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.     

Abrasive wear behavior of different case depth gas carburized AISI 8620 gear steel

In this study, abrasive wear behaviors of gas carburized AISI 8620 steels with different case depths were examined. AISI 8620 steels yield excellent carburizing results and are used in manufacturing of gears. Two carburized and quenched specimens with different case depths were produced. Specimens were prepared at HEMA Gear Factory. Wear tests were carried out using pin-on disc test machine. Specimens were abraded under 10, 25 and 40 N loads by using 80 grid Al₂O₃ and SiC abrasive papers. Mass losses were measured using an electronic balance with accuracy of 10⁻⁴ g. Results of this study reveal that data on laboratory samples can be used to interpret the abrasive wear performance of AISI 8620 gas carburized steel gears. It has been observed that gas carburizing time affects the case depth, and in turn, specimen with higher case depth has shown better wear resistance. In addition to this, as the case depth has increased, the hardness of the material has increased as well.     

Strain Hardening: Can it Affect Abrasion Resistance?

It has been largely reported in the literature that previous strain hardening has none or negligible effect on abrasive wear resistance. Those results are mainly obtained using sand rubber wheel tests and pin-on-disk tests, and have been attributed to the large strain hardening promoted by the abrasion phenomena themselves. The stresses involved in those tests are very high and the stress distributions spread toward subsurface regions at large depths. This work investigates the effects of strain hardening on low-severity (low stress at low depth) abrasive wear resistance. Microabrasion tests, normally regarded as lower stress tests, were used in order to impose low severity. Two types of stainless steels were tested: an austenitic AISI 304 steel and a ferritic AISI 430 steel. Strain hardening was obtained via thickness reduction (20%) of stainless steel sheets in a laboratory cold rolling mill. The microabrasion wear tests were carried out in a fixed-ball microabrasion tester with a three-axis load cell to continuously and simultaneously monitor the forces involved in the tests. Contrary to many findings so far in the literature, previous strain hardening increased abrasion wear resistance (55 and 63%, respectively) for both materials. Hertz calculations, simulations using Finite Element Program with explicit solution, conventional mechanical tests, microhardness profiles, microstructural analysis, and X-ray diffraction analysis were used to explain this paradigm shift for the case of microabrasion tests.     

Abrasive wear behavior of boronized AISI 8620 steel

In this study, AISI 8620 steel was boronized using the solid state boronizing technique. Processes were carried out at the temperatures of 850, 900 and 950 °C for 2, 4 and 6 h of treatment. Abrasive wear behavior of the samples boronized at different temperatures and treatment durations have been examined. Using boronized and unboronized samples, abrasive tests were conducted using pin on disc test apparatus. 80 and 120 mesh aluminum oxide (Al₂O₃) abrasive papers were used in the abrasion experiments and the samples were subjected to abrasion under 10, 20 and 30 N loads. Boronized steels exhibited an improvement in abrasive wear resistance reaching up to 500%. Microstructures and wear surfaces of the samples were inspected using SEM microscopy. SEM examinations revealed that the thickness of the boride layer on the steel surfaces changes with changing process durations and temperatures. The presence of boride formed in the borided layer at the surface of the steels were determined by XRD analysis and microhardness values of the iron borides (FeB, Fe₂B) formed on the steel surface were found to be over 1600 HV.     

An evaluation of the wear behaviour of a dual-phase low-carbon steel

Wear behaviour of dual-phase AISI 1020 steel was investigated. The steel was austenitized at critical transformation temperature and rapidly quenched. Thus, the structure of the steel consists of martensite and ferrite phases in different proportions. Heat treated samples were subjected to wear with a cylinder-on-cylinder sample configuration under dry sliding conditions. Wear resistance was determined as functions of hardness and proportion of martensite phase, and elongation of the steel. The wear resistance of the dual-phase 1020 steel was also compared with those of hardened and tempered AISI 1040 and 8640 steels. It was indicated that the wear resistance of the test steel decreases with martensite proportions, and increases with martensite hardness and elongation of the steel.     

