Rolling-sliding wear on precipitation-hardened structures of an austenitic steel

Microstructures of equal and different hardnesses were produced by the aging of a precipitation-hardened austenitic steel. This material was used as a model for studying the effects of microstructural elements on rollingsliding wear on underaged and overaged or peak-aged and thermomechanically treated structures of equal hardness. The effect of different hardness was evaluated by comparing the underaged and peak-aged structures. Model wear tests were run using a marginally lubricated contact by using an Amsler A 135 tribometer. The results can be interpreted in terms of the resistance to plastic deformation and the crack formation and crack growth behaviour of the different structures. The latter was studied using the usual fatigue and crack growth tests.     

Evolution of friction-induced microstructure of SUS 304 meta-stable austenitic stainless steel and its influence on wear behavior

The microstructure evolution of the worn surface and sub-surface layer of SUS 304 austenitic stainless steel (ASS) disc against Al₂O₃ ceramic ball were studied on the basis of the tribological behaviors in the tests performed using a Cameron-Plint TE67 pin-on-disc tester. The microstructure after friction test was observed by optical and scanning electron microscope. The possible phase transformation of meta-stable austenite to martensite was detected by X-ray diffractometer. Results showed that friction-induced deformation led to finer grain at the subsurface beneath the worn surface. Furthermore, white layer was observed on some worn surface layers after higher normal loads. Transformed martensite from the austenite appeared on the worn surface under both low and high normal-loading conditions. Absence of transformed martensite was detected at the site about 25 μm below the worn surface although the grains at the site were still intensive and fine. In addition, the specific wear rate of SUS 304 stainless steel specimens was measured, and the possible reasons affecting the wear behavior were analyzed and discussed.     

The fretting wear of an austenitic stainless steel in air and in carbon dioxide at elevated temperatures

The development of an experimental test facility designed to investigate the fretting wear of metals in high temperature gaseous atmospheres is described briefly. Small amplitude torsional fretting was produced between normally loaded annular contact surfaces at temperatures up to 650 °C. The information presented concerns the effects produced on fretting a type 321 stainless steel in air and CO₂ environments. Use of electron optical and surface profiling techniques has allowed a qualitative asessment of the degree and characteristic features of the damage to specimens fretted at room temperature and 650 °C under selected oscillatory wear conditions. During simultaneous oxidation and fretting at 650 °C the initially formed protective oxide is disrupted exposing a chromium-depleted surface which subsequently oxidizes to a less protective Fe-Cr spinel. This combination of effects could have unfortunate consequences on the long term wear behaviour.     

Sliding wear behaviour of an electrochemically modified austenitic high-nitrogen steel surface

Wear debris from artificial metallic implant joints is known to provoke detrimental foreign-body reactions in the surrounding human tissue. Although commonly used biotolerant metals generate only a little amount of particles, wear is still a major cause for concern. It is the aim of this work to evaluate the sliding wear resistance of a topologically modified high-nitrogen austenitic stainless steel. A disc-on-pin test in self-mating contact is performed in distilled water. Submicron particles are trapped by the structured topography and form together with the plastically deformed metal a hybrid surface which has the potential to significantly improve the tribological behaviour of the tested high-nitrogen steel.     

Fatigue crack growth behavior in ultrafine grained low carbon steel

Ultrafine grained (UFG) low carbon (0.15 wt.% C) steel produced by equal channel angular pressing (ECAP) was tested for investigating the effect of load ratio on the fatigue crack growth rate. Fatigue crack growth resistance and threshold of UFG steel were lower than that of as-received coarse grained steel. It was attributed to the less tortuous crack path. The UFG steel exhibited slightly higher crack growth rates and a lower ΔK_th with an increase of R ratio. The R ratio effect on crack growth rates and ΔK_th was basically indistinguishable at lower load ratio (R>0.3), compared to other alloys, which indicates that contribution of the crack closure vanishes. The crack growth rate curve for UFG steel exhibited a longer linear extension to the lower growth rate regime than that for the coarse grained as-received steel.     

Corrosive wear of carbon and austenitic stainless steels in NaCl solution

The wear rates of an AISI 52100 carbon steel and a type 316 austenitic stainless steel and the corrosion current I from the rubbing steels were measured in NaCl solution to study the interrelationship between the corrosion and wear of the steels. An on-off cyclic loading test was also conducted to examine the effect of static corrosion during an unloading period on the corrosive wear of the steels.

It was found that the wear rates of the carbon steel and the type 316 stainless steel reach a maximum at NaCl concentrations of about 3% and 0.1% respectively. The on-off cyclic test has shown that corrosive wear of the steels is influenced by static corrosion during an unloading period. The increment †I of the corrosion current due to sliding was associated with the corrosive wear rate of the steels.     

