FACTORS INFLUENCING THE WEAR BEHAVIOR OF PM STEELS

1. IntroductionWear is the progressive damage, involving material loss, which occurs on the surface ofa component as a result of its motion relative to the adjacent working parts. The economicconsequences of wear are widespread and pervasive, which involve not only the costs ofreplacement parts but also the expenses involved in machine downtime, lost production,and the consequent loss of business opportunities. A more significant factor is the decreasedefficiency of worn plant and equipment th…     

Microstructure, Mechanical Properties and Wear Behaviourof Deep-Cryogenic-Treated HSS

In this paper we compare the wear behaviour of a vacuum-heat-treated ESR AISI M2 high-speed steel and the same steel that was vacuum heat treated in conjunction with a deep-cryogenic treatment at -196 ~C. Four different tempering temperatures for the specimens austenized at the same austenitizing temperature were carefully selected to obtain various in-advance-determined combinations of the microstructures, the fracture toughness, Kic and the Rockwell-C hardness. Each of the eight specimens was therefore characterised by these microstructures and resulting material properties.The wear study was performed using a reciprocating sliding device under well-controlled contact conditions. Relatively high loads were used to provide enough wear for a comparison of the selected samples. A much harder and dissimilar model counter-material, i.e. silicon nitride ceramic, was used in order to avoid excessive wear of the counter samples and adhesion,which could occur in contacts with similar materials (metals/steels) under such high loads and in non-lubricated conditions.The wear behaviours were then compared and discussed in terms of these microstructures and the related properties. The differences in the wear resistance obtained in our investigation were as high as an order of magnitude. However, the beneficial effects are not a direct result of the type of the treatment, but relate to a proper combination of the resulting fracture toughness and the hardness. The more uniform and moderate values, which, however, tend to be obtained with a deep-cryogenic treatment, are beneficial to the high wear resistance of the selected high-speed steel.     

Fretting wear behavior of liquid nitrided structural steel,En24 and bearing steel,En31

Fretting wear failures are reported in many bearing-shaft assemblies. Fretting wear characteristics of structural steel, En24 in as-received, hardened–tempered and liquid nitrided condition, when fretted with hardened–tempered bearing steel, En31 is reported in this paper. Tests were conducted at different normal loads and at constant slip amplitude under unlubricated conditions. Coefficient of friction under fretting conditions and wear resistance were measured. Surface chemistry influences the fretting wear behavior more than the hardness of the material. The mono phase epsilon iron nitride structure of compound layer formed in liquid nitriding process offers improved fretting wear resistance against bearing steels. The fretting wear resistance also depends upon the normal load and the nature of contact, stick–slip or gross slip.     

Effect of the carbide phase on the tribological properties of high-manganese antiferromagnetic austenitic steels alloyed with vanadium and molybdenum

Effect of special carbides (VC, M ₆C, Mo₂C) on the wear resistance and friction coefficient of austenitic stable (M _s below −196°C) antiferromagnetic (T _N = 40–60°C) steels 80G20F2, 80G20M2, and 80G20F2M2 has been studied. The structure and the effective strength (microhardness H _surf, shear resistance τ) of the surface layer of these steels have been studied using optical and electron microscopy. It has been shown that the presence of coarse particles of primary special carbides in the steels 80G20F2, 80G20M2, and 80G20F2M2 quenched from 1150°C decreases the effective strength and the resistance to adhesive and abrasive wear of these materials. This is caused by the negative effect of carbide particles on the toughness of steels and by a decrease in the carbon content in austenite due to a partial binding of carbon into the above-mentioned carbides. The aging of quenched steels under conditions providing the maximum hardness (650°C for 10 h) exerts a substantial positive effect on the parameters of the effective strength (H _surf, τ) of the surface layer and, correspondingly, on the resistance of steels to various types of wear (abrasive, adhesive, and caused by the boundary friction). The maximum positive effect of aging on the wear resistance is observed upon adhesive wear of the steels under consideration. Upon friction with enhanced sliding velocities (to 4 m/s) under conditions of intense (to 500–600°C) friction-induced heating, the 80G20F2, 80G20M2, and, especially, 80G20F2M2 steels subjected to quenching and aging substantially exceed the 110G13 (Hadfield) steel in their tribological properties. This is due to the presence in these steels of a favorable combination of high effective strength and friction heat resistance of the surface layer, which result from the presence of a large amount of special carbides in these steels and from a high degree of alloying of the matrix of these steels by vanadium and molybdenum. In the process of friction, there are formed nanocrystalline austenitic structures possessing high effective strength and wear resistance on the wear surface of these steels.     

