Investigations on Microstructures and Two-body Abrasive Wear Behavior of Fe–B Cast Alloy

The microstructures of Fe–B alloys containing different carbon and boron concentrations have been investigated. The solidification microstructures of Fe–B alloy consist of the eutectic boride, pearlite, and ferrite. Borides precipitate along the grain boundary during the formation of eutectic. After heat treatment, the phases in Fe–B alloy are composed of the boride and martensite. With increase of carbon and boron concentrations, the Rockwell hardness of Fe–B alloy becomes larger. Meanwhile, by using a pin-on-disk abrasion tester, the effects of carbon and boron concentrations on the wear behaviors including ploughing depth, roughness, and wear weight loss under different loads have been studied. The results show that the wear resistance of Fe–B alloy with higher carbon and boron concentrations is comparable with the high chromium white cast iron.     

Three-Body Abrasive Wear Behavior of Low Carbon Fe–B Cast Alloy and Its Microstructures Under Different Casting Process

This study investigates the effect of semi-solid processing on the microstructures, mechanical properties of low carbon Fe–B cast alloy. The as-cast microstructure of Fe–B cast alloy consists of the eutectic boride, pearlite, and ferrite. Compared with the coarse eutectic borides in the ordinary alloy, the eutectic boride structures in the semi-solid alloy are greatly refined. Moreover, the boride area fraction, Rockwell hardness, impact toughness, etc., before and after heat treatment under different casting methods are also investigated systemically. The wear behaviors of low carbon Fe–B cast alloy are studied by three-body abrasive wear tester. The wear weight loss of semi-solid Fe–B cast alloy is lower than that of the ordinary Fe–B cast alloy because of the lower average boride area for semi-solid specimen. Meanwhile, the wear mechanism of the low carbon Fe–B cast alloy under different casting process is depicted and analyzed by using the physical models.     

Effects of Chromium Addition on Microstructure and Abrasion Resistance of Fe–B Cast Alloy

This research work studies the effects of chromium on microstructure and abrasion resistance of Fe–B cast alloy. The results show that eutectic boride changes from continuous network to less continuous and matrix changes from pearlite to martensite with the increase in chromium content in the alloy. Meanwhile, an increase in chromium addition in the alloy leads to an increase in the chromium content in M₂B-type boride because chromium can enter boride by substituting for iron in Fe₂B. Under two-body wear, Fe–B cast alloy exhibits excellent wear resistance. When alloys are tested against soft abrasive, chromium can markedly improve the wear resistance of Fe–B cast alloy, whereas excessive chromium can reduce the wear resistance. The wear resistance of Fe–B cast alloy increases first and then decreases with the increase in chromium. But when tested against hard abrasive, since the hardness of SiC is much higher than that of M₂B boride, an increase in chromium content marginally increases the wear resistance. Weight losses of Fe–B cast alloy increase with the increase in the load and exhibit the linear relationship.     

Effect of Melting and Microstructure on the Microscale Friction of Silver–Bismuth Alloys

This article reports an investigation of the effect of melting and microstructure on the microscale friction of several silver–bismuth alloys using a high-temperature nanoindentation-tribotesting system. These studies showed that friction increases with temperature before melting. We modeled these results as due to the softening of the alloys with increasing temperature, which appears to adequately explain the experimental trend. The friction behavior upon melting depends on the alloy composition. For some alloy composition, friction was observed to exhibit a sharp decrease upon melting, while for another alloy composition, friction was observed to keep increasing with temperature. This unusual behavior can be explained by the difference in microstructure and phase composition as a function of temperature among different Ag–Bi alloys.     

The Influence of the Matrix Microstructure on Abrasive Wear Resistance of Heat-Treated Fe–32Cr–4.5C wt% Hardfacing Alloy

The abrasion wear resistance of Fe–32Cr–4.5C wt% hardfacing alloy was investigated as a function of matrix microstructure. In this study, the alloy was deposited on ASTM A36 carbon steel plates by the shielded metal arc welding (SMAW) process and the as-welded matrix microstructure was changed into ferrite, martensite, and tempered martensite by heat treatment processes. The Pin-on-disk test results show that under low (5 N) and high (20 N) load conditions, the wear resistance behavior of the as-welded matrix sample is 20 and 15% higher, respectively, than the martensitic matrix sample, although the bulk hardness of the as-welded matrix is 5% lower. The ferritic matrix sample has the poorest wear resistance behavior which is less than half of that of the as-welded matrix one. Micro-ploughing, micro-cutting, and micro-cracking are recognized as the micro-mechanisms in the material removal in which the proportion of micro-ploughing mechanism increased by increasing matrix toughness.     

