The effect of boron on the abrasive wear behavior of austenitic Fe-based hardfacing alloys

The effect of boron on the abrasive wear behavior of the austenitic Fe–Cr–C–Si–B hardfacing alloys was investigated with varying boron concentration. It was found that the abrasive wear resistance of the hardfacing alloys increased up to 50% compared to that of boron-free alloys with increasing boron concentration. The mechanism of the abrasive wear resistance changed at 0.6 wt.% boron. Below 0.6 wt.% boron concentration, the abrasive wear resistance was improved almost linearly and strain-induced martensitic transformation was considered as the controlling factor for improving the resistance. Above 0.6 wt.% boron, it was observed that the primary borides started to precipitate. Further increase in boron concentration was not able to enhance the resistance due to the negligible change of primary borides’ size and volume fraction. With these results, it was concluded that two different effects of boron on the wear resistance of the austenitic Fe–Cr–C–Si–B hardfacing alloys existed depending on the boron concentration.     

Guidelines for the selection of hardfacing alloys for sliding wear resistant applications

The work presented in this report summarizes an evaluation of the relative sliding wear characteristics of several commonly used commercial hardfacing alloys. The alloys studied include cobalt-base, nickel-base and Fe-Cr-Ni alloys which also contain small amounts of cobalt. Selecting the most effective alloy combination to withstand sliding wear is a challenge for materials engineers, equipment designers and fabricators. Accurate guidelines for selecting compatible alloys from a wear resistance point of view are not available. On the basis of the results of this work several hardfacing alloy combinations were identified which provide good sliding wear resistance. In addition, several hardfacing alloy combinations were found to exhibit poor wear resistance compatibility. The guidelines presented in this report will aid in the selection of suitable hardfacing alloy combinations with adequate sliding wear resistance. The wear guidelines are also supplemented with corrosion data in several environments of importance in the chemical process industries. These data should assist in the selection and optimization of hardfacing alloys in the presence of aggressive environments.     

Sliding wear performance of cobalt-based alloys in molten-Al-added zinc bath

Pin-on-disk sliding wear tests were conducted in a molten Zn-18% Al (wt.%) bath at 470°C to evaluate the wear performance of as-cast Stellite 6 and Tribaloy 800, and PTA (plasma transferred arc) well-surfaced Stellite 6 with 35% and 50% WC-Co. Wear performances of PTA weld-surfaced Stellite 6 with 35% WC-Co and 50% WC-Co are not effective when coupled with the same materials although their hardnesses are the highest compared to other materials tested. When Tribaloy 800 is coupled with PT35 (PTA weld-surfaced Stellite 6 with 35% WC-Co) and PT50 (PTA weld-surfaced Stellite 6 with 50% WC-Co), only Tribaloy 800 would be damaged and part of worn Tribaloy 800 would be transferred to the counterpart PT35 or PT50 materials regardless of disk and pin combinations. Although overall wear rates of both pin and disk are similar between Stellite 6 and Tribaloy 800, the wear mechanism is quite different. While harder eutectic carbides are broken and detached in Stellite 6, the softer matrix is preferentially attacked without pulling out harder phases in Tribaloy 800 during the wear testing.     

AZ91D镁合金在水介质下的冲击磨损特性研究

研究了AZ91D镁合金在冲击载荷和去离子水介质综合作用下的磨损特性.结果表明,镁合金表面冲击斑深度及面积随冲击次数的增加而增加;冲击磨损初期,损伤的主要形式为塑性变形及粘着磨损,随着表面塑性耗竭,微观疲劳裂纹产生;磨损后期,水介质的腐蚀作用明显,加速了材料表面的损失.     

Sliding wear behavior of dedicated iron-based SLS materials

Systematic investigation of wear behavior of selective laser sintering (SLS) materials is lacking in SLS/selective laser melting research. The present research is an effort to fill the gap by performing sliding wear tests under plastic and elastic contact conditions upon proprietary iron-based SLS materials: LaserForm and DirectSteel. It is found that LaserForm is a better SLS wear material. It is concluded that wear performance is governed not by the hardness of the materials but by their composition.     