Comparative Study of Thermally Sprayed Coatings Under Different Types of Wear Conditions for Hard Chromium Replacement

The tribological properties of part surfaces, namely their wear resistance and friction properties, are decisive in many cases for their proper function. To improve surface properties, it is possible to create hard, wear-resistant coatings by thermal spray technologies. With these versatile coating preparation technologies, part lifetime, reliability, and safety can be improved. In this study, the tribological properties of the HVOF-sprayed coatings WC–17%Co, WC–10%Co4%Cr, WC–15% NiMoCrFeCo, Cr₃C₂–25%NiCr, (Ti,Mo)(C,N)–37%NiCo, NiCrSiB, and AISI 316L and the plasma-sprayed Cr₂O₃ coating were compared with the properties of electrolytic hard chrome and surface-hardened steel. Four different wear behavior tests were performed; the abrasive wear performance of the coatings was assessed using a dry sand/rubber wheel test according to ASTM G-65 and a wet slurry abrasion test according to ASTM G-75, the sliding wear behavior was evaluated by pin-on-disk testing according to ASTM G-99, and the erosion wear resistance was measured for three impact angles. In all tests, the HVOF-sprayed hardmetal coatings exhibited superior properties and can be recommended as a replacement for traditional surface treatments. Due to its tendency to exhibit brittle cracking, the plasma-sprayed ceramic coating Cr₂O₃ can only be recommended for purely abrasive wear conditions. The tested HVOF-sprayed metallic coatings, NiCrSiB and AISI 316L, did not have sufficient wear resistance compared with that of traditional surface treatment and should not be used under more demanding conditions. Based on the obtained data, the application possibilities and limitations of the reported coatings were determined.     

Wear Behavior of Ceramic Powder and Solid Lubricant Cladding on Carbon Steel Surface

Thick composite coatings of carbides on a metal matrix are ideal for use in components that are subjected to severe abrasive wear. It is a metal matrix composite (MMC) that is reinforced by an appropriate ceramic phase, a solid lubricant coating to reduce friction and to protect the opposing surface. This study tested the wear behavior of a carbon steel surface after cladding by a gas tungsten arc welding (GTAW) method to enhance wear resistance. The microstructures, chemical compositions, and wear characteristics of the cladded surfaces were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The coating was uniform, continuous, and almost defect-free, and particles were evenly distributed throughout the cladding layer. The results of wear tests indicate that the friction coefficient of the TiC coating is lower than that of AISI 1020 carbon steel. Thus, the wear depth of the TiC coating is only one tenth of that exhibited by the AISI 1020 carbon steel. The experiments confirm that the cladding surfaces of TiC particles reduce the wear rate and friction.     

A comparative study of the wear behaviour of sintered and laser surface melted AISI M42 high speed steel diluted with iron

Powders of AISI M42 high-speed steel (HSS) were blended with different proportions of water-atomised iron powders. The powders were subsequently submitted to uniaxial pressing and then divided in three lots. The first was submitted to sintering, the second was submitted to sintering plus laser surface melting (LSM) and the third was submitted to sintering plus LSM plus double tempering at the secondary hardening peak temperature of M42 HSS. The objective of this procedure was to evaluate the processing route that leads to reduced porosity in AISI M42 HSS and to higher abrasive wear resistance. Therefore the samples, with different chemical compositions and microstructures, were submitted to a detailed microstructural characterisation followed by microscale hardness and abrasive wear tests. It was observed that LSM leads to almost complete elimination of residual porosity and to the dissolution of large brittle carbides that are present in the as-sintered samples, leading to a homogeneous and extremely fine microstructure. This microstructure is formed of saturated plate martensite and a small proportion of retained austenite. The double tempering treatment, carried out in the laser surface melted samples samples, leads to the elimination of retained austenite and to a decrease of the lattice parameters of martensite due to the precipitation of thin carbides within martensite. As a result, while the hardness of the material in the sintered condition is between 245 and 625 HV (depending on the proportion of dilution with iron), after LSM the hardness is higher than 820 HV in all the samples. Surprisingly, the abrasive wear resistance of the laser melted and of the laser melted and tempered samples is lower than that of the as-sintered ones. Observation of the wear craters by scanning electron microscopy shows that this result is due to the different wear mechanisms acting on the samples processed by different routes.     

Abrasive wear resistance of some commercial abrasion resistant steels evaluated by laboratory test methods

The aim of the present study is to evaluate the abrasive wear resistance of some potential abrasion resistant steels exposed to different types of abrasive wear contact conditions typical of mining and transportation applications. The steels investigated, include a ferritic stainless steel, a medium alloyed ferritic carbon steel and a medium alloyed martensitic carbon steel.The abrasive wear resistance of the steels was evaluated using two different laboratory test methods, i.e. pin-on-disc testing and paddle wear testing that expose the materials to sliding abrasion and impact abrasion, respectively. All tests were performed under dry conditions in air at room temperature. In order to evaluate the tribological response of the different steels post-test characterization of the worn surfaces were performed using optical surface profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. Besides, characterization of the wear induced sub-surface microstructure was performed using optical microscopy.The results show that depending on the abrasive conditions a combination of high hardness and toughness (fracture strain) is of importance in order to obtain a high wear resistance. In the pin-on-disc test (i.e. in sliding abrasion) these properties seem to be controlled by the as-rolled microstructure of the steels although a thin triboinduced sub-surface layer (5–10 μm in thickness) may influence the results. In contrast, in the paddle wear test (i.e. in impact abrasion), resulting in higher forces acting perpendicular to the surface by impacting stones, these properties are definitely controlled by the properties of the active sub-surface layer which also contains small imbedded stone fragments.     

