (1) active cooling—application of gas cooling of substrate during the welding process; (2) passive cooling—application of copper plate under substrate with constant temperature of 20°C and (3) standard—cooling in the air. Different cooling time leads to differences in microstructure and formation of residual stresses (surface cracks, etc.).The abrasive impact testing reveals the difference in the overlays response to the cyclic stressing at high impact energy. The surface fatigue wear (SFW) testing is accompanied by the abrasive impact wear (AIW) testing. The SFW incorporates cyclic loading of the overlays surface with spherical indenter with radius of 10mm at high loads, while in AIW testing the specimens are bombarded almost in normal direction with granite gravel particles (diameter of <6mm) with the energy in the range of 0.14–0.52J.The study proposes the relation between high energy impact/abrasive wear behaviour and the surface fatigue wear behaviour of Fe–Cr–C hardfacings produced under varying cooling conditions.

Factors That Influence Failure Behaviour and Remaining Useful Life of Mining Equipment Components

Mobile mining equipment often operates in harsh environments characterised by remote locations and highly variable rock and operating conditions. This research explores the hypothesis that the failure behaviour of mining equipment is influenced by the physical properties of the ore and waste. We describe a method of examining this relationship via data mining on maintenance records and apply it to the hydraulic cylinders of two classes of earthmoving mobile equipment. Failure data for the analysis are drawn from maintenance work orders from 14 sites mining for haematite iron, nickel sulphide, and coking and thermal coal. The results show that the distributions of the estimated life parameters for hydraulic cylinders on earthmoving equipment are distinctly different for haematite iron, coal, and nickel sulphide sites. Analysis of the relationship between selected physical properties identified the influence of rock impact hardness number, abrasion index, and absolute hardness of the ore as significant factors for these hydraulic cylinders. Their effects are significant when parameters are considered in combination, for example, rock impact hardness number and abrasion index, and vary according to the cylinder type and asset class. The engineering implications of these results are considered with respect to known failure modes of the cylinders.

Modification of the mechanical and chemical properties of dental enamel using Er laser radiation with sub-ablative energy density

AbstractLasers can be successfully used for the modification of biological tissues. In dentistry, an increase in strength and the chemical properties of enamel with a laser in order to prevent tooth decay appears to be quite promising. We investigated microhardness and acid resistance of human tooth enamelEnamel of the tooth crown was investigatedThe measured microhardness of intact enamel of human tooth crown wasIn this paper it was found that sub-ablative YLF:Er laser radiation modifies the intact enamel in such a way that the enamel microhardness increases and can exceed the intact enamel microhardness by 20%. Laser-treated enamel can resist abrasive impact during a time equivalent to 3 years of standard dental hygiene. Laser-treated enamel can resist an external aggressive medium containing 37.5% phosphoric acid significantly longer than intact enamel. The observed improvement in the mechanical and chemical properties of the enamel can be explained by a significant reduction in enamel porosity after laser radiation impact.