Mechanical Abrasion Resistance Research Articles

Microstructure analysis of martensitic low alloy carbon steel samples subjected to deformation dilatometry

Low alloy martensitic steels are commonly used in structural and wear resistant applications due to their excellent mechanical properties and abrasion resistance. Martensite phase is generally achieved by rapid cooling, and prior deformation in the austenite region also affects the martensite transformation. It is important to understand the martensite transformation when there is deformation above Ae3. Deformation and quenching simulations have been performed using dilatometry on a low alloy carbon steel. The aim was to determine the influence of deformation above Ae3 (prior deformation) on, firstly, the austenite grain size and shape, and secondly, the martensitic microstructure and variant selection. In addition, the hardness of the martensitic structure due to prior deformation has been investigated. The experimental results obtained from electron backscatter diffraction and microhardness tests on the deformation dilatometry test samples were analysed. The orientation relationship Kurdjumov-Sachs has been used to analyse the martensitic variants. The results revealed a deeper understanding of prior austenite grain structure's effect on the martensitic transformation kinetics and its morphology. The martensite laths' misorientation interval 15–48° were used to visualise the prior austenite grain size. The martensitic lath structure is more refined due to increased prior deformation. Shorter martensite formation time promotes a single dominating packet within the prior austenite grain.

Every midwife matters

Low alloy martensitic steels are commonly used in structural and wear resistant applications due to their excellent mechanical properties and abrasion resistance. Martensite phase is generally achieved by rapid cooling, and prior deformation in the austenite region also affects the martensite transformation. It is important to understand the martensite transformation when there is deformation above Ae3. Deformation and quenching simulations have been performed using dilatometry on a low alloy carbon steel. The aim was to determine the influence of deformation above Ae3 (prior deformation) on, firstly, the austenite grain size and shape, and secondly, the martensitic microstructure and variant selection. In addition, the hardness of the martensitic structure due to prior deformation has been investigated. The experimental results obtained from electron backscatter diffraction and microhardness tests on the deformation dilatometry test samples were analysed. The orientation relationship Kurdjumov-Sachs has been used to analyse the martensitic variants. The results revealed a deeper understanding of prior austenite grain structure's effect on the martensitic transformation kinetics and its morphology. The martensite laths' misorientation interval 15–48° were used to visualise the prior austenite grain size. The martensitic lath structure is more refined due to increased prior deformation. Shorter martensite formation time promotes a single dominating packet within the prior austenite grain.

Facile fabrication of superhydrophobic copper hydroxide coated mesh for effective separation of water-in-oil emulsions

Recently, the super-wetting materials for separating oil/water emulsions have attracted great attention. Developing a low-cost and high-efficient filter material that is challenging to separate stable oil/water emulsions efficiently. In this work, the superhydrophobic copper hydroxide coated mesh was successfully fabricated through a facile spraying and surface modification approach. The excellent separation property of the as-prepared material with efficiency greater than 99.0% under the driving of gravity. Furthermore, the as-developed SCM retained the favorable recyclability and excellent stability even after 10 reuses. More importantly, the SCM exhibited excellent mechanical abrasion resistance after 50 abrasion cycles with sandpaper, which could still remove water from emulsions and possessed excellent separation efficiency. Therefore, the newly developed materials with special wettability have excellent potential in practical use and provide a novel perspective for preparation of stable emulsions separation materials.