Sliding wear behavior of mesocarbon microbeads based carbon materials

The sliding wear behavior of mesocarbon microbeads (MCMBs) based carbon materials was investigated. Samples were sintered at 1300 °C from pure MCMBs without ball-milling (C0) and ball-milled MCMBs doped with 3, 5, 10 wt.% nano-SiC (C3, C5 and C10). The results indicated that C0 sample had poor sliding wear property; ball-milling and doping nano-SiC contributed to the improvement of sliding wear property. The mean friction coefficient values of the C0–C10 samples against H62 brass alloy were 0.38, 0.24, 0.21, and 0.30, respectively. Mass loss increased with increasing sliding time, and C0 and C3 had the highest and lowest mass loss, respectively. The worn surface images showed C0 sample had broad wear tracks and was free from debris layer, while the worn surfaces of C3 and C5 were rather smooth because of the formation of adherent contact films without any significant fracture. These good sliding wear properties were related to small grains, uniform high hardness and large amount of aromatic layers along contact surface.     

Sliding wear behavior of planar random zinc-alloy matrix composites

The friction and wear behavior of planar random zinc-alloy matrix composites reinforced by discontinuous carbon fibres under dry sliding and lubricated sliding conditions has been investigated using a block-on-ring apparatus. The effects of fibre volume fractions and loads on the sliding wear resistance of the zinc-alloy matrix composites were studied. Experiments were performed within a load range of 50–300 N at a constant sliding velocity of 0.8 m s⁻¹. The composites with different volume fractions of carbon fibres (0–30%) were used as the block specimens, and a medium-carbon steel used as the ring specimen. Increasing the carbon fibre volume fraction significantly decreased the coefficient of friction and wear rates of both the composites and the medium-carbon steel under dry sliding conditions. Under lubricated sliding conditions, however, increasing the carbon fibre volume fraction substantially increased the coefficient of friction, and slightly increased the wear of the medium-carbon steel, while reducing the wear of the composite.Under dry sliding conditions, an increasing load increased not only the wear rates of both the composite and the unreinforced zinc alloy, but also those of their corresponding steel rings. However, the rate of increase of wear with increasing load for both the composite and its corresponding steel ring was much smaller than for the unreinforced zinc alloy and its corresponding steel ring. The coefficient of friction under dry sliding conditions appeared to be constant as load increased within a load range of 50–150 N for both the composite and the unreinforced zinc alloy, but increased at the higher loads. Under any load the coefficient of friction of the composite was lower than half that of the unreinforced zinc alloy under dry sliding conditions.     

Sliding wear behavior of protective coatings for diesel engine components

The use of heat-insulating ceramic coatings on the cylinder walls of diesel engines is currently being considered for certain advanced engine designs. Since a major consideration in such an application is the wear resistance of the coatings, a series of tests has been carried out to determine the sliding wear behavior of several pairs of candidate materials systems, initially at room temperature. The tests were performed using a washer-on-disc specimen configuration and an oscillatory rotation movement to simulate the motion of a piston ring on a cylinder wall. It was determined that each material tested had a different pattern of sliding wear behavior. Impregnation of plasma-sprayed Y₂O₃-ZrO₂ with chromia markedly improved its wear resistance.     

Effects of temperature and sliding distance on the wear behavior of austenitic Fe-Cr-C-Si hardfacing alloy

The effects of temperature and sliding distance on the metal-to-metal wear behavior of austenitic Fe-20Cr-1.7C-1Si hardfacing alloy were investigated in air in the temperature range from 25 to 450 °C. The applied contact stress was 55 MPa and the maximum sliding distance was 18 m. In the temperature range from 25 to 200 °C, the weight loss increased linearly with increasing sliding distance. The weight loss increased parabolically with increasing sliding distance up to 18 m at 300 °C, but at 450 °C, the weight loss drastically increased from the beginning of the wear test and became almost saturated above a sliding distance of 3.6 m. The initial friction coefficient was not changed with temperature up to 300 °C. However, at 450 °C, the initial friction coefficient increased abruptly. It was thought to be due to the increasing tendency of adhesive bonding to occur between the two self-mating specimens. At temperatures below 200 °C, the steady state friction coefficient did not change significantly. Above 300 °C, the steady state friction coefficient decreased due to the oxide layers that formed on the worn surfaces during wear.     