The Microstructure and Abrasive Wear Resistance of Fe–Cr–C Hardfacing Alloys with the Composition of Hypoeutectic,Eutectic, and Hypereutectic at $$ frac{Cr}{C} = 6 $$

In this investigation, three Fe–Cr–C hardfacing alloys with different carbon and chromium contents and in constant ratio of ( fracCrC = 6 ) left( {frac{Cr}{C} = 6} right) were fabricated by GTAW on AISI 1010 mild steel substrates. The OES, OM, SEM, and XRD techniques and Vickers hardness method were used for determining chemical composition, hardness, and studying the microstructure of the hardface alloys. The OES, OM, and XRD examination results indicated that different carbon and chromium contents of hardface alloys produced hypoeutectic/eutectic/hypereutectic structures. By increasing the carbon and chromium contents in the chemical composition of hardface alloys, the volume fraction of the total (Cr, Fe)₇C₃ is increased resulting to decreasing in total the austenite volume fraction and increasing the hardness of the surface. Studying the microstructure after wear test (ASTM G65) shows that at the edge of the worn surface, the transformation of austenite to martensite had occurred in all the samples. The wear test results indicate that the highest wear resistance is gained in the hypoeutectic structure with maximum hardness after the wear test. In addition, abrasive wear micromechanisms in hypoeutectic/eutectic/hypereutectic were recognized as: ploughing + cutting/ploughing + cutting + cracking/cracking + cutting, respectively.     

Effects of Ni and Mn on the Cavitation Erosion Resistance of Fe–Cr–C–Ni/Mn Austenitic Alloys

The effects of Ni and Mn concentrations on the cavitation erosion behavior of Fe–12Cr–0.4C–xNi/Mn (x = 5, 7, and 10) alloys were investigated with respect to strain-induced γ → α′ and γ → ε phase transformation. The cavitation erosion resistance of the Ni-added alloys decreased with increasing Ni concentration, whereas that of the Mn-added alloys improved with increasing Mn concentration. Also, the 7Mn-added alloy and 10Mn-added alloy, which additionally underwent the γ → ε phase transformation, had better resistance to cavitation erosion than the 5Mn-added alloy in which the γ → α′ phase transformation occurs most actively. These behaviors were considered to be due to the fact that the strain-induced ε martensite absorbs the cavity collapse energy and prevents the damage by cavitation erosion more effectively than the strain-induced α′ martensite.     

Effect of Aramid Pulp and Lapinas Fiber on the Friction and Wear Behavior of NBR Powder–Modified Phenolic Resin Composite

Short fiber reinforcement plays a definite role in governing the performance of a composite through the improvement of different material properties. The present investigation deals with the effect of aramid pulp and lapinas fiber on the friction and wear characteristics of a composite made from phenolic resin modified by powdered acrylonitrile butadiene rubber (NBR) on a pin-on-disc tribometer. Four composites, containing 10, 20, 30, and 40 wt% of aramid pulp with respect to phenolic resin content, were prepared. Another four composites, containing 50, 100, 200, and 300 wt% of lapinas fiber with respect to phenolic resin content, were also made. It was found that the two different fibers have distinctly different contributions to the friction and wear properties of the composites. It was also found that the incorporation of aramid pulp enhances friction stability of the composites much better than that of lapinas fiber. The change in surface morphology of these composites was studied by scanning electron microscopy (SEM) before and after the friction test. SEM images of friction samples containing aramid pulp corroborated the occurrence of wear through an adhesive wear mechanism, whereas the lapinas fiber–containing composites showed an abrasive wear mechanism.     

Corrosion-Wear Resistance and Interfacial Morphologies of Novel Fe–Cr–B Cast Steels in Molten Aluminum

In order to improve the corrosion–wear resistance properties of steels in molten aluminum, novel Fe–Cr–B cast steels with different boron concentrations were prepared. The steels were investigated at 750 °C for 0.5 h using a ring-block corrosion–wear test, and the interfacial morphologies were examined. Results showed that the corrosion–wear resistance of the Fe–Cr–B cast steel was three times that of H13, and benefited greatly from the effects of the primary Cr-rich Fe₂B, which bore the main load during the corrosion–wear test. The corrosion–wear behavior of the coarse primary Cr-rich Fe₂B in molten aluminum was clearly different from that in static molten aluminum.     