Effect of densification and TiB2 reinforcement on the wear of molybdenum disilicide

Wear tests were done in a pin‐on‐disc machine by sliding MoSi₂ pins against hard‐steel discs in a normal load range of 5–140 N and a speed of 0.5 m/s under nominally dry conditions in the ambient. The specific wear rate of the pin undergoes two transitions: severe to mild at low load and mild to severe at high load. The mild‐wear domain is distinguished by the formation of a protective mechanically mixed layer of steel and its oxides, transferred from the counterface in particulate form. Increasing the hardness by densification and TiB₂ reinforcement lowers the specific wear rate and expands the mild‐wear load domain. However, even when the volume wear rate is normalised with respect to the real contact area (load/hardness) the non‐dimensional wear factor is still seen to decrease with densification and reinforcement. This indicates that fracture toughness may also play an important role in determining the wear‐resistance of these materials. The surface coverage on the pin by the mechanically mixed layer increases with densification and reinforcement. This revised version was published online in July 2006 with corrections to the Cover Date.     

Some observations on two-body abrasive wear

Pin-on-disc-type two-body abrasion tests were carried out on five metals with seven particle sizes over a range of loads, lengths of travel and sliding speeds. The familiar results that two-body abrasive wear is proportional to load and to distance travelled were confirmed. The “size effect”, in which particles below about 100 μm produce progressively less wear, was shown to be independent of load, sliding speed and prior cold working. Increasing the sliding speed from 1 to about 100 mm s^?1 produced an increase in wear resistance of about 50% for AISI 1020 steel. An increase in velocity above 100 mm s^?1 had little effect on the wear resistance. Plots of the wear resistance against the hardness of the annealed metal showed significant deviations from the linear relationship reported in the literature. The result is influenced by both sliding velocity and particle size.     

Wear behaviour of AISI D3 and AISI M3:2 tool steels in a mass production shearing operation

The wear of two tool steels (AISI D3 and AISI M3:2) was compared in a normal production shearing operation by scanning electron microscopy at fixed production intervals.After the wear-in period, in which plastic deformation was observed, abrasive wear occurred by the action of small carbides. Wear was more uniform with AISI M3:2 tool steel than with AISI D3 tool steel and the AISI M3:2 tool produced a better finish of the sheared sheet lips.     

A Pin-on-Disc Study on the Wear Behaviour of Two High-Performance Railway Wheel Steels

The wear behaviour of two railway wheel steels, ER8 and SUPERLOS^®, was studied through pin-on-disc tests, and the results were correlated with those previously obtained with twin-disc tests. The work-hardening of the steels was investigated with Vickers hardness measurements, and the wear mechanisms were studied using scanning electron microscopy. ER8 discs showed higher wear resistance, lower work-hardening ability and less wear damage than SUPERLOS^® ones, confirming the results of the twin-disc tests. Therefore, sliding pin-on-disc experiments are recommended as a simple laboratory technique that can be used as a screening method for wheel steel performance prior to more complex and more expensive tests. The damage in both steels was due to the concomitance of oxidative wear, abrasive wear and fatigue wear. Iron oxide formation protects the steels from severe wear, whereas its detachment causes abrasive wear; furthermore, surface fatigue cracks initiate and propagate leading to the detachment of material flakes.     

Abrasive wear in ceramic laminated composites

Laminated ceramic structures in the system Al₂O₃/Al₂O₃ + 3Y-TZP (A/AZ) were prepared using a tape casting technique in order to obtain ceramic layers with different compositions and thicknesses. Piezo-spectroscopy was used to evaluate the residual stresses arisen from a calibrated mismatch in thermal expansion coefficients of the layers during the sintering process of the composite. The dependence of the residual stresses in the A and AZ layers on their thickness ratio was established. A microscale ball cratering method was used to investigate the influence that the surface compressive stress can play on the abrasive wear resistance of the composite structures. The results were compared with those obtained with an unstressed reference material prepared either by lamination of pure alumina green-sheets or by cold isostatic pressing of alumina powder. The experimental results have shown that the abrasive wear resistance is higher for samples with compressive residual stresses within the surface regions.     