Water Resistance Modification of Magnesium Oxychloride Cement with H<sub>3</sub>PO<sub>4</sub>/Na<sub>2</sub>O·xSiO<sub>2</sub>·nH<sub>2</sub>O

Magnesium oxychloride cement (MOC) possesses rapid hardening, high mechanical strength, abrasion resistance, low alkali and low corrosive performances. However, its disadvantages of poor water resistance, easily deformation, moisture absorption and halogenations limit the application. A low cost-effective modifier H3PO4/Na2O·xSiO2·nH2O was designed for MOC system. The results showed that the softening coefficient of the modified MOC reaches 0.988 by adding appropriate dosage of the modifier. Gelatinous substances in the modified MOC was produced after soaking in water, which effectively inhibit the hydrolysis of phase 5 (5Mg (OH)2·MgCl2·8H2O) and the formation of Mg (OH)2, thus improving the water resistance of MOC system. Keywords: Magnesium oxychloride cement; Water resistance; Phosphoric acid

Preparation and Characterization of <i>In Situ</i> Nanocomposites of Graphene Nanosheets/Polyurethane

Graphene nanosheets/polyurethane (GNS/PU) was prepared in situ by polymerization technique for the manufacture of PU safety shoes soles. The graphene nanosheets/polyurethane composites were characterized for their mechanical properties, thermal conductivity and abrasion resistance, and comparison is made with those of the neat polyurethane. The microstructural properties of GNS/PU were characterized by SEM. The results show that with the increase of the amount of graphene within the range of weight-percentages analyzed, the tensile strength of the composites gradually increases. The tensile strength of the GNS/PU composites increased to 64.14 MPa with 2 wt% GNS, compared with 55.1 MPa for neat PU. When the graphene sheets reached 2 wt%, the abrasion volume reached 71 mm3. Compared with the pure PU, the wear performance of GNS/PU composites was significantly improved.

Crosslinking behavior and enhanced mechanical properties of acrylonitrile‐butadiene rubber composites by incorporating aluminum ammonium sulfate particles

ABSTRACTThe crosslinked structure formed by the metal coordination bonding provides excellent and new properties for rubber materials. Herein, the crosslinking of acrylonitrile‐butadiene rubber (NBR) is induced by introducing aluminum ammonium sulfate (NH4Al(SO4)2·12H2O) particles. The crosslinking behavior, morphology, mechanical properties, and the Akron abrasion resistance of NBR/NH4Al(SO4)2·12H2O composites were fully explored. The results show that the three‐dimensional crosslinking structure is held together by metal–ligand coordination bonds between the nitrile group and AI(III). The coordination crosslink density exhibits a considerable increase with the addition of NH4Al(SO4)2·12H2O. Thus, the mechanical properties and abrasion resistance of the obtained composites are better than that of NBR/sulfur system. Interestingly, the elongation at break for NBR/NH4Al(SO4)2·12H2O composites is over 2000% due to the nature of coordination bonds. The abrasion volume loss decreases to 0.4 cm3 for NBR/NH4Al(SO4)2·12H2O composites with 20 phr NH4Al(SO4)2·12H2O particles as compared to 0.75 cm3 for NBR/sulfur system. The obtained NBR composites with facile preparation and excellent mechanical properties make the composites based on metal coordination bonding attractive for practical use. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 879–886

Lightweight Geopolymer Concrete Containing Recycled Plastic Beads

Utilizing recycled plastic beads (RPB) as lightweight waste aggregates in the concrete and geopolymer application is quite attractive. This study presented the mechanical behavior, density, porosity, water absorption, abrasion resistance, thermal conductivity, and ultrasonic pulse velocity (UPV) of geopolymer lightweight concrete containing RPB. River sand in each mixture was replaced by various proportions of RPB ranging between 0-100% by weight. Sodium hydroxide concentration of 15 M, activator solution to fly ash ratio (L/A) of 0.40, sodium silicate and sodium hydroxide ratio of 1.0, and aggregate to fly ash ratio of 1.0 were used throughout the experiment. The results indicated that the replacement of sand by 25% and 50% of RPB had a positive impact on the weight, density, water absorption, and thermal insulating property. The strength and density of the concretes met the minimum requirements of structural lightweight concrete according to ASTM C330.