Micro-defects on machined carbon steel surfaces

Contrary to the evidence of stylus instruments, the residual roughness of machined 0.35% carbon steel surfaces changes as a function of cutting speed. The origin of the microdefects, observed by electron microscopy and, with one exception, unresolved by conventional roughness measurement techniques, is thought not to be any malfunction of the machining process, but inherent in the process of surface formation. This paper describes micro-defects considered relevant to contacting surfaces and indicates that cutting speed selection for finish machining of tribological components based on conventional roughness measurements is questionable.     

Transition of the lubricated wear of carbon steel

To study the transition of the lubricated wear of 0.53% C steel in the steady state, wear tests were carried out by rubbing the annular surfaces of two cylindrical test pieces in machine oil with no additives. The ratio of mating areas was varied to approach actual contact conditions. Three regions of variation in the coefficient of friction with contact load were determined. Fatigue wear, characterized by a friction coefficient μ ≈ 0.05 and a specific wear rate ω_s ≈ 0.005 × 10^?6 mm³ N^?1 m^?1, occurs in the first region.A transition from fatigue wear to adhesive wear, with μ ≈ 0.05?0.12 and ω_s ≈ (0.005?0.05) × 10^?6 mm³ N^?1 m^?1, takes place gradually within a specific load range. Finally, adhesive wear predominates above the load level that marks the end of the transition. The same behaviour was analysed through stepwise loading tests. The onset of transition and seizure occurs at constant mean surface temperatures. However, the end of transition is also affected by factors other than temperature. The results are compared with the transitions reported by the International Research Group on Wear of Engineering Materials of the Organization for Economic Cooperation and Development.     

Micro-defects on machined carbon steel surfaces

Contrary to the evidence of stylus instruments, the residual roughness of machined 0.35% carbon steel surfaces changes as a function of cutting speed. The origin of the micro-defects, observed by electron microscopy, and with one exception, unresolved by conventional roughness measurement techniques, is thought not to be any malfunction of the machining process, but inherent in the process of surface formation. This paper describes micro-defects considered relevant to contacting surfaces and indicates that cutting speed selection for finish machining of tribological components based on conventional roughness measurements is questionable     

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.     

The wear of high density polyethylene sliding against steel surfaces

The wear of high density polyethylene sliding against steel surfaces was studied with a pin-on-disc machine. The disc surfaces were finished by a turning operation on a lathe, changing the cutting conditions and tool geometries so as to provide varying surface finishes and different numbers of asperity peaks per unit distance. Optical and scanning electron microscopy were used to study the wear particles and the transfer films. It is found that a polymer film composed of layers about 500–1000 Å thick is formed on the metallic surfaces with sharp asperities. The size of the polymer wear particles decreases with increasing number of asperity peaks per unit distance and with decreasing asperity angle. The steady state wear rate increases rapidly with increasing polymer wear particle size. The wear for polymermetal sliding occurs by the mechanism of abrasion.     

Medium carbon steel alloy design for wear applications

The fracture characteristics of steels are strongly influenced by martensite substructure, retained austenite stability, and morphology. Attractive strength-toughness properties have been attained with Fe-Cr-C-Mn alloys. These alloys, when tested under sliding wear conditions, also exhibit good wear resistance which compares favorably with that of commercial wear-resistant alloys. The most significant finding is an apparently strong correlation between sliding wear resistance and retained austenite, which in turn appears to correlate with Charpy impact properties. Little correlation was observed between hardness and wear resistance for the experimental steels.     

Friction and wear behavior of diamond-like carbon coating on plasma nitrided mild steel under boundary lubrication

The friction and wear properties of synthetic ionic liquid functionalized borate esters as additives in poly-alpha-olefin (PAO) were measured for diamond-like carbon (DLC) coating on plasma nitrided AISI 1045 steel. Results show that the borate esters gave much better friction–reduction and antiwear properties for DLC coating/steel and DLC coating/DLC coating sliding pairs than zinc dialkyldithiophosphate (ZDDP). In addition the DLC coating had much better wear resistance than the nitrided mild steel substrate, indicating that duplicate surface modification was more effective in significantly increasing the wear resistance of mild steel.     

Friction, wear and material transfer of sintered polyimides sliding against various steel and diamond-like carbon coated surfaces

Polyimide cylinders are slid under 50 N normal load and 0.3 m/s sliding velocity against carbon steel (R_a=0.2 and 0.05 μm), high-alloy steel (R_a=0.05 μm), diamond-like carbon (DLC, R_a=0.05 μm) and diamond-like nanocomposite (DLