Influence of sliding frequency on reciprocating wear of mold steel with different microstructures

The wear resistance of a low alloy plastic mold steel has been studied under pin-on-flat reciprocating configuration against AISI 52100 steel pins, under variable sliding frequency. The as-received material (HTO; 33 HRC) was heat treated under variable conditions to obtain different microstructures and hardness (HT1, quenched 880 °C, 58 HRC; HT2, tempered 550 °C, 43.4 HRC; HT3, tempered 300 °C, 52 HRC; HT4, annealed, 26 HRC). Under low sliding frequency (1 Hz), no significant differences in the wear resistance of the different materials are observed. Only at 8 Hz, a relationship between hardness and wear resistance is found. The softer annealed material HT4 shows an increasing wear rate under increasing frequency, while the quenched steel HT1 gives the lowest wear at the highest frequency. Wear mechanisms have been studied from SEM and EDS observations. Only HT4 shows a transition from the abrasive and oxidative wear mechanisms found in all cases to an adhesive wear mechanism under the highest frequency.     

Abrasive wear of high speed steels: Influence of abrasive particles and primary carbides on wear resistance

A ball cratering test has been used to investigate the abrasive wear of high speed steels with different volume fraction and size of primary carbides. Three different abrasives, SiC, Al₂O₃ and ZrO₂ were used. Wear mechanisms were investigated by scanning electron microscopy (SEM). A good correlation between the hardness of the abrasives and the abrasive wear coefficient was found. Higher abrasive wear resistance was determined for steels containing coarser primary carbides compared to those without or with smaller carbides. The most pronounced difference in abrasive wear resistance was found for Al₂O₃ abrasives. This indicates that in ball cratering the abrasive medium has to be chosen properly, i.e. with a hardness adjusted to those of both primary carbides and martensitic matrix, to obtain results suitable to rank high speed steels with respect to abrasion resistance.     

Abrasive wear resistance of spheroidal vanadium carbide cast irons

The effect of the chemical composition and heat treatment on the microstructure and abrasive wear resistance of V-Mn, V-Ni-Cr, and V-Mo spheroidal vanadium carbide cast irons (18–23 vol %) has been studied. The wear resistance has been determined under conditions of wear by abrasives with various hardnesses, i.e., corundum and quartz and compared to that of high-chromium cast iron with 13% Cr. It has been found that the advisability of using high-vanadium cast irons is governed by the hardness of the abrasive. When a hard abrasive, i.e., corundum was used, V-Mo cast iron with the maximum concentration of spheroidal VC carbides, which were uniformly distributed in the martensitic matrix, had the highest wear resistance. When a soft abrasive, i.e., quartz, was applied, high-chromium cast iron with a hardness of 68 HRC, which contained the largest amount of M₇C₃ carbides, was more wear-resistant. In the course of isothermal exposure at 300–1000°C, V-Ni-Cr and V-Mo cast irons with an austenitic structure had high resistance to phase and structural transformations. However, the properties and microstructure of V-Mo cast irons with a martensitic matrix depended strongly on the temperature of exposure during heat treatment.     

Abrasive wear study of white cast iron with different solidification rates

The abrasive wear resistance of white cast iron was studied. The iron was solidified using two solidification rates of 1.5 and 15 °C/s. Mass loss was evaluated with tests of the type pin on abrasive disc using alumina of different sizes. Two matrices were tested: one predominantly austenitic and the other predominantly martensitic, containing M₃C carbides. Samples with cooling rate of 15 °C/s showed higher hardness and more refined microstructure compared with those solidified at 1.5 °C/s. During the test, the movement of successive abrasives gave rise to the strain hardening of the austenite phase, leading to the attainment of similar levels of surface hardness, which explains why the wear rate showed no difference compared to the austenite samples with different solidification rates. For the austenitic matrix the wear rate seems to depend on the hardness of the worn surface and not on the hardness of the material without deformation. The austenitic samples showed cracking and fracture of M₃C carbides. For the predominantly martensitic matrix, the wear rate was higher at the solidification rate of 1.5 °C/s, for grain size of 66 and 93 μm. Higher abrasive sizes were found to produce greater penetration and strain hardening of austenitic matrices. However, martensitic iron produces more microcutting, increasing the wear rate of the material. The analysis of the worn surface by scanning electron microscopy indicated abrasive wear mechanisms such as: microcutting, microfatigue and microploughing. Yet, for the iron of austenitic matrix, the microploughing mechanism was more severe.     