Properties of pervious concrete incorporating recycled concrete aggregates and slag

Abstract The properties of pervious concrete made with recycled concrete aggregates (RCA) were investigated. Natural aggregates were replaced by RCA at levels of 0, 10, 20, 40, 70, and 100%. Slag was also incorporated to enhance the performance and sustainability of the concrete mixtures. Slump, hardened density, total void content, porosity, permeability, compressive strength, tensile splitting strength, flexural strength, and abrasion resistance were determined. Results showed that the RCA replacement led to an increase in total void content, porosity, and permeability, while a decrease in slump and hardened density was noted. The mechanical properties and abrasion resistance were adversely affected due to the weak RCA and aggregate-mortar interface. The clogging potential of pervious RCA concrete was also assessed over a simulated 20-year lifespan. Permeability could be restored to acceptable, but lower, levels through pressurized water washing. RCA limited the restoration of permeability of pervious concrete, while slag facilitated it. Analytical models were developed to correlate physical, transport, mechanical, and durability properties. Codified equations were assessed for their applicability. Experimental findings highlight the ability to use pervious RCA concrete in pavement applications.

Reversible Coordinative Chain Transfer Polymerization of Butadiene Using a Neodymium Phosphonate Catalyst

This study involves an investigation of the chain transfer reaction of butadiene (Bd) polymerization, under the neodymium tris[bis(2-ethylhexyl)phosphate] (Nd)/diisobutyl aluminum hydride (Al)/ethylaluminum sesquichloride (Cl)/Bd catalytic system. The results show that the chain transfer reaction itself is reversible. Only chain propagation and chain exchange reactions occurred during the later period of polymerization, and there was a linear relationship between the molecular weight and the conversion rate. All polymer chains showed sufficient reactivity to propagate by reacting with the monomer. The degree of the chain transfer reaction can be determined by the amount of Al, and the molecular weight in the synthetic polybutadiene can be accurately designed by the formula Mn=54·Bd/Nd/(0.67Al/Nd-7.17). The catalyst-polymerized butadiene afforded products featuring a relatively narrow molecular weight distribution and a high cis-1,4 stereospecificity. One of these products, polybutadiene rubber, showed narrow distribution in the sample, and exhibited good physical and mechanical properties, low abrasion, and low rolling resistance.

Effect of partial substitution of alumina–chromium slag for Al2O3 on microstructures and properties of Al2O3–SiC–C trough castables

Alumina–chromium slag (ACS), a cheap and abundant refractory raw material comprising aluminum–chromium oxides and β-Al2O3, is a byproduct of ferrochrome smelting. For this reason, we investigated the relationships between composition and mechanical properties, abrasion resistance, oxidation resistance, and resistance to iron slag erosion for Al2O3–SiC–C trough castables in which ACS was substituted for alumina. Due to the presence of β-Al2O3 in ACS, the aluminum-chromium slag reacted with SiO2 to form a low-melting phase of albite and promoted the formation of mullite, which filled the pores at high temperatures and reduced the porosity, thereby promoting densification and strengthening of the sample. The cold mechanical properties of the sample and the normal temperature wear resistance were enhanced, but the high-temperature mechanical properties and the resistance to iron slag corrosion of the sample were impaired. According to the results of the anti-oxidation experiment, the presence of β-Al2O3 in the ACS reduced the porosity and made the sample more dense, which remarkably improved oxidation resistance of the sample. For industrial production requirements, ACS substitution should not exceed 48 wt% due to of thermomechanical properties and anti-slag corrosion performance in Al2O3–SiC–C trough castables.

Water absorption of wood-polymer composites of savewood

The materials based on wood-polymer composites (WPC) in the form of decking boards are produced, in which wood filler is partially replaced by mineral one. WPC materials manufactured by Savewood using a matrix polymer of polyvinyl chloride (PVC) have good mechanical properties, low abrasion and satisfactory resistance to climatic influences. However, they have relatively high water absorption, the task of reducing which is relevant not only in Russia, but also in other countries where there are constructions of facilities operating in outdoor environmental conditions. The modification of such materials in this work was carried out by replacing part of the wood filler with the mineral filler, which is CaCO3 (chalk). Partial replacement of wood flour with mineral filler resulted in a marked reduction in swelling from 1.25 to 0.01%. In this case, the modulus of elasticity is increased from 2260 to 2880 MPa, tensile strength from 30.5 to values of 16.7 ÷ 32 MPa. The specific impact strength varies from 8.90 to 7.74 kJ/m2. The optimal ratio of wood and mineral fillers is 60/40%.

