Erosive wear of selected metals in coal washing environments

A slurry erosive wear apparatus developed by the authors has been used to test the erosive wear behaviour of selected metals in coal washing environments. The erosive wear test machine was employed to determine the effects of (1) carbon content in carbon steels, (2) chromium content in alloy steels, and (3) corrosion of aqueous solutions on the erosive wear behaviour of metals. The test results revealed that the carbon content in annealed carbon steels slightly affects the erosive wear resistance of metals, while the increase in chromium content of alloy steels apparently improves the erosive wear resistance of metals and, when a corrosion inhibitor is added to slurries, the erosive wear rates of metals reduces significantly. Two types of micro-mechanism were deduced from the observation of eroded surfaces by SEM: (1) local exfoliation, and (2) micro-cutting. The corrosion inhibitor can alter the micro-mechanism from local exfoliation to micro-cutting. The analyses show that the erosive wear of selected metals in slurries results from the synergistic effects of wear by solid particles plus fluid corrosion.     

Influence of microstructure on erosion resistance of steels

Erosive wear due to solid particle impingement is a very intensive degradation process of surface layers of metallic materials. Erosion resistance is influenced by the working conditions (impact angle, impact velocity of solid particles, size, shape, hardness and amount of impinging particles) and the parameters of the worn material like hardness and microstructure. In our experiments some structural and tool steels were tested by slurry with SiO₂ particles at a flow velocity of 20 m/s. The microstructures of the tested steels were modified in a broad range by changing the conditions of their heat treatment. Increasing pearlite share in the structure of annealed carbon and low-alloyed steels has a positive effect on their erosion resistance. The growing carbon content in the tested hardened steels increases their erosion resistance. Maximum erosion resistance was found in hardened chromium ledeburite steel. Hardened high-speed steel HS 11-0-4 in spite of its high hardness has lower erosion resistance than ledeburitic chomium steels. An increasing amount of retained austenite and decreasing carbide and martensite shares with growing quenching temperature of the tested ledeburitic chromium steels leads to the reduction of their erosion resistance.     

Wear behaviour of some low alloyed steels under combined impact/abrasion contact conditions

The wear behaviour of some low alloyed steels has been investigated using a laboratory impeller–tumbler wear test equipment in which the steel samples are worn by angular granite particles under combined impact/abrasion wear contact conditions. The wear of the steels was evaluated by weight loss of the steel samples while the wear mechanisms of the steels were investigated by post-test light optical microscopy (LOM), scanning electron microscopy and energy dispersive X-ray analysis. The worn steel surfaces display a very rough surface topography with pronounced craters and distinct grooves caused by high and low angle impacts, i.e. abrasive wear, respectively. Besides, fragments of embedded granite particles are frequently observed in the worn surface of the steels. The wear of the steels tends to decrease with increasing steel hardness. However, instead of using the bulk hardness value the hardness of the worn/plastically deformed surface layer should be used when modelling the wear resistance. Further, the wear resistance of the steels was found to be dependent on the microstructure and chemical composition. Steels with similar type of microstructure show a linear decrease in weight loss with decreasing grain size and increasing carbon content.     

马氏体球墨铸铁腐蚀磨损特性研究

对马氏体球墨铸铁在不同pH值石英砂浆中的静载三体腐蚀磨损特性进行了试验研究,并与铬白口铸铁进行了对比。结果表明：无论在静栽三体磨料磨损或静载三体腐蚀磨损中,马氏体球置铸铁均优于低铬白口铸铁。适当提高含硅量,有利于提高腐蚀耐磨损性,而且在酸性砂浆中效果较明显。     

Wear behavior of bainitic steels

A systematic study of the wear properties of a series of 0.5 wt.% Mo, 0.003 wt.% B bainitic steels has been made under dry sliding conditions. In contrast to most of the established wear models and experimental data, it was found that, for eight of the nine materials, the wear rate is not a linear function of load.The wear rate data have been analyzed with respect to chemical composition, hardness, monotonic-cyclic stress strain parameters, fatigue properties, Charpy impact data and microstructure. It is shown that the chromium content has the most significant influence on wear rate. Since these bainitic steels have inherently high impact resistance, which is improved with chromium additions, it is possible to achieve an attractive combination of properties with a steel containing 0.2 wt.% C, 2.0 wt.% Cr and 1.5 wt.% Mn.The wear resistance of the bainitic steels is compared with previous work on pearlitic steels tested under the same conditions. While the best pearlitic steels stand apart, it is seen that the best bainitic steel tested to date is better than some fully eutectoid steels containing 0.7 wt.% C.     