Abrasive wear resistance of textured steel rings

The fundamental aim of the present research is to study the effect of dimple shape and area density on abrasive wear in lubricated sliding. The other aims are to recommend a method of obtaining the local linear wear of a textured ring on the basis of profilometric measurement and to analyse the changes in the surface topography of this ring with selection of parameters that could monitor the “zero-wear” process.The experiments were conducted on a block-on ring tester. The stationary block made from cast iron of 50 HRC hardness was ground. The rotated ground ring was made from 42CrMO4 steel of 32 HRC hardness. The rings were modified by a burnishing technique in order to obtain surfaces with oil pockets. Oil pockets of spherical and of drop shape were tested. The pit-area ratios were in the range: 7.5–20%. The tested assembly was lubricated by oil L-AN 46. Because of the great hardness of the co-acting parts the wear resistance test was carried out under artificially increased dustiness conditions. The dust consists mainly of SiO₂ and Al₂O₃ particles. Measurement of local microscopic ring wear was made using a three-dimensional scanning instrument. The tendencies of ring surface topography changes during wear were analysed. Various methods of obtaining the local wear value during a low wear process were proposed and compared. We found that a spherical shape of dimples was superior to a drop shape with regard to wear resistance of steel rings.     

Tempering temperature effects on abrasive wear of mottled cast iron

The effects of different tempering temperatures (300–600 °C) on abrasive wear resistance of mottled cast iron were studied. Abrasive wear tests were carried out using the rubber-wheel test on quartz sand and the pin test on Al₂O₃ abrasive cloths. The retained austenite content of the matrix was determined by X-ray diffraction. The wear surface of the specimens was examined by scanning electron microscopy for identifying the wear micromechanism. Bulk hardness and matrix hardness before and after the tests were measured. The results showed that in the two-body (pin-on-disc test) system, the main wear mechanism was microcutting and high matrix hardening was presented. The wear rates presented higher correlation with the retained austenite than with the bulk and matrix hardness. In the three-body system (sand–rubber wheel), the wear surfaces presented indentations due to abrasive rolling. The wear rates had better correlation with both the bulk and matrix hardness (before and after the wear test) than with the retained austenite content. There are two groups of results, high and low wear rates corresponding to each tribosystem, two-body abrasive wear and three-body abrasive wear, respectively.     

基体组织对高钒高速钢干滑动摩擦磨损行为的影响

利用销环式滑动磨损试验机测试了具有不同基体组织的高钒高速钢的干摩擦磨损性能，并利用扫描电子显微镜对其失效行为进行了分析。结果表明：以低碳板条马氏体为主要基体组织的高速钢可同时较为有效地抵御显微切削与疲劳磨损，其组织中均匀分布的高硬度VC能够充分发挥抗磨骨架作用，因而具有最优的耐磨性。基体组织为铁素体时，基体无法对VC提供有效的支撑，磨损失效形式为严重的显微切削及表面粘着磨损，耐磨性很差。基体以面碳马氏体为主时,抵抗循环疲劳和热疲劳的能力较差，导致耐磨性下降。     

Influence of abrasive hardness on the wear resistance of high chromium irons

The resistance to abrasive wear was determined for a series of alloyed white cast irons in a high stress abrasion test which utilizes a specimen in sliding contact with bonded abrasives. These were conducted on silicon carbide, alumina and two sizes of garnet abrasive.The results indicate that the hardness, or type, of abrasive used in the test significantly influenced the wear rate of white irons, i.e. the rate of wear increased with increasing hardness of the abrasive. Also, the results indicate that the type of abrasive used in the test was a significant factor in ranking white irons for resistance to high stress abrasion. When tested on silicon carbide or alumina abrasive, as-cast austenitic irons exhibited lower rates of wear than heat treated martensitic irons; when tested on garnet, an abrasive of lower hardness, those irons with martensitic matrix microstructures exhibited the same or less wear than irons with austenitic matrix microstructures. It was also evident that heat treated irons with martensitic matrix microstructures exhibited varying degrees of resistance to abrasive wear depending on cooling rates and alloy content.     

Study on relative wear resistance and wear stability of high-speed steel with high vanadium content

In this work, a new concept of wear stability was put forward by authors, and it was quantitatively expressed by factor of wear stability. Different hardness, impact toughness and retained austenite content high-speed steel with high vanadium content samples were obtained by varying heat treatment conditions. The effects of hardness, impact toughness and retained austenite content on relatively wear resistance and wear stability were studied under abrasive wear condition. Results show that relative wear resistance increases with increasing hardness or decreasing impact toughness, whereas the wear stability rises with the increasing of hardness or impact toughness. The analyzing results reveal that mechanical behaviors are only apparent factors to influence wear behaviors. Relative wear resistance substantially depends on retained austenite content (Ar). At retained austenite content of about 30 vol.%, the relative wear resistance is optimal. However, wear stability is scarcely influenced by retained austenite content, which depends on the maximum changing amount of retained austenite under certain condition (ΔAr) in essence. With increasing ΔAr, wear stability linearly decreases.     

