Abrasive Environment Research Articles

Effect of abrasive particle size on slurry abrasion resistance of austenitic and martensitic steels

The effects of the abrasive particle size and the pH-value of the aqueous solution on the abrasive wear resistance of H–13 steel and Hadfield steel were investigated. Abrasive wear tests, using a wet rubber wheel abrasion tester, were carried out applying abrasive sizes in the range of 0.15–2.40mm. The pH-values of the aqueous solution ranged from 5.5 to 12.8. The microstructure of each material was characterized with optical microscopy. The wear surfaces and the wear particles (debris) were analyzed by scanning electron microscopy (SEM). The macro- and microhardness were measured before and after the wear tests using a Vickers hardness tester. The surface topography of the wear scars was examined by a non-contact 3D profiler in order to measure the depth of the abrasive penetrations.The results demonstrated that Hadfield steel is more wear resistant than H-13 steel for all pH-values and all abrasive particle sizes used in the tests. Moreover, the micro-hardness of the wear scar surface of the Hadfield steel increased significantly with the size of the abrasive grain, while this increase was lower for the H-13 steel. The greater work-hardening of the austenitic Hadfield steels was considered to be responsible for this higher wear resistance in comparison with the martensitic H-13 steel. For both materials the loss of mass increased linearly up to a critical abrasive particle size (CPS); this CPS, the mass loss continued to increase but with a lower gradient. An explicit effect of the steel matrix on the mass loss behavior as a function of the abrasive grain size was not observed. The less acidic aqueous solution resulted in lower mass losses for both materials and for all abrasive grain sizes. This effect was greater for the two smaller abrasive grain sizes. For higher pH-values, lower depths of penetration of the abrasive particles were observed. The analysis of the wear particles in all test conditions displayed continuous and discontinuous chips for the H-13 steel but only discontinuous chips for the Hadfield steel,. For both materials two abrasive wear micromechanisms were determined: microcutting and microploughing. Finally, the results presented in this work suggest that the wear performance analysis of Hadfield steel, to be used in an abrasive environment, should consider the effects of the pH value of the aqueous solution and the abrasive particle size.

Effect of small addition of Cr on stability of retained austenite in high carbon steel

High carbon steels with dual phase structures of martensite and austenite have considerable potential for industrial application in high abrasion environments due to their hardness, strength and relatively low cost. To design cost effective high carbon steels with superior properties, it is crucial to identify the effect of Chromium (Cr) on the stability of retained austenite (RA) and to fully understand its effect on solid-state phase transition. This study addresses this important knowledge gap. Using standard compression tests on bulk material, quantitative X-ray diffraction analysis, nano-indentation on individual austenitic grains, transmission electron microscopy and electron backscatter diffraction–based orientation microscopy techniques, the authors investigated the effect of Cr on the microstructure, transformation behaviour and mechanical stability of retained austenite in high carbon steel, with varying Cr contents. The results revealed that increasing the Cr %, altered the morphology of the RA and increased its stability, consequently, increasing the critical pressure for martensitic transformation. This study has critically addressed the elastoplastic behaviour of retained austenite – and provides a deep understanding of the effect of small additions of Cr on the metastable austenite of high carbon steel from the macro- to nano-level. Consequently, it paves the way for new applications for high carbon low alloy steels.

Effect of thermal spray coatings on wear behavior of high tensile steel applicable for tiller blades

A rotary tiller is a mechanized agricultural implement popularly used to save time, human effort and fuel in preparation of soil bed. The tiller blades are subjected to extreme surface wear under complex abrasive environments. The aim of this study was to improve the service life of the tiller blade by means of three different thermal spray coatings. Stellite-21, WC-Co-Cr and Cr3C2-NiCr coating powders were deposited on high tensile steel which is being used for tiller blades by pulsed detonation spray technique and wear behavior of these coatings were evaluated by pin-on-disc mechanism at ambient temperature under dry conditions in accordance with ASTM G-99 standard. It was observed that WC-Co-Cr coating on high tensile steel has provided higher wear resistance in abrasion in comparison to Cr3C2-NiCrand Stellite-21. Scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDAX) and X-ray diffraction (XRD) techniques were used to analyze the worn out surfaces.