Nature-Inspired and "Water-Skating" Paper and Polyester Substrates Enabled by the Molecular Structure of Poly(γ-stearyl-α,l-glutamate) Homopolypeptide.

We demonstrate that the molecular structure of a synthetic homopolypeptide that resembles the leg architecture of water strider insects is effective to impart flexible polymeric surfaces with superhydrophobic behavior. Filter paper (FP) and polyester (PET) were modified with a coating consisting of low-molecular weight α-helical poly(γ-stearyl-α,l-glutamate) (PSLG, Mw = 4500 Da) homopolypeptide. PSLG-coated substrates displayed near to and superhydrophobic behavior (≥150°) as reflected by the contact angle values. Despite being physically adsorbed, the PSLG coating uniformly covered and was strongly adhered to the substrate surfaces. The thin coating layer displayed remarkable mechanical abrasion resistance and was insensitive to long-time exposure to ambient conditions. PLSG-coated textile fibers exhibited useful and interesting properties. Under an iron-containing load, PSLG-coated PET was able to float and "walk" on water when exposed to a magnet. The PSLG coating was able to reduce the adhesion of Escherichia coli, model Gram-negative bacteria. The results indicated that the molecular geometry of PSLG homopolypeptide, which possesses a α-helical backbone sprouting out of highly hydrophobic stearyl side chains, was the key feature responsible for the observed behaviors. This study is relevant for a broad range of potential applications: from crop and drinking water management in arid geographic areas to biomedical devices and implants.

Effect of filler type and content on mechanical properties and microstructure of sand concrete made with superfine waste sand

In this paper, superfine waste sand generated in waterway regulation engineering was used as the main raw material to produce sand concrete. The effects of ground granulated blast-furnace slag (GGBS) and fly ash (FA) on the mechanical properties, abrasion resistance, and microstructure of sand concrete were measured and compared. The results show that the mechanical properties of sand concrete increase and then decrease with increasing filler content. The optimal filler/sand (F/S) ratios of sand concrete using GGBS and FA fillers are 0.13 and 0.11, respectively. With 300 kg/m3 of cement content, the incorporation of 200 kg/m3 and 150 kg/m3 of GGBS and FA filler, respectively, results in maximum compressive strengths of 36.1 MPa and 30.5 MPa, respectively, at 28 days, and the corresponding splitting tensile strengths are 3.03 MPa and 2.15 MPa, respectively. This optimum mix with weight losses of 6.58% and 8.01% for GGBS and FA fillers, respectively, presents an excellent abrasion resistance. Furthermore, the test results of scanning electron microscopy and mercury intrusion porosimeter indicate that sand concrete with the GGBS filler has higher amount of hydrate products and lower porosity than that with FA. These findings verify the potential usage of sand concrete made with superfine waste sand as a substitute for ordinary concrete in local hydraulic engineering.

Pyrolyzing preceramic polymer into ceramic reverses the wettability of the extreme wetting surface and enhances mechanical abrasion resistance

We introduced a new organic compound to prepare extreme wetting surfaces, and determined that the wettability of the surfaces could be controlled by the curing temperature. Carbon nanotubes were dispersed in the polysilazane ethanol solution to obtain a stable suspension, and an extremely wet coating was prepared on the surface of the sample through impregnation. When cured at 400 °C, the coating was superhydrophobic, but when cured at 800 °C, the wettability was reversed and the coating exhibited superhydrophilicity. Additionally, in order to improve the mechanical abrasion resistance of extreme wetting surface, we design a novel preceramic, polytitanium-silazane, to control the pyrolytic product. Polytitanium-silazane was produced after polysilazane was modified with titanium and a TiN ceramic was obtained after polytitanium-silazane was pyrolyzed at 800 °C. Moreover, hydrophilicity was considerably enhanced than that before modification. Its contact angle was approximately 0°, and a 5-μL droplet of could be completely spread on the surface in 0.2 s.