Effect of temperature on wear behavior of high-entropy alloys

The wear behavior of a FeCoNiCrMn (counterbody)–Ti₃₀Zr₂₅Hf₁₅Nb₂₀Ta₁₀ (finger) friction pair in the temperature range of 77–873 K has been determined. It has been found out that the finger wear significantly decreases with an temperature increase compared with the counterbody due to the spur increase in the hardness of the friction surface structures of up to 18.0 GPa due to the formation of a high-temperature oxide. It has been revealed that the depth of secondary structures increases with temperature, while at 523 K and higher, it reaches 40 μm.     

Reduction of wear via hardfacing of chisel ploughshare

The objective of this study was to increase the wear resistance by covering the chisel ploughshare produced from low-alloy steel with three different hard facing electrodes. Comparative wear tests on a regular share and three kinds of hardfacing with electrodes were conducted in the field and laboratory. These three different hardfacing electrodes, which are designated EH-600, EH-350 and EH-14Mn, were used for hardfacing. The wear rate in the laboratory and in field tests was found to be significantly different statistically. When the cost is taken into consideration; EH-600 and EH-350 have been found to be the best hardfacing electrodes.     

The microstructure and galling wear of a laser-melted cobalt-base hardfacing alloy

A carbon dioxide laser was used to modify the surface of a Stellite 156 weld overlay that had been deposited using a plasma transferred arc. Conditions were identified that resulted in a crack-free surface. The modified surfaces were characterized using optical microscopy, microhardness measurements and scanning electron microscopy-energy-dispersive X-ray analysis. Galling wear resistance was determined using a pin-on-plate test. Pre- and post-test surface roughness values were determined with a profilometer. Laser-induced melting led to a significant increase in microhardness, a significant reduction in grain size and a more uniform distribution of alloying elements in the cobalt-rich matrix and the carbide precipitates. However, the galling wear resistance of the lasermelted specimens was unchanged from that measured on untreated specimens.     

The comparison of wear properties of different Fe‐based hardfacing alloys in four kinds of testing methods

Iron‐based hardfacing alloys are widely used to protect machinery equipment. A strong correlation is given between microstructure and chemical composition of welding deposit with the resulting wear behaviour. Concerning precipitation of metallurgical hard phases and synthetic added hard particles, the bonding strength of the hard phases in the metallic matrix seems to play a dominating role to obtain high wear resistance. The main objective of this study was to evaluate the wear behaviour for pure abrasion, combined impact/abrasion and high impact wear, respectively, for four different Fe‐based hardfacing alloys. Tests were performed with a standard ASTM G65 dry‐sand/rubber‐wheel tester. An impeller–tumbler apparatus enabled investigation of impact abrasion wear tests. Additional wear tests with high impact loading were performed on a drop hammer apparatus. Fracture surface analysis was carried out after drop hammer testing and results were correlated with microstructure and interfacial bonding behaviour of precipitations in metallic matrix. Copyright © 2008 John Wiley & Sons, Ltd.     

Sliding wear behavior of Fe-based bulk metallic glass at high temperature

In the past decade Fe-based bulk metallic glasses (BMGs) have attracted increasing attention due to their beneficial properties, including high glass forming ability (GFA), high strength and hardness and high fracture toughness in both fundamental science and engineering application. Most research using these materials has been conducted at room temperature environment, and research that assesses their behavior especially at high temperature has been scarce. We present the results of high temperature effect on the friction and wear behavior of Fe-based bulk metallic glass (BMG), and we tested that this material may satisfy wear and oxidation resistance at high temperature as well as to explore the high temperature wear mechanism of the Fe-based BMG. The dry sliding tribological behaviors of Febased BMG against Si₃N₄ ceramic were conducted with a pin-on-disc friction and wear tribometer. The morphology of the worn surfaces of Fe-based BMG was examined by scanning electron microscopy (SEM) and the chemical composition characterized with energy dispersive spectroscopy (EDS) to observe the wear characteristics and investigate the wear mechanisms. The overall average friction coefficient value generally decreased with increasing temperature, and the glass transition and the formation of protective oxide film played an important role in the tribological behavior of BMG. The wear resistance of Fe-based BMG was not only from their hardness but also from the formation protective oxide layer. Analysis of the worn surface revealed abrasion, plastic deformation and oxidation during sliding test.     