Influence of carbon content on wear resistance and wear mechanism of Mn13Cr2 and Mn18Cr2 cast steels

By means of impact abrasion tests, micro-hardness tests, and worn surface morphology observation via SEM, a comparison research based upon different impact abrasive wear conditions was conducted in this research to study the influence of different carbon contents(1.25 wt.%, 1.35 wt.%, and 1.45 wt.%) on the wear resistance and wear mechanism of water-quenched Mn13Cr2 and Mn18Cr2 cast steels. The research results show that the wear resistance of the Mn18Cr2 cast steel is superior to that of the Mn13Cr2 cast steel under the condition of the same carbon content and different impact abrasive wear conditions because the Mn18Cr2 cast steel possesses higher worn work hardening capacity as well as a more desirable combination of high hardness and impact toughness than that of the Mn13Cr2 cast steel. When a 4.5 J impact abrasive load is applied, the wear mechanism of both steels is that plastic deformation fatigue spalling and micro-cutting coexist, and the former dominates. When the carbon content is increased, the worn work hardening effect becomes increasingly dramatic, while the wear resistance of both steels decreases, which implies that an increase in impact toughness is beneficial to improving the wear resistance under severe impact abrasive wear conditions. Under the condition of a 1.0 J impact abrasive load, the wear mechanism of both steels is that plastic deformation fatigue spalling and micro-cutting coexist, and the latter plays a leading role. The worn work hardening effect and wear resistance intensify when the carbon content is increased, which implies that a higher hardness can be conducive to better wear resistance under low impact abrasive condition.     

Synergistic abrasive—corrosive wear of chromium containing steels

Abstract

Commercial and experimental steels containing various chromium concentrations have been assessedfor their resistance to the combined effects of abrasion and corrosion. The degree of work hardening and macro- and microtoughness of low carbon martensite alloys, dual phase alloys, and metastable austenitic alloys provide good abrasion resistance, while chromium contents > 8% are required. Abrasion and corrosion are synergistic since the kinetics of corrosion are influenced by abrasion. The effects of the frequency of abrasion and corrosion are different for steels of different chromium contents. Low chromium steels perform better under lowfrequency conditions, whereas steels with higher chromium contents resist wear better when there are frequent abrasive periods.     

Effect of the rigidity of the stress state on the wear resistance of materials in hydraulic and impact abrasion wear

In the process of use many parts are subjected to the impact action of abrasive particles contained in a flow (jet) of gas or liquid and ones present on the contacting surfaces in the form of an abrasive layer. Despite the large number of publications devoted to problems of wear of parts, no universal criterion has been developed for evaluating the wear resistance of materials operating under various wear conditions. The present work concerns hydraulic and impact abrasion of various steels and alloys of nonferrous metals. In establishing the dependence of the wear resistance of the studied materials on their properties the authors take into account for the first time the rigidity of the stress state of the worn surface, which allows them to explain the special features of the behavior of the materials when subjected to various kinds of abrasion wear. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 22–30, April, 1997.     

Strength and Wear Behavior of Mg Alloy AE42 Reinforced with Carbon Short Fibers

In addition to the advantage of the lightweight of magnesium alloys, magnesium composites have moderate strength and elastic modulus. The proposed application of magnesium composites as diesel truck pistons makes it necessary to assess their wear performance. Little research data have been discussed on wear behavior of Mg alloy AE42 matrix and its composites. Thus, this paper reports wear behavior of magnesium alloy AE42(Mg–Al–Mn—RE; rare earth) and its composite AE42-C, which contains 23 vol% of randomly oriented carbon short fibers. Materials characterization, including density measurements, hardness testing, microstructures investigation, and compression testing at temperatures of 25, 150,and 300 °C, were conducted. Wear tests were performed under various loads and sliding distances. Wear mechanisms were also proposed based on the examination of worn surfaces using optical microscopy and scanning electron microscopy equipped with EDX(energy-dispersive X-ray spectrometry) analysis system. The hardness of AE42-23 vol% C composite is twice the hardness of the Mg matrix alloy AE42. Significant improvements to yield stress and compressive strength at temperatures of 25, 150, and 300 °C of the composite versus the AE42 alloy are achieved. Wear resistance of the composite is improved considerably versus that of the Mg alloy AE42 at the various sliding distances. Smearing of graphite on the worn surface produces a lubricating film that delays change from mild to severe wear of the composite, especially at high loads. EDX analysis of the worn surface shows oxidation of the matrix alloy at higher wear loads, and this mechanism decreases in the presence of carbon fibers under the same loads. Abrasive wear, oxidation, and plastic deformation are the dominant wear mechanisms for the alloy matrix AE42, whereas mainly abrasive wear is the wear mechanism of AE42-23 vol% C composite under the proposed testing conditions.     