Physical and chemical effects of siliceous particles at nano, micro, and macro scales on properties of self-consolidating mortar overlays

The aim of this experimental investigation is to study the effect of siliceous particle at nano (0, 1, and 2% of pyrogenic nanosilica), micro (silica fume with 0, 5, and 10% cement weight replacement), and macro scales (sand with SiO2 percentages of 0, 50 and 100%) on mechanical properties, durability, and surface characteristics of self-consolidating mortars as an overlay. For this purpose, 27 self-consolidating mortar overlays (SCMOs) with a water to cement ratio of 0.4 and different mixture proportions were prepared. Mini-slump flow and V-funnel time values were determined experimentally in fresh SCMOs. Moreover, the compressive and flexural strength of mechanical strength, water absorption, porosity, abrasion resistance (as a durability property), skid resistance (as a surface characteristic), and early age shrinkage were measured. The interfacial transition zone and the microstructures were studied using scanning electron microscope (SEM), thermogravimetric analysis (TGA), and atomic force microscope (AFM). Based on the results, the synergic effect of silica based particles in nanoscale and microscale improved mechanical, durability, and frictional properties. SEM images showed that samples containing limestone sand had denser interfacial transition zone (ITZ) than siliceous sand samples due to better interlocking. Using the AFM images, high-silica sand mortar samples exhibit lower skid resistance compared to limestone type sand. Besides, incorporating siliceous sand improves the abrasion resistance (as a durability factor of the slip resistance) about 45.8% compared to lime-based samples. In addition, improvement in wear resistance caused by mineral additions is reduced by increasing the SiO2 percentage in the sand. The relation among porosity, compressive strength, and abrasion resistance was stronger in limestone type mixtures.

Feasible fabrication of a wear-resistant hydrophobic surface

In this study, a novel facile method, namely liquid-phase laser ablation, was proposed to obtain a robust hydrophobic surface. The cemented carbide sample was immersed in a fluorosilane solution and ablated by laser, while controlling the distance between the top surface of sample and liquid level. Then, a surface with good hydrophobicity could be obtained by one step using this technique. The effect of different laser processing parameters on the wettability of the sample surface was studied, and the water contact-angle (WCA) and the rolling angle (RA) could reach 148.4° ± 0.6°, 4.5° ± 0.5°, respectively, which indicated excellent hydrophobicity. Moreover, we found that the hydrophobic surface fabricated by the new method was more wear-resistant than that obtained by the laser texture and fluorination treatment. The hydrophobic surface exhibited excellent mechanical abrasion resistance as it maintained hydrophobicity even after being subjected to mechanical abrasion by hand-polishing 600 times with 1200 grit metallographic sandpaper. Moreover, the mechanism of wear-resistant was analyzed, which was attributed to the formation of the self-healing hydrophobic coatings with a certain thickness on the microstructures. This facile and low-cost method can not only be easily extended to other materials but also produce hydrophobic surfaces with robustness and self-healing properties.