Wear behaviour of forging steels with different microstructure during dry sliding

Sliding wear behaviour of two types medium carbon microalloyed steels containing various microstructures was investigated on a 320 mesh SiC paper at a sliding speed of 0.33 m/s with a load of 6 N and sliding duration of 4 min under dry sliding conditions (the sliding distance, 80 m). The experimental results showed that the different microstructures cause a great influence on the wear resistance performance of the steels. Water quenched samples with martensite structure have the highest hardness and wear resistance performance. That is because, water cooled samples contained higher amount of carbon in the solid solution. On the other hand, air or sand cooling from forging temperature results in a decrement of hardness and wear resistance in steel-1 and steel-2. However, air cooled samples showed slightly higher wear resistance than sand cooled samples due to finer grain sizes and the larger pearlite and/or precipitation contributions.     

Assessment of the erosion resistance of steels used for slurry handling and transport in mineral processing applications

The wear environment of steels used for containing, transporting and processing erosive mineral slurries is often such that fluid borne particles form a layer moving at high speed across the wearing surface. Information on the performance ranking of such materials is limited, particularly with respect to the influence of steel hardness and microstructure on the resistance to erosion. This is particularly important for the oil sands industry of Northern Alberta where handling and processing of essentially silica-based solids results in extremely severe wear conditions. This paper presents slurry erosion data obtained on 11 commercially available wear resistant plate and pipeline steels with hardness values up to 750 HV. These data were obtained using a Coriolis erosion tester operated at 5000 rpm with an aqueous slurry containing 10 wt.% of 200–300 μm silica sand particles.

The Coriolis erosion tester was selected because it provides a low-angle scouring action that simulates the erosive conditions encountered in oil sands and tailings pipeline transport and in some related processing operations. Results show that this test method is able to discriminate clearly between the erosion resistance of these steels, expressed in terms of specific energy (the energy necessary to remove unit volume of test material), with the most erosion resistant steel being more than five times superior to the least resistant. A graphical relation between steel hardness and erosion resistance is given. A comparison is also made between slurry erosion data and the performance of the materials in the ASTM G65 dry sand rubber wheel (DSRW) sliding abrasion test. Comments on the influence of the macro- and microstructures of the steels on their wear behaviour are included.     

Erosion–corrosion assessment of materials for use in the resources industry

The erosion–corrosion properties of a range of ferrous-based materials that are currently being used or have potential for use in the resources industry have been assessed using a slurry pot erosion–corrosion (SPEC) test rig that has the capability of establishing the separate components of erosion, corrosion and synergy.Testing was performed, at 30 °C, in an aqueous slurry containing 35 wt% AFS 50–70 silica sand and a 3.5 wt% NaCl solution. Erosive action was supplied through high-speed rotation of a rubber-lined impeller.Erosion–corrosion performance of materials evaluated was related to composition/microstructure and hardness. Test data correlated with available service experience.The results showed that the cast Cr white irons with (i) a structure that was essentially a duplex stainless steel containing a distribution of hard carbides and (ii) a near eutectic Cr white iron exhibited the highest erosion–corrosion resistance of the materials tested. The evaluation of the Cr white irons also highlighted the influence of Cr and C levels on the E–C properties of these materials.E–C assessment of selected carbon steels confirmed that the erosion-only rates and synergistic levels showed a general decline with increasing carbon content and hardness. As expected, a low C steel pipe product displayed very mediocre erosion–corrosion behaviour as a consequence of its very low intrinsic corrosion resistance and inferior wear properties. This reflected service experience, however, such products are still being used, due to the comparatively low initial cost.A TiC particle-reinforced AISI 316 stainless steel exhibited an almost 45% improvement in the E–C resistance, when compared with an AISI 316L stainless steel.     

The abrasion endurance of hard weld deposits from chromium-manganese electrodes

The wear behaviour of hardfacing alloys obtained with five types of coated electrodes with various contents of chromium (1.6 to 12.5%) and manganese (0.8 to 1.8%), is presented. Relative abrasive endurance compared with carbon steel was determined by abrasive wear tests using a rotating disc machine. The highest relative endurance was obtained with a weld deposit with 1% manganese and 2.2% chromium, and a coarse grained austenite-martensite structure. Fully martensitic structures of higher hardness were inferior. The wear behaviour of hardfacing alloys depends upon both the structural components and the grain size shown by means of abrasive wear tests in laboratories or exploitation endurance tests. Abrasive wear testing can assess wear resistance and be a guide to service performance.     