Development of microalloyed high-carbon steels for plough disks

Plough disks are often made of high-carbon steels with small additions of chromium (0.40 to 0.60%), in the as-quenched and tempered condition. As a consequence, they combine wear resistance with the tensile, fatigue, and impact strength necessary to withstand extremely adverse work conditions. In an effort to produce steels for this use with improved mechanical properties, four different steel compositions, all microalloyed with niobium, were produced for the present work. Two steels kept the basic chromium content of the commercial alloy (0.40 to 0.60%), while this element was replaced with manganese in the other two steels. The chromium and manganese steels were produced with two levels of niobium. The Jominy hardenability, tensile properties, and impact and wear resistance of these materials were evaluated. A microstructural characterization was also performed. The results show that the developed steels can have the required hardness and strength levels. The high-niobium steels showed the best wear resistance but the poorest impact toughness. The wear resistance of the low-niobium steels was slightly higher and the impact toughness slightly lower than in the commercial alloy. The low-niobium steels show potential for commercial use.     

Dry sliding wear behavior of Al 2219/SiCp-Gr hybrid metal matrix composites

The dry sliding wear behavior of Al 2219 alloy and Al 2219/SiCp/Gr hybrid composites are investigated under similar conditions. The composites are fabricated using the liquid metallurgy technique. The dry sliding wear test is carried out for sliding speeds up to 6 m/s and for normal loads up to 60 N using a pin on disc apparatus. It is found that the addition of SiCp and graphite reinforcements increases the wear resistance of the composites. The wear rate decreases with the increase in SiCp reinforcement content. As speed increases, the wear rate decreases initially and then increases. The wear rate increases with the increase in load. Scanning electron microscopy micrographs of the worn surface are used to predict the nature of the wear mechanism. Abrasion is the principle wear mechanism for the composites at low sliding speeds and loads. At higher loads, the wear mechanism changes to delamination.     

Assessment of 3D printed steels and composites intended for wear applications in abrasive,dry or slurry erosive conditions

The design of earth cutting and machining tools generally requires the application of several types of materials with different wear resistance: (1) base metal with low wear resistance, (2) extremely resistant cutting inserts made of ceramics (or even diamond), cemented carbides or cermets and (3) thick coatings with average wear resistance to protect base metal or thin (PVD or CVD) coatings to improve wear resistance of inserts. The production of such tools is complicated, tedious and not very efficient (tool life depends on the interface bonding, brazed inserts can be severely damaged after impact, base material wear, etc.). The novel approach is to exclude the steps of brazing or coating and to produce steels or composites with similar wear resistance as that of inserts or coatings using the promising approach of additive manufacturing (AM i.e. 3D printing). Moreover, benefits of AM like near net shape part building with complex internal features (internal cooling channels) are desired for cutting tools. The aim of the current research is to assess novel commercially available 3D printed steels and composites in several relevant tribological conditions where these materials could be applied. The comparison with conventional Hardox 400 wear resistant steel and AISI 316 stainless steel is provided. Results report significant improvement in the wear resistance of AM produced steels and composites against reference materials. The performance of 3D printed materials lie between WC- based bulk cemented carbides and hardfacings. The characteristic features of wear mechanisms are presented and discussion is supported by Scanning Electron Microscope images.     

碳含量对低合金耐磨钢组织及耐磨性的影响

研究了碳含量分别为0.31%、0.38%和0.50%的低合金耐磨铸钢热处理后的组织、强韧性及不同磨损条件下的磨损性能。结果表明,试验钢经950℃淬火及250℃回火,显微组织均以板条马氏体为主,随含碳量的增加,组织有所粗化,并且有片状马氏体出现。试验钢的硬度随碳含量的增加而增加,但韧性下降。磨损试验结果表明,冲击磨料磨损条件下,主要表现为凿削磨损,碳含量为0.38%的试验钢具有较好的耐磨性;静磨料磨损条件下,主要表现为切削磨损,耐磨性主要受硬度的影响,碳含量为0.50%试验钢具有较好的耐磨性。     

不同含碳马氏体钢磨粒磨损后亚表层亚结构及性能变化的研究

用２０Ｃｒ、４０Ｃｒｓｉ、Ｔ８及Ｔ１０钢，通过热处理得到不同固溶碳量的马氏体，研究了其在静载三体磨粒磨损后亚表层亚结构与性能变化．结果表明：硬度沿亚表层分布规律及其耐磨性与马氏体固溶碳量相关，并与其亚结构变化相对应；磨损前后亚表层亚结构变化与其马氏体固溶碳量相关．     