Wear behaviour of Al/(Al2O3p+SiCp) hybrid composites

In this study, dry sliding metal–metal and metal–abrasive wear behaviours of the aluminium matrix hybrid composites produced by pressure infiltration technique were investigated. These composites were reinforced with 37 vol% Al₂O₃ and 25 vol% SiC particles and contained up to 8 wt% Mg in their matrixes. While matrix hardness and compression strength increased, amount of porosity and impact toughness decreased with increasing Mg content of the matrix. Metal–metal and metal–abrasive wear tests revealed that wear resistance of the composites increased with increasing Mg addition. On the other hand, abrasive resistance decreased with increasing test temperature, especially above 200 °C.     

Abrasive wear resistance of starch consolidated and sintered high speed steel

The abrasive wear resistance of starch consolidated (SC) and super solidus liquid phase sintered (SLPS) M3/2 high speed steel (HSS) samples have been evaluated by a two-body micro-abrasion test (low stress abrasion), using 6 μm diamond abrasive particles, and a three-body abrasion test (high stress abrasion), using significantly larger abrasive particles of blast furnace slag (600 HV) and silicon carbide (2400 HV), respectively. In the tests a commercial powder metallurgical (PM) HSS was used as a reference material.The results show that the microstructure of the SC and SLPS HSS samples is strongly dependent on the sintering temperature used. With increasing temperature the microstructure ranges from a porous (5% porosity) relatively fine grained low temperature sintered microstructure to a fully dense relatively coarse grained high temperature sintered microstructure with eutectic carbides/carbide networks. However, despite the pronounced microstructural differences displayed by the as-sintered HSS microstructures these show a relatively high abrasive wear resistance, comparable with that of a HIPed HSS reference, both under low and high stress abrasion contact conditions. The characteristic features of the low and high temperature sintered microstructures, i.e. the pores and coarse eutectic carbides/carbide networks, only show a limited impact on the wear rate and the wear mode (dominant wear mechanism). The results obtained imply that near net shaped components manufactured by starch consolidation and super solidus liquid phase sintering might be of interest in tribological applications.     

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.     

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.     

喷射成形S390高速钢的组织和性能

研究了喷射成形S390高速钢组织和性能,结果表明:喷射成形S390高速钢沉积坯具有低的氧含量,仅为18ppm,组织无宏观偏析,主要有M6C和MC两种碳化物相,碳化物呈均匀弥散分布在晶界和晶内。经过热处理后,喷射成形S390合金的抗弯强度可达4044MPa,合金硬度随淬火温度呈上升趋势,在1250℃淬火后,硬度达到了HRC69.3。     

Wear Mechanisms at High Temperatures. Part 1: Wear Mechanisms of Different Fe-Based Alloys at Elevated Temperatures

To extend the lifetime of the sinter grate used to crush the sinter cake into smaller pieces for steel fabrication, a study was undertaken to investigate which wear processes are primarily responsible for limiting the lifetime of the sinter grate. Several wear processes could be identified. The sinter temperature which is up to 800 °C causes temperature-induced material ageing and oxidation. The falling of the sinter cake onto the sinter grate causes high impacts, erosion and abrasive wear. There is enormous economic pressure, which makes the most cost-efficient solution the most attractive one, not the technically “best” coating material; thus, Fe–Cr–C hardfacing alloys are mostly used. In view of the above, four different alloys which are promising for this application were studied with regard to their wear resistance. Each wear mechanism was investigated in a special test tribometer. Fatigue wear caused by multiple impacts and abrasion was tested in the high-temperature continuous impact abrasion test. Materials behaviour in heavy single impacts was evaluated in the single impact test. Characterisation of microstructure and wear behaviour was performed by optical microscopy and scanning electron microscopy. The results obtained with the help of the different measurement techniques were linked and set into comparison to calculate the volumetric wear of the specimen. Aim of this work was to investigate the influence of the material parameters such as macrohardness, hard phase content, microstructure coarseness on the wear resistance in impact loading and abrasive applications at high temperatures. Results also indicate that the matrix ability to bind carbides at high temperature as well as the matrix hardness at high temperatures strongly influence the wear resistance in the different tests. Those material parameters get correlated to the wear rates in different material demands. The test results indicate that at higher temperatures material fatigue becomes a major wear-determining factor which makes the matrix hardness and the matrix ability to bind carbides at high temperatures very important. Especially, in abrasive wear, a certain content of hard phases is also necessary to keep the wear to a lower level. It could also be shown that in impact loading applications, a coarse microstructure is a disadvantage.     

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...     