Friction and Wear of Metals in Gases Up to 600 C

Apparatus is described for measuring friction and wear in controlled atmospheres. A comparison is made of the room temperature behavior of copper, mild steel and brass, rubbed against a hardened tool steel, in four environments—vacuum (10^?3 mm Hg), dry helium, dry carbon dioxide, and dry air. The effect of varying the water vapor content in air is also discussed.

The initial selection of rubbing pairs for service at elevated temperatures is gaseous environments under unlubricated conditions, is based on their long-term resistance to corrosion and their ability to give low wear rates. In general, therefore, the materials must be hard. Several alloys having chromium contents of between 1% and 30%, and hardness values in the range 200–1000 vpn have been investigated. These included two low-chromium nitrided steels, a tungsten-chromium tool steel and a series of four Co-Cr-W alloys. Specific wear rates and friction coefficients varied markedly with temperature, and values in the ranges 10^?13–10^?8 cm³/cm kg and 0.1–0.8, respectively, were obtained in both dry carbon dioxide and dry helium. Lowest wear rates were observed with the nitrided steels. The diverse characteristics observed are discussed on the basis of current theories of adhesive wear.     

Ductility and the abrasive wear resistance of hot work die steels

Two-body abrasive resistance has been determined as a function of tempering temperature for a conventional hot work die steel and two experimental hot work die steels. After tempering in the secondary hardening range both experimental steels exhibit abrasive wear resistance comparable with or superior to that of the conventional die steel. In addition, the abrasive wear behavior of the three steels has been assessed using an approach suggested by one of the authors which emphasizes the role of ductility in determining abrasive wear resistance. As suggested by that approach, the product of the wear ratio and the bulk hardness tends to decrease with increasing tensile strain to fracture.     

新型车轮材料的磨损特性试验研究

采用JD-1型轮轨试验机对四种新型车轮材料做材料摩擦磨损特性试验研究,采用JA4103型电子称重仪对磨损后的试件进行磨损量测量,利用JB-6C轮廓仪对磨损后的轮廓进行分析。试验结果表明,在相同实验条件下,材料的磨损量随着含碳量的增加而减少,含碳量越高,耐磨性越强。磨损后磨痕粗糙度明显增加,磨痕的粗糙度与材料的含碳量、硬度等都没有明显的关系,并且本试验得到的磨痕粗糙度Ra为0.4μm左右。材料的耐锈蚀性与材料中的含铬量有着直接的关系,铬元素的抗锈蚀能力明显。     

Friction and Wear Behavior of Austenitic Stainless Steel: Influence of Atmospheric Humidity,Load Range,and Grain Size

Research conducted on steels is motivated by a technological need to further improve their properties. Among the different steel types, austenitic stainless steels possess good corrosion resistance and formability. However, they also have a relatively low yield strength. One way of increasing the yield strength is by grain refining. This work presents a study on the effect of relative humidity and applied load range on the friction and wear of AISI 304 austenitic stainless steel characterized by two different grain sizes: 2.5 and 40 m. Using a precision microtribometer, with applied loads in the N regime, it was found that capillarity plays a dominant role. At the same loads, in high humidity environments, both the fine and coarse grain steels exhibit high friction relative to measurements performed under dry conditions. At loads greater than 2 mN a reversal in microfrictional behavior occurs in that microfriction was greater under dry conditions than under moist conditions. At loads of 2 N, using a standard ball-on-disk tribometer, severe wear was evident at low humidities while relatively lower wear was observed at high humidities indicating a lubricating effect of water.     

三元硼化物基金属陶瓷覆层性能的研究

以钼粉、铁-硼合金粉和铁粉为原料，加入料浆添加剂，制备出成形料浆；用料浆喷涂法在Q235钢基体上成形覆层坯体；在真空烧结炉中通过原位反应液相烧结工艺制备出三元硼化物基金属陶瓷覆层。覆层强化了钢基体的力学性能，覆层与钢基体产生牢固的冶金结合，并具有较高的硬度和优良的耐磨性、耐腐蚀性，在机械工程领域具有广泛的应用前景。     

GCr15及G20CrNi2Mo轴承钢高温润滑条件下摩擦磨损性能

为了探究轴承钢在高温润滑条件下的摩擦磨损性能,采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、洛氏硬度计等对GCr15高碳轴承钢和G20CrNi2Mo渗碳轴承钢组织、物相及硬度进行了表征,利用QG-700型气氛高温摩擦磨损试验机研究轴承钢材料不同条件下的高温润滑摩擦磨损性能,并分析其磨损机制.结果表明:2种轴承钢...     