Environmental evaluation, hydration, pore structure, volume deformation and abrasion resistance of low heat Portland (LHP) cement-based materials

Low heat Portland (LHP) cement is one type of low energy and emission cement. In this work, the abrasion resistance, heat releasing properties, shrinkage behavior and pore structures of LHP cement-based materials are comprehensively investigated, and compared with those of moderate heat Portland (MHP) cement and PC ones. The utilization of LHP cement instead of Portland cement (PC) can effectively reduce the energy consumption (14.1%–15.3%) and CO2 emission (14.9%–15.7%) of concrete. LHP concrete shows the highest final compressive strength among three types of concrete mixtures in this study, which consequently leads to the strongest abrasion resistance. The slow developments of autogenous and drying shrinkage of LHP concrete are exhibited. LHP cement paste possesses better early crack resistance than MHP and PC ones due to its lower shrinkage strain at early age. Besides, the hydration heat of LHP cement paste and adiabatic temperature rise of LHP cement concrete are lower than those of MHP cement and PC ones in all hydration ages. In addition, LHP cement paste has a more refined porous structure than MHP cement and PC ones at late ages, which makes the microstructure of LHP concrete denser and improves the final mechanical properties and abrasion resistance to some degree.

Hierarchical Carbon Nanotube@SiO2-TiO2 Reinforced Polyurethane Composites: Thermal, Mechanical and Abrasion Resistance Properties

ABSTRACTIn this study, novel polyurethane-based composites reinforced by hierarchical CNTs@SiO2-TiO2 were fabricated via in situ polymerization. Significant improvement of the composites in thermal stability was achieved by incorporating functionalized CNTs up to 2.0 wt%. Meanwhile, the tensile strength, strain-at-break, and Young’s modulus were greatly improved by increasing nanotube loading. The Abrasion losses could be significantly decreased to 30 mm3/1.61 km due to the addition of functionalized CNTs. Therefore, the introduction of nanosized hierarchical SiO2-TiO2 coated CNTs has a stimulative effect on the simultaneous mechanical reinforcement and abrasion resistance modification for polyurethane.

Analysis of materials used for Greenhouse roof covering - structure using CFD

Greenhouse is widely used to create a suitable environment for the growth of plant. During summer, high temperatures cause harm to the plant. This work calculates characteristics required to optimize the above-mentioned parameters using different roof structure covering materials for the greenhouse. Moreover, this work also presents a simulation of the cooling and heating system. In addition, a computer model based on Ansys Fluent has been using to predict the temperature profiles inside the greenhouse. Greenhouse roof structure shading may have a time-dependent effect the production, water and nutrient uptake in plants. An experiment was conducted in the emirate of Dubai in United Arab Emirates to discover the impact of different materials in order to have an optimal plant growth zone and yield production. These structures were poly ethylene and poly carbonate sheets of 2 different configurations. Results showed that poly carbonate sheets configuration of optimal thickness has given a high result in terms of yield production. Therefore, there is a need for appropriate material selection of greenhouse roof structure in this area of UAE. Major parameters and properties need to be considered while selecting a greenhouse roof structure are the resistance to solar radiation, weathering, thermal as well as mechanical properties and good abrasion resistance. In the present study, an experiment has been conducted to find out the material suitability of the greenhouse roof structure in terms of developing proper ambient conditions especially to minimize the energy lose by reducing the HVAC and lighting expenses. The configuration verified using the CFD, so it has been concluded that polycarbonate can be safely used in the greenhouse than other roof structure material having white or green colour.

Design and Development of Denim Fabrics with Improved Strength and Impact Abrasion Resistance for Motorcyclist Clothing

This study aims to design and develop denim fabrics with enhanced mechanical and impact abrasion resistance performance using different materials, yarn types and fabric constructions. It was aimed to reach the standard impact abrasion resistance requirements of motorcycle protective clothing for Level 1 in high impact areas of the body (zones 1 and 2), such as hip and knee areas. The existence of cotton/Cordura® yarn in warp and T400 polyester yarn in the weft and the use of higher yarn densities increased the performance in tensile strength and impact abrasion resistance, compared to a classical cotton denim fabric. The use of coarser yarns and fabrics with a double weave construction increased impact abrasion resistance compared to single layer cloths. The double and backed cloth samples developed with cotton/Cordura® and Kevlar®/polyester yarns in their construction showed impact abrasion resistance times over 4 s and reached the “EN 13595-2:2002 Level 1 abrasion resistance” standard requirement.