Simulation of soil-cutting blade wear in an artificial abrasive environment based on the similarity theory

This article considers the conditions for creating the soil-cutting blade wear model proceeding from abrasive wear mechanics. The basic determiners of the nature and rate of blade wear are identified. The influence of external factors is considered that are related to power consumption for overcoming the soil resistance to destruction. The soil resistance forces include the ones that deform the soil at compaction, and the inertia forces that originate at the uplift and displacement of the soil layer. The necessary and sufficient conditions for creating a model similar to natural in the domain of desired properties are considered. The similarity criteria of the model-nature system are determined that characterize the processes observed during the blade wear in actual soil conditions. The numerical values of the similarity criteria determined for the model are identical to the natural loamy soil.

Comparison of scratch resistance of lamellar and compacted graphite irons used in cylinder liners

Linear scratch tests were performed on polished surfaces extracted from different cylinder liners, manufactured in lamellar and compacted graphite irons. The effect of wall thickness was evaluated, by extracting samples from regions equivalent to two levels of thickness. Scratch geometry was analyzed using 3D interferometry, in terms of pile-up proportion and widths of tracks, and wear mechanisms were revealed under a scanning electron microscope. Overall friction coefficients could be related to the deformation of metallic matrix and the graphite count, while graphite affected the scratch geometry, especially their widths along the sliding distance. The larger variation and higher friction amongst the tested materials were observed for compacted graphite iron, extracted from the thick wall. The observed wear mechanisms were also verified in worn components subject to abrasive environments.

Stability of retained austenite in high carbon steel under compressive stress: an investigation from macro to nano scale.

Although high carbon martensitic steels are well known for their industrial utility in high abrasion and extreme operating environments, due to their hardness and strength, the compressive stability of their retained austenite, and the implications for the steels’ performance and potential uses, is not well understood. This article describes the first investigation at both the macro and nano scale of the compressive stability of retained austenite in high carbon martensitic steel. Using a combination of standard compression testing, X-ray diffraction, optical microstructure, electron backscattering diffraction imaging, electron probe micro-analysis, nano-indentation and micro-indentation measurements, we determined the mechanical stability of retained austenite and martensite in high carbon steel under compressive stress and identified the phase transformation mechanism, from the macro to the nano level. We found at the early stage of plastic deformation hexagonal close-packed (HCP) martensite formation dominates, while higher compression loads trigger body-centred tetragonal (BCT) martensite formation. The combination of this phase transformation and strain hardening led to an increase in the hardness of high carbon steel of around 30%. This comprehensive characterisation of stress induced phase transformation could enable the precise control of the microstructures of high carbon martensitic steels, and hence their properties.

A Comparative Study on Graphene Oxide and Carbon Nanotube Reinforcement of PMMA-Siloxane-Silica Anticorrosive Coatings.

Carbon nanotubes (CNTs) and graphene oxide (GO) have been used to reinforce PMMA-siloxane-silica nanocomposites considered to be promising candidates for environmentally compliant anticorrosive coatings. The organic-inorganic hybrids were prepared by benzoyl peroxide (BPO)-induced polymerization of methyl methacrylate (MMA) covalently bonded through 3-(trimethoxysilyl)propyl methacrylate (MPTS) to silica domains formed by hydrolytic condensation of tetraethoxysilane (TEOS). Single-walled carbon nanotubes and graphene oxide nanosheets were dispersed by surfactant addition and in a water/ethanol solution, respectively. These were added to PMMA-siloxane-silica hybrids at a carbon (CNT or GO) to silicon (TEOS and MPTS) molar ratio of 0.05% in two different matrices, both prepared at BPO/MMA molar ratios of 0.01 and 0.05. Atomic force microscopy and scanning electron microscopy showed very smooth, homogeneous, and defect-free surfaces of approximately 3-7 μm thick coatings deposited onto A1020 carbon steel by dip coating. Mechanical testing and thermogravimetric analysis confirmed that both additives CNT and GO improved the scratch resistance, adhesion, wear resistance, and thermal stability of PMMA-siloxane-silica coatings. Results of electrochemical impedance spectroscopy in 3.5% NaCl solution, discussed in terms of equivalent circuits, showed that the reinforced hybrid coatings act as a very efficient anticorrosive barrier with an impedance modulus up to 1 GΩ cm(2), approximately 5 orders of magnitude higher than that of bare carbon steel. In the case of GO addition, the high corrosion resistance was maintained for more than 6 months in saline medium. These results suggest that both carbon nanostructures can be used as structural reinforcement agents, improving the thermal and mechanical resistance of high performance anticorrosive PMMA-siloxane-silica coatings and thus extending their application range to abrasive environments.