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.     

35CrMo钢表面铁基激光熔覆层的组织和耐磨性能

采用CO2激光熔覆装置将LC3530铁基粉熔覆在35CrMo钢基体表面,研究了熔覆层的显微组织、硬度和耐磨性能,并与基体的进行对比。结果表明:基体组织为回火索氏体,晶粒尺寸在20μm左右,而熔覆层的组织为均匀细小的等轴晶,晶粒尺寸大多在8μm;基体的平均硬度为254.1HV,而熔覆层的平均硬度为640.5HV,且硬度分布更加均匀;在相同试验条件下,熔覆层试样的磨损量仅为基体试样的1/7,磨损系数是基体试样的1/5,且磨损后熔覆层试样的表面粗糙度较磨损前的大幅下降,表明激光熔覆后35CrMo钢的耐磨性能得到显著提高;基体试样的磨损机制为犁削磨损,而熔覆层试样的磨损机制为微观切削,其优异的耐磨性能与含有铁、铬、钼和碳等元素的高硬度合金碳化物的形成有关。     

Influence of heat and thermochemical treatment on abrasion resistance of structural and tool steels

Abrasive wear is responsible for intensive degradation of machine parts or tools. This process starts as an interaction between hard, mostly mineral, particles and the working surface. Methods of increasing the lifetime are based on application of abrasion resistant materials or creation of hard, wear-resistant surface layers or coatings on the surfaces of machine parts or tools. Carbon and low-alloy steels with different types of thermochemical treatment (case hardening, nitriding) are used in cases of low abrasion. Another method of increasing lifetime is the application of ledeburitic steels. The wear resistance of these steels depends on their chemical composition and heat treatment. The results of laboratory tests of thermochemically treated steels, heat-treated ledeburitic chromium steels and high-speed steels show the effect of the microstructure of these steels on their abrasion resistance. Abrasion resistance of carburized low-alloy steels is on the same level as in high-carbon structural and tool steels. In ledeburitic chromium steel maximum abrasion resistance was achieved by quenching from 1100 °C whilst in ledeburitic chromium–vanadium steel the optimum quenching temperature was 1150 °C. Growing abrasion resistance was caused by increasing amounts of retained austenite.     

The slurry erosive wear of physically vapour deposited TiN and CrN coatings under controlled corrosion

The erosion-corrosion of mild steel (BS6323), in the presence and absence of physically vapour deposited (PVD) TiN and CrN coatings, was studied, in comparison with that of AISI 304 stainless steel, in an aqueous alkaline slurry solution containing alumina particles. The influence of applied potential and particle velocity on the total erosion-corrosion loss was examined, and the respective corrosion and erosion damage (both contributing to the overall weight loss) then assessed by means of microscopical investigation of the morphology of the damaged surface, and subsequently evaluated quantitatively. The superior erosion-corrosion resistance of both the coatings compared to that of the uncoated mild and stainless steels was shown to be due to their resistance to both wear and corrosion. According to the detailed corrosion mechanisms revealed and different responses to wear, schematic diagrams were proposed to outline the main features of the corrosion-erosion process and the individual roles of erosion and corrosion. Discrete differences, in terms of the respective erosion and corrosion processes, between the TiN and CrN coatings, and between the mild and stainless steels, were also investigated and discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparison of wear properties of tool steels AISI D2 and O1 with the same hardness

Two commercial cold work tool steels, AISI D2 and O1, were heat treated in order to obtain the same hardness 700 HV (60 HRc) and were subsequently tested in three different modes of wear, namely in adhesion, three-body and two-body abrasion, by using pin-on-disk, dry sand/rubber wheel apparatus and pin abrasion on SiC, respectively. Even though AISI O1 and D2 steel are heat treated to the same hardness, they perform differently under the three modes of wear examined. The results show that the steel microstructures play the most important role in determining the wear properties. For relatively low sliding speeds AISI O1 steel performs up to 12 times better than AISI D2 steel in adhesive wear. For higher sliding speeds, however, this order is reversed due to oxidation taking place on the surface of the AISI D2 steel. The wear rate of both tool steels in three-body and two-body abrasion wear is proportional to the applied load. In three-body abrasive wear, AISI D2 exhibits a normalised wear rate about two times lower than the AISI O1 tool steel, and this is due to the presence of the plate-like hard carbides in its microstructure. Both tool steels perform 3–8 times better in three-body abrasive wear conditions than in two-body abrasive wear.