Tribological evaluation of diamond coating on pure titanium in comparison with plasma nitrided titanium and uncoated titanium

Titanium alloys are characterized by poor tribological properties, and the traditional use of titanium alloys has been restricted to nontribological applications. The deposition of a well adherent diamond coating is a promising way to solve this problem. In this study, the tribological properties of diamond-coated titanium were studied using a pin-on-disk tribometer, and the results were compared with those of pure titanium and plasma nitrided titanium. The tribological behavior of pure titanium was characterized by high coefficient of friction and rapid wear of materials. Plasma nitriding improved the wear resistance only under low normal load; however, this hardened layer was not efficient in improving the wear resistance and the friction properties under high normal load. Diamond coating on pure titanium improved the wear resistance of titanium significantly. Surface profilometry measurement indicated that little or no wear of the diamond coating occurred under the test conditions loads. The roughness of the diamond coating was critical because it controlled the amount of abrasive damage on the counterface. Reducing the surface roughness by polishing led to the reductions in both the friction and wear of the counterface.     

等温淬火球铁(ADI)优越的耐磨性

等温淬火球铁(ADI),由于其强度高,韧性好,硬度高,有优越的耐疲劳性和特有的应变强化能力,因而具有优越的耐磨性.此外ADI还具有重量轻,成本低,能源消耗低,减震性好等特点.ADI已经成功地替代了多种炭钢和低合金钢铸件,锻钢件,表面淬火和氮化处理的钢件,铜合金铸件,组装件等,已经广泛应用于工业的各个部门,取得了明显的经济效益.文中列举了其在需要减小摩擦力的滑动摩擦条件下,需要摩擦力工作又要求耐磨条件下,磨料磨损以及某些特殊磨损条件下的应用实例.     

A quantitative estimation of the synergy between corrosion and abrasion

The corrosion wear rates of 304SS and 5140 steel at a sliding velocity of 0.025 ms⁻¹ and different loads in 3.5% NaCl solution were measured. The corrosion rates during rubbing and at steady state were also measured with the Tafel as well as the polarization resistance technique, respectively, and were calibrated by the results of immersion tests. The synergistic actions between corrosion and wear of the steels were analysed quantitatively. It shows that the corrosion-induced wear is the main cause of the material removal in the test conditions studied.     

25CrMnSi和22SiMn2低合金钢摩擦磨损性能研究

25CrMnSi和22SiMn2是两种低合金耐磨钢,为了研究其耐磨性能,通过滑动磨损与冲击磨损试验,测试并分析了两种材料的磨损形貌和金相组织。结果表明,在滑动磨损条件下,25Cr MnSi的表层和心部均比22Si Mn2耐磨,但二者心部的耐磨性差异更大;而在冲击磨损条件下,25Cr MnSi的耐磨性相对较差;在两种磨损条件下,25Cr MnSi耐磨失重量差异不大,而22Si Mn2在滑动磨损条件下的失重量几乎是冲击磨损的10倍,因而22Si Mn2较适合于冲击磨损情况下使用。     

冲击载荷的变化对不同含碳马氏体钢动载磨粒磨损系统耐磨性的影响

用２０Ｃｒ、４０ＣｒＳｉ和Ｔ１０三种材料，热处理成近乎单相马氏体组织，分别作为动载三体磨粒磨损试验的上、下耐磨试样，研究了冲击载荷的变化对系统耐磨性的影响。结果表明：在冲击功为１．０Ｊ时，具有高碳马氏体的Ｔ１０钢相互配副时，系统取得最佳耐磨性；当冲击功增加为３．６Ｊ时，具有中碳马氏体的４０ＣｒＳｉ钢的相互配副时，其系统耐磨性最佳。原因在于冲击载荷的变化，改变了磨粒对材料的作用方式，使磨损机制发生变化。     

Influence of Ni Content on Dry Sliding Wear Behavior of Sintered and Carburized Steels

The dry sliding wear behavior of two sintered and carburized steels with different Ni amounts has been investigated. The microstructure of the two steels comprises martensite, bainite, and the Ni-rich austenite. Under the sliding conditions investigated, wear is either oxidative or adhesive. In both cases, the lower amount of the soft Ni-rich austenite results in a better wear resistance. A design procedure for parts subject to dry sliding wear applications is proposed, based on the maximum acceptable wear depth, in order to evaluate the practical significance of the differences between the two materials.