Turbulence model development for flotation cells based on piezoelectric sensor measurements

Turbulence is an important factor that affects flotation performance, which needs to be incorporated into flotation models. However, the measurement of turbulence in industrial flotation cells is difficult because of the highly abrasive and aggressive slurry environment. This has made the development and validation of models incorporating turbulence difficult. The development of a measurement methodology based on the piezoelectric vibration sensor (PVS) has enabled the measurement of kinetic energy fluctuation in flotation cells. In the study presented in this paper, the PVS was first applied to a sugary water-air two phase mixture in a 3m3 pilot flotation cell, and then to a Metso RCS 3m3 flotation test rig with magnetite/silica slurry and air, to collect turbulence data. An orthogonal experimental design was used for both sets of tests, with different impeller speeds, air flow rates and cell level (aspect ratio) as input hydrodynamic parameters. From the measurement data collected in the two cells, the volume of the turbulence zone could be modelled; from this, the turbulence distribution in the flotation cells could be predicted. The models were validated by comparing the predicted with the experimental results.

High temperature three-body abrasive wear of 0.25C 1.42Si steel with carbide free bainitic (CFB) and martensitic microstructures

In the present work, the wear behaviour of different steels has been investigated under a three body abrasive environment at room and elevated temperatures. High-silicon steel (0.25C–1.42Si) was austempered at 300 and 320°C in order to obtain two carbide-free bainitic steels with different mechanical properties. The same steel subjected to two different quench and temper heat treatments was used as a reference material for mechanical and wear testing. The steels were subjected to three-body abrasive wear by means of a high temperature continuous abrasion tester (HT-CAT). The tests were done at 25, 300 and 500°C respectively. All samples showed similar wear rates at room temperature. At 500°C, the material austempered at 320°C showed the highest toughness and the lowest wear rate. High temperature hardness and impact toughness tests showed that abrasive wear is not only influenced by hardness but also by the toughness of the material. Owing to their good strength/toughness combination CFB steels could prove to be an important material for abrasive wear applications.

Effect of particle characteristics on the two-body abrasive wear behaviour of a pearlitic steel

The specific wear rate and friction coefficient of a pearlitic microstructure subjected to different abrasive environments (i.e. SiC and alumina) were examined. A CSM high temperature pin-on-disc tribometer was used to simulate the two-body abrasive condition (i.e. the metallic surface abrading against the abrasive particles). The characteristics of the abrasive particles (i.e. particle size and density) revealed a significant impact on the amount of material loss. The specific wear rate of the pearlitic microstructure decreased with a reduction in the abrasive particle size, irrespective of the particle type. In addition, distinct particle deterioration mechanisms were observed during the abrasion process, which was largely determined by the abrasive particle size. Attrition, shelling and fracture were some of the dominant particle deterioration mechanisms occurring in both of the abrasive environments. SEM and EDX analysis on the wear debris displayed a unique metallic chip formation with respect to the particle type. Furthermore, the abrading efficiency (i.e. threshold level) of the abrasive particles was identified by means of interrupted abrasive wear tests. The dense packing nature of the alumina abrasive particles resulted in a significantly higher material removal rate than the SiC abrasive environment.