Effect of Tribo-Oxidation on Friction and Wear Behaviour of HVOF Sprayed WC–10Co–4Cr Coating

Tribology Letters - In current investigation, tribological properties of TiAl matrix composite reinforced with 15 vol%Ti2AlN and TiAl alloy prepared through in situ reactive method of...     

The Effect of “Hot-Spot” Temperatures on the Unlubricated Wear of Steel

Experiments are described in which pins of low-alloy, medium-carbon steel are worn against disks of the same material under unlubricated sliding conditions. The friction and wear characteristics of this system are measured as functions of load and speed. The choice of loads and speeds was made in such a way as to obtain the entire range of “hot-spot” temperatures possible for the system. The results are then compared with those to be expected from a model of the wear process in which the wear at the contacting regions between the pin and the disk is closely associated with the oxidation of the metal in these regions. The temperature of oxidation is assumed to be the calculated “hot-spot” temperature. In order to make the results compatible with the proposed model, it is necessary to introduce a new parameter (having the dimensions of length) which is shown to increase steeply with increasing “hot-spot” temperature up to about 700 C. It then levels off, at about 10^?6 cm, for all hot-spot temperatures in excess of about 700 C. In this way, the hot-spot temperature is shown to be a very important variable in the wear of steel.     

Effects of Silicon Content on the Mechanical Properties and Lubricated Wear Behaviour of Al–40Zn–3Cu–(0–5)Si Alloys

In this work, one ternary Al–40Zn–3Cu and seven quaternary Al–40Zn–3Cu–(0.25–5)Si alloys were synthesized by permanent mould casting. Their microstructure, mechanical and lubricated wear properties were investigated using appropriate test apparatus and techniques. As the silicon content increased the hardness of the alloys increased, but their elongation to fracture decreased. Tensile strength of the alloys decreased with increasing silicon content following a sharp decrease and a slight increase. Among the silicon-containing quaternary alloys the highest and the lowest tensile strength values (348 and 305 MPa) were obtained with the Al–40Zn–3Cu–2Si and Al–40Zn–3Cu–5Si alloys, respectively, while the base alloy (Al–40Zn–3Cu) exhibited a tensile strength of 390 MPa. However, the volume loss due to wear of the alloys increased with increasing silicon content after showing an initial increase and a sharp decrease. The lowest wear loss was obtained with the alloy containing approximately 2% Si which has the highest tensile strength among the quaternary alloys containing more than 0.25% Si. Wear surfaces of the alloys were characterized mainly by smearing indicating that adhesion is the dominant wear mechanism for the experimental alloys.     

Inter-relation of Microstructural Features and Dry Sliding Wear Behavior of Monotectic Al–Bi and Al–Pb Alloys

Immiscible Al-based alloys of monotectic composition have a particular feature of minority phases embedded into the Al-rich matrix. The disseminated particles may act as in situ self-lubricating agents due to their lower hardnesses compared with that of the Al-rich matrix, favoring good tribological behavior. There is a lack of systematic fundamental studies on the microstructural evolution of monotectic alloys connected to application properties. In the present investigation, the monotectic Al-1.2wt%Pb and Al-3.2wt%Bi alloys have been chosen to permit the effect of microstructural parameters on the wear behavior to be analyzed. Directional solidification experiments were carried out under transient heat flow conditions allowing a large range of cooling rates to be experienced, permitting a representative variation on the scale of the microstructure to be examined. Samples of the monotectic alloys having different interphase spacing, λ, have been subjected to microadhesive wear tests, and experimental laws correlating the wear volume with the microstructural interphase spacing and test time are proposed. It was found that microstructural features such as the interphase spacing and the morphology of the minority phase play a significant role on the wear process and that for the alloys examined λ exhibits opposite effects on the corresponding wear volume.     

Microstructures and High-Temperature Friction–Wear Performance of Laser-Remelted WC-12Co Coatings by HVOF

A WC-12Co coating prepared by high-velocity oxygen fuel (HVOF) was remelted with a CO₂ laser, and the surface–interface morphologies, plane energy spectrum, and phases of the coating were analyzed by means of field emission scanning electron microscopy (FESEM), energy-dispersive spectrometry (EDS), and X-ray diffraction (XRD), respectively. The friction and wear behaviors of the WC-12Co coating were investigated at high temperature with a wear test, and the morphologies and the changes in chemical elements on the wear scar after the wear test were analyzed with SEM and EDS, respectively. In addition, the influence of high temperature on the coefficient of friction (COF) and wear performance is discussed. The results show that the substrate is closely bonded with the substrate after laser remelting (LR), which includes mechanical bonding accompanied by metallurgical bonding. The average coefficient of friction (COF) at 600, 700, and 800°C is 0.6832, 0.3957, and 0.1922, respectively. The wear mechanisms of WC-12Co coating at 600 and 700°C are adhesive wear, abrasive wear, and oxidative wear, respectively, and the wear mechanism of the coating at 800°C is serious oxidative wear.     