Friction and wear behaviour of sintered steels submitted to sliding and abrasion tests

Fe–C–Mo and Fe–C–Cr steels were sintered by PM processes carried out using different values of temperature and pressure, leading to different microstructures and density values. Flat specimens were submitted to tribological tests in order to evaluate their behaviour under both dry sliding and abrasive wear conditions. A flat-on-cylinder tribometer was used for the sliding tests, while a micro-scale ball cratering device was used for the abrasion tests. The dry sliding wear resistance of the PM steels was mainly influenced by the composition and sintering conditions. In this regard, the best behavior was observed for the more hardenable Fe–C–Mo steels with higher Mo content, sintered under conditions giving rise to bainitic microstructures. A determining role was also played by the porosity content and pore shape: reduction in porosity (obtained by increasing the sintering temperature and the compacting pressure), as well as an increase in pore roundness, led to a significant improvement in the resistance to sliding wear. A mild oxidative wear regime were observed for all the sintered steels under relatively low values of the applied load, while an increase of the applied load led to a delamination wear regime. The resistance to abrasive wear was low for all the tested steels, irrespective of composition and sintering cycle.     

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.     

H13钢激光相变硬化的组织与性能试验研究

为提高H13热锻模具的耐磨性能和耐腐蚀性能,利用激光相变硬化技术对H13钢进行处理,采用XRD衍射仪、光学显微镜、扫描电镜、显微硬度仪、电化学工作站及高温摩擦磨损试验机对其相结构、显微硬度、耐腐蚀性及耐高温磨损性能进行测试。硬化层由针状马氏体、板条马氏体和碳化物组成,硬化深度为0.71 mm,显微硬度约为750 HV0.3。在脱模剂溶液中,硬化层的自腐蚀电流密度比基材小一个数量级。硬化层高温磨损的质量为基材的7%,磨损机理以黏着磨损为主,同时伴有磨粒磨损和氧化磨损。     

Wear of metals at high sliding speeds

High speed sliding wear of AISI 1020 steel, AISI 304 stainless steel and commercially pure titanium (75A) was studied using a pin-on-ring geometry. All the tests were carried out in air without any lubricant. The sliding speed was 0.5–10.0 m s^?1 and the normal force was 49.0 N (5 kgf).The friction coefficient of all the materials tested decreased with the sliding speed; this appears to be a consequence of oxide formation. The wear rate of 304 stainless steel increased monotonically with speed, whereas the wear rate of 1020 steel and titanium first decreased and then increased and again decreased, with a maximum occurring at about 5 m s^?1. The complex variation of the wear rate as a function of speed is explained in terms of the dependence of the friction coefficient, hardness and toughness of the materials on temperature. Microscope examinations of the wear track, the sub-surface of worn specimens and the wear particles indicate that the wear mode was predominantly by subsurface deformation, crack nucleation and growth processes, i.e. the delamination process, similar to the low speed sliding wear of metals. Oxidative and adhesion theories proposed in the past to explain the high speed sliding wear of metals are found to be incompatible with the experimental observations.     

Friction and rolling–sliding wear of DC-pulsed plasma nitrided AISI 410 martensitic stainless steel

In the present work, industrial-scale DC-pulsed plasma nitriding for 20 h at 673 K was used to improve the wear resistance of an AISI 410 martensitic stainless steel. The tribological behaviour was studied and compared to the behaviour of the same steel in as-received condition.Pin-on-disc dry tests, using an alumina ball as counter-body, were carried out to determine the evolution of the friction coefficient. The wear resistance was investigated using an Amsler-disc-machine, employing a dry combined contact of rolling–sliding with three different applied loads. The wear mechanisms involved during rolling–sliding of unnitrided and plasma nitrided steels were investigated by microscopic observation of the surfaces, the corresponding cross-sections and the produced wear debris.The combination of different wear mechanisms taking place in the wear process of unnitrided and nitrided materials were discussed and analyzed. In contrast to the unnitrided steel, DC-pulsed plasma nitrided samples presented an improvement in the friction coefficient and the wear rate.     

Influence of the normal force,abrasive slurry concentration and abrasive wear modes on the coefficient of friction in ball-cratering wear tests

The purpose of this work is to study the influence of the normal force (N), abrasive slurry concentration (C) and abrasive wear modes on the coefficient of friction in ball-cratering wear tests. Experiments were conducted with balls of AISI 52100 steel, an AISI H10 tool-steel specimen and abrasive slurries prepared with black silicon carbide (SiC) particles+distilled water. The tangential (T) and normal loads were monitored throughout the tests and the results have shown that: (i) the coefficient of friction behavior was independent of the normal force and (ii) both the concentrations of abrasive slurries and the subsequent action of the abrasive wear modes, generally, did not affect the behavior or magnitude of the coefficient of friction.