Structure and tribological properties of steel after non-vacuum electron beam cladding of Ti, Mo and graphite powders

The non-vacuum electron beam cladding technique was used to fabricate layers alloyed with Ti, Mo and C on the surface of low-alloyed steel. Two types of experiments were carried out. In the first experiment, a mixture of Ti and graphite powders was used for cladding; in the second, a mixture of Ti, Mo and graphite powders was used for cladding. CaF2 powder or a mixture of CaF2 and LiF powders was used as flux. The thickness of the cladded layers was in the range of 2–2.2mm. The structure of the layers was studied using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The microhardness after cladding of the layers fabricated by cladding of Ti and graphite powders was 8–9GPa, while the microhardness of layers with Mo additions reached 11–12GPa. The highest wear resistance at sliding friction and friction in abrasive environment was reached in the samples fabricated using Ti, Mo and graphite mixture due to the higher hardness and the martensite–austenite structure of the matrix. The wear resistance against fixed abrasive particles was 2.4 times higher compared to that of carburized and quenched steel.

Measuring turbulence in a flotation cell using electrical resistance tomography

Measuring turbulence in an industrial flotation environment has long been problematic due to the opaque, aggressive, and abrasive three-phase environment in a flotation cell. One of the promising measurement techniques is electrical resistance tomography (ERT). By measuring the conductivity distribution across a measurement area, ERT has been adopted by many researchers to monitor and investigate many processes involving multiphase flows. In the research outlined in this paper, a compact ERT probe was built and then used to measure the conductivity distribution within a 60 l flotation cell operated with water and air. Two approaches were then developed to process the ERT data and estimate turbulence-related parameters. One is a conductivity variance method and the other is based on the Green–Kubo relations. Both rely on and use the fluctuation in the ERT measurement caused by bubbles moving through the measurement area changing the density of the fluid. The results from both approaches were validated by comparing the results produced by the ERT probe in a 60l flotation cell operated at different air rates and impeller speeds to that measured using an alternative turbulence measurement device. The second approach is considered superior to the first as the first requires the development of auxiliary information which would not usually be known for a new system.

Optimization of formulation of repair abrasion-resistant dispersion-strengthened epoxy composition with sand filler on the adhesion strength

It is shown that when performing work on the restoration of parts operating in abrasive environment, the formulation containing 60-70 pts. wt. of natural sand and 30-40 pts. wt. of epoxy adhesive is the most effective in terms of adhesion strength.

Plasma nitriding of HP13Cr supermartensitic stainless steel

Supermartensitic stainless steels (SMSS) are commonly employed in the oil exploitation industry and present a good balance between the necessary physical and chemical properties and financial costs. Certain applications, such as in extreme corrosive and abrasive environments, demand improvements in the surface properties of these steels. In the present work, HP13Cr SMSS with a fully martensitic microstructure were plasma nitrided in the 350–450°C range. The high diffusivity and low solubility of nitrogen in the martensitic structure allowed the production of thick layers (16–61μm) containing ɛ-Fe2–3N, γ′-Fe4N and expanded phase (αN) in all the temperatures. In addition, anisotropic sputtering rate and N-diffusion were observed for different grain orientations. Mechanical properties were measured by instrumented indentation, appropriately corrected from roughness effects on the results. Hardness profiles increased from 3.8GPa (bulk) to ∼14GPa (near surface region) in all the working temperatures, whereas the elastic modulus was 230GPa, presenting no statistically significant differences with respect to the bulk value. Nanoscratch tests revealed a hardened-ductile like behavior of these nitride layers. The surface tribo-mechanical behavior was correlated with elastic–plastic responses of the precipitate-containing texturized layers. Results are interpreted in light of the effectiveness of plasma nitriding to modify the surface properties of SMSS.

Determination of wear pattern of cutting elements of tillage machines

The problems of theoretical researches of wear surface of the working tools’ cutting elements of tilling machines are shown in the article. The main aim of the research is to develop a process of hardening, providing increase their longevity and quality of soil treatment. The interaction process of working tools of tilling machines with soil abrasive environment during their movement is characterized by the interaction of abrasive soil on wedge with a flat working surface. This article describes how to influence the impact of soil on a wedge from material deformation nature, the wedge parameters, physical and mechanical properties and soil conditions. The theoretical dependence of these parameters allows to provide the wear of the cutting elements of tilling machines, which will contribute to reduction of the dynamics of their wear. To ensure the longevity of cultivator tooth is necessary reducing the size of their wear is necessary to reduce the ability of abrasive wear out and will provide options of cultivator tooth, which will reduce the dynamics of wear. The research results will select and apply an effective technology of hardening of cutting elements of tilling machines during wear and recovery.