Surface Roughness Effect on the Friction and Wear Behaviour of Acrylonitrile–Butadiene Rubber (NBR) Under Oil Lubrication

Tribology Letters - The artificial cervical disc was simplified and designed as a ball-on-socket model with the material configuration of polymer-on-Ti6Al4V (TC4). The material of polymer ball...     

Effect of 10 wt% VC on the Friction and Sliding Wear of Spark Plasma–Sintered WC–12 wt% Co Cemented Carbides

The effect of 10 wt% VC addition on the friction and sliding wear response of WC–12 wt% Co cemented carbides produced by spark plasma sintering (SPS) was studied. The SPS of WC–12 wt% Co alloys with and without 10 wt% VC, at 1100 and 1130°C, respectively, yielded dense materials with minimal porosity. No eta phase was found in any of the alloys. The WC–12 wt% Co–10 wt% VC alloy showed the formation of a hard WV₄C₅ phase, which improved the alloy's hardness. Friction and dry sliding wear tests were done using a ball-on-disk configuration under an applied load of 10 N and sliding speed of 0.26 m.s^?1, and a 100Cr-steel ball was used as the counterface. A significant improvement in the sliding wear response of the harder and more fracture tough WC–12 wt% Co–10 wt% VC alloy compared to the WC–12 wt% Co alloy was found. Analysis of the worn surfaces by scanning electron microscopy showed that the wear mechanisms included plastic deformation, preferential binder removal, adhesion, and carbide grain cracking and fragmentation.     

Effect of Carbides on Wear Characterization of High-Alloy Steels under High-Stress Rolling–Sliding Condition

This article describes the wear characterizations of high-speed steel composed of vanadium carbide and high-chromium cast iron composed of chromium carbide. These metals were studied under rolling–sliding conditions with a sliding ratio of 10% using a self-made ring–ring wear testing machine. The fine microstructure of carbides and failure behaviors were analyzed by scanning electron microscopy and high-resolution electron microscopy. The results showed that carbide significantly affected the wear properties and failure behaviors of metals. The relative wear resistance of high-speed steel reinforced by vanadium carbides was twice that of high chromium cast iron composed of chromium carbides. Chromium carbide was characterized by a stacking fault substructure, and slips occurred in chromium carbide under high-stress contact, resulting in crack formation. Vanadium carbide was reinforced and pinned by large amounts of nanoparticles, which prevented its dislocation under high-stress rolling–sliding conditions, thereby effectively resisting crack initiation. Furthermore, the (200) lattice plane of vanadium carbide is coherent with the (111) lattice plane of austenite, preventing cracks from forming at the interface of the vanadium–carbide matrix. The morphology and hardness of vanadium carbide also contributed to the excellent wear property of high-speed steel.     

Surface Modification of Machine Parts Made of Iron–Carbon Alloys Operating under Conditions of Friction and Wear

The article has described a promising oxyalloying technique for the surface modification of machine parts made of iron–carbon alloys that operate under conditions of friction and wear. The new method has been implemented via the surface impregnation of steel and cast-iron parts with superheated steam of aqueous solutions of salts containing chemically active alloying elements. A multilayer coating formed on the surfaces of parts as a result of this treatment increases their performance characteristics, which has been confirmed by the integrated research.     

Effects of Strain-Induced Martensitic Transformation on the Solid Particle Erosion Behavior of Fe–Cr–C–Ni/Mn Austenitic Alloys

The effects of Ni and Mn concentrations and also the impact velocity on the solid particle erosion behavior of Fe?C12Cr?C0.4C?CxNi/Mn (x?=?5 and 10) alloys were investigated with respect to strain-induced martensitic transformation. The critical strain energy (CSE), which is defined as the energy required to initiate the martensitic transformation increased with increasing Ni and Mn concentrations. As the impact velocity decreased, the solid particle erosion resistance of the low CSE alloy improved compared to that of the high CSE alloy under the given ranges of impingement angles and impact velocities. This result was most likely due to an increase in the volume fraction of martensite that formed during the solid particle erosion test in the low CSE alloy when the impact velocity was decreased.