Mechanisms of dry wear of some martensitic steels

The basic wear mechanisms operating when two identical steel surfaces are rubbed against each other were studied to determine material parameters essential for wear resistance. Three simple model alloys, with the same basic properties as tool steels, were developed, containing three different predetermined volumes of M₇C₃ carbide, having approximately the same hardnesses after hardening and annealing, and approximately the same composition of the matrix.Unlubricated sliding wear tests were performed in air, using a pin-on-ring type machine. Normal force, sliding speed and sliding distance were varied. Friction force and temperature were recorded during the test and changes in weight of specimens were measured. The worn surfaces were carefully examined by scanning electron microscopy, in an attempt to classify the different wear mechanisms.It was found that corrosive wear dominates at low sliding speeds (2 m/min). Material annealed to a lower hardness had a lower wear resistance, irrespective of carbide content. The wear is characterized as mild.At high sliding speed (100 m/min) and especially for high normal forces, the wear was dominantly by a severe adhesive mechanism. Tempering to a lower hardness gave better wear resistance, which indicates that the room temperature hardness is not significant when a high contact temperature is reached. The influence of the carbide content was complex. The results indicate that a carbide free material is the most wear resistant, because of the more extensive occurrence of corrosive wear. Abrasives such as carbides in the more carbide rich alloys may possibly tear up protective corrosive layers and expose the steel to adhesive wear.     

Experimental investigation of oil pockets effect on abrasive wear resistance

The experiments were carried out using a block-on-ring tester. The stationary blocks were modified by a burnishing technique in order to obtain surfaces with oil pockets of spherical shape. The area density of oil pockets varied in order to explore their effect on wear resistance and wear intensity. Specimen surfaces had dimples with depths 45-60 μm and diameters 1-1.2 mm. The area density of oil pockets S_p was in the range 4-20%. The block samples were made from bronze B101 (CuSn10P) of 138 HB hardness. The rotated rings were made from 42CrMo4 steel, hardness of 40 HRC obtained after heat treatment. The tested assembly was lubricated by mineral oil L-AN 46. The experiment was carried out under artificially increased dustiness conditions. The dust added to oil consists mainly of SiO₂ (74%) and Al₂O₃ (15%) particles. During the test friction force and temperature of block sample were registered. The tendencies of block surface topography changes during wear were analysed. It was found that sliding pairs with textured specimens were not superior to a system with a turned block with regard to abrasive wear resistance.     

Microstructural and abrasive characteristics of high carbon Fe–Cr–C hardfacing alloy

A series of high carbon Fe–Cr–C hardfacing alloys were produced by gas tungsten arc welding (GTAW). Chromium and graphite alloy fillers were used to deposit hardfacing alloys on ASTM A36 steel substrates. Depending on the four different graphite additions in these alloy fillers, this research produced hypereutectic microstructures of Fe–Cr phase and (Cr,Fe)₇C₃ carbides on hard-facing alloys. The microstructural results indicated that primary (Cr,Fe)₇C₃ carbides and eutectic colonies of [Cr–Fe+(Cr,Fe)₇C₃] existed in hardfacing alloys. With increasing the C contents of the hardfacing alloys, the fraction of primary (Cr,Fe)₇C₃ carbides increased and their size decreased. The hardness of hardfacing alloys increased with fraction of primary (Cr.Fe)₇C₃ carbides. Regarding the abrasive characteristics, the wear resistance of hardfacing alloys were related to the fraction of primary (Cr,Fe)₇C₃ carbides. The wear mechanism was also dominated by the fraction of primary (Cr,Fe)₇C₃ carbides. Fewer primary carbides resulted in continuous scratches worn on the surface of hardfacing alloy. In addition, the formation of craters resulted from the fracture of carbides. However, the scratches became discontinuous with increasing fraction of the carbides. More primary carbides can effectively prevent the eutectic colonies from the damage of abrasive particles.     

Gouging and sliding abrasion of austenitic manganese steels reinforced by hard phases

Boron in austenitic manganese steels leads to the formation of (Fe,Mn)₃(B,C) carboborides arranged in a cell-type microstructure.Gouging abrasion tests with a modified 300 J Charpy impact tester (copy of the “Uppsala pendulum”) reveal that these carboborides do not improve the wear resistance. This originates from their relatively low hardness compared with the work-hardened matrix, from a weak bonding to the austenite as well as from favourable conditions for unimpeded crack propagation and crack branching within the carboboride cell walls.However, pin abrasion tests on flint abrasive paper show that carboborides, hardened, for example, by additions of vanadium, substantially increase the abrasive wear resistance. This results from a supporting effect of the hard phase cell structure on the abrasive agent which consequently impedes wear of the softer matrix.