Wear behavior and work hardening of high strength steels in high stress abrasion

High strength steels (HSS) used in highly abrasive environments, such as in mining and crushing, must endure high stress abrasion. To properly understand the wear behavior of materials under such circumstances, the connection between surface loading, work hardening, and material removal has first to be determined. In this study, wear resistant steels with initial hardness ranging from 400 to 750 HV were investigated in single-grit abrasion. In the cyclic abrasion experiments, the abrasion resistance of the steels was improved noticeably from the initial state due to surface hardening. However, the highest surface hardening rate did not result in the highest wear resistance. Moreover, when the surface loading was sufficiently increased, the transition to a high wear rate mechanism was observed.

Three-Body Abrasive Wear Behavior of Needle-Punch Nonwoven Jute Fiber Reinforced Epoxy Composites

Abstract Now-a-days, natural fiber based composites are emerging as a supplement to the synthetic fiber composites. The aim of the present work is to investigate the three-body abrasive wear behavior of needle-punch nonwoven jute fiber reinforced epoxy (NJFE) composites in an abrasive environment. Three-body abrasion studies have been done on composites using rubber wheel abrasion tester. The design of experiments approach using Taguchi methodology is employed for the parametric analysis of abrasive wear process. The effect of the factors such as sliding velocity, fiber loading, applied load, sliding distance and abrasive size on the specific wear rate and coefficient of friction of composite has been studied. Experimental results reveal the improvement of abrasive wear behavior of the composites with the addition of fiber as compared to neat epoxy. At steady state condition, it has been observed that composites with 36 wt% fiber loading shows minimum specific wear rate. From the statistical analysis it has been concluded that the factor combination with sliding velocity of 120 cm/s, fiber loading of 36 wt%, normal load of 10 N, sliding distance of 50 m and abrasive size of 400 μm gives minimum specific wear rate whereas sliding velocity of 144 cm/s, fiber loading of 36 wt%, normal load of 10 N, sliding distance of 70 m and abrasive size of 300 μm gives minimum coefficient of friction. Finally, the worn surfaces are examined by using scanning electron microscopy (SEM) and possible abrasion wear mechanisms are discussed.

Rotary seal solutions offer abrasive options

Russ Pimblett, senior engineer at Garlock Sealing Technologies, argues that while rotary seals may never displace mechanical seals and conventional compression packing in all process applications, they can offer a better option in those that involve abrasion and corrosive environments.

Surface Hardening of Chromium Steel by Controlled Successive Oxynitriding

The process of thermochemical treatment of steel 40Kh13 involving successive stages of oxidizing and oxynitriding is considered. The three-layer modified coating obtained consists of a zone of internal nitriding and a surface nitride zone of a powder-like e-phase, which are separated by a nanosize oxide film. The hardness of the surface after such treatment, the wear resistance of the steel under conditions of abrasive and hydroabrasive wear, and the corrosion resistance in an abrasive environment of an oil-well formation fluid are determined. The process considered is shown to be more advantageous than the traditional nitriding.

Exploring ball size distribution in coal grinding mills

Tube mills use steel balls as grinding media. Due to wear in the abrasive environment it is necessary to charge new balls periodically to maintain a steady balanced ball charge in the mill. The amount and ball size distribution in this charge, as well as the frequency with which new balls are added to the mill, have significant effects on the mill capacity and the milling efficiency. Small balls are effective in grinding fine particles in the load, whereas large balls are required to deal with large particles of coal or stone contaminant. The steady state ball size distribution in the mill depends on the top-up policy.The effect of the ball size distribution on the milling rate of coal has been measured as a function of ball size distribution. The change in ball size distribution as affected by wear and ball top-up policy has been modelled. From this a best ball top-up policy can be recommended that will ensure a close approximation to the desired steady-state ball size distribution that gives the required PF size distribution for the selected mill demand.