Reduction of mouldboard plough share wear by a combination technique of hardfacing

This paper presents comparison of wear of regular mouldboard plough shares and two plough shares made of different basic materials, steel EN 10027 (HF-1) and EN 50Mn7 (HF-2), hardfaced by a combination of two welding processes, namely shielded metal arc welding (SMAW) and high-frequency induction welding (HFIW). Wear was determined by measurements of the changes of dimensions and weight during ploughing of sandy clay soil in Croatia. The dimensions and weight losses were lower for both types of hardfaced plough shares in comparison to regular shares, and lower fuel consumption and a higher rate of work were achieved with hardfaced plough shares. Hardfaced plough shares also offer lower production costs in comparison to regular plough shares. According to the overall results, this protection method can be recommended as an efficient solution for plough share wear protection.     

Sliding wear behavior of nanocrystalline nickel coatings: Influence of grain size

In the present study the sliding wear behavior of pulse electrodeposited nanocrystalline Ni coatings as a function of grain size including bulk annealed Ni has been systematically studied using pin-on-disc configuration against the WC-Co counter body. The sliding wear has been analyzed with respect to wear rate, coefficient of friction, subsurface deformation and composition of wear debris. The result indicates that the sliding wear rate and coefficient of friction of Ni decreases with decreasing grain size. The subsurface beneath the worn pin surface is composed of a near surface shear region and beneath it a region of bulk plastic deformation. The ratio of the depth of the shear region to the depth of bulk deformed region decreases with decreasing grain size indicating a greater localization of near surface deformation with decreasing grain size.     

Sliding wear behavior of electron beam surface-melted 0–2 tool steel

Studies were carried out on the dry sliding wear behavior of electron beam melted surface layers on a type 0–2 tool steel and on annealed and conventionally hardened 0–2 steel specimens for comparison. Wear tests were conducted in a flowing argon atmosphere at a sliding speed of 20 cm s^?1 and a load of 10 N against a 52100 bearing steel ring. Wear surface morphology was studied along with subsurface structure using optical and electron microscopy methods. The study concentrated on the wear of this steel after different processing treatments. Electron beam surface melting and subsequent rapid solidification in situ of the steel produced a highly refined martensitic microstructure having higher hardness values and better wear resistance than obtained using conventional quench hardening of that steel. Carbide distribution and martensite phase morphology were affected by this surface melting process; those microstructural characteristics influenced the wear behavior. Variations in electron beam power and surface speed during melting were explored in terms of their effect on the resulting surface layer. The wear test system used was computer interfaced and controlled, permitting continuous measurements of wear depth and friction force.     

钛基化学镀耐磨涂层微动磨损性能研究

以提高钛合金抗微动磨损性能为宗旨,研究了化学镀Ni-Tl-B（NTB）三元合金及Ni-Tl-B/BN、Ni-Tl-B/SiC复合镀层制备工艺,利用X射线衍射技术、扫描电镜及能谱分析等手段,分析了三种镀层的结构,观察了镀层表面形貌,利用微动摩擦磨损试验机评价了化学镀处理对钛合金抗磨的影响,实验结果表明：该工艺得到的Ni-Tl-B、Ni-Tl-B/BN、Ni-Tl-B/SiC多元复合镀层表面光亮、质感均匀、镀层结合力良好,经过相同次数微动磨损试验,Ni-Tl-B镀层的耐磨性能比TA7及Ni-Tl-B/BN、Ni-Tl-B/SiC镀层好。     

Sliding wear of polymeric composites

The wear mechanisms of two different polymeric composites sliding against metal were investigated experimentally. The sliding distance, normal force and sliding speed were the test variables.Microscope observations showed that the mode of wear of the two materials is similar. Subsurface deformation, crack nucleation at the matrixharder particle or matrix-glass fibre interface, crack propagation parallel to the surface at a depth corresponding to the friction coefficient and crack shearing to the surface were found in both materials. The wear particles often have the shape of thin sheets. Comparison of the metal subsurfaces and wear particles with those of the polymers indicates that the mechanism of wear of semicrystalline composites is similar to delamination wear. Since film transfer greatly influences friction and wear it should be considered together with crack growth in fatigue in the prediction of wear of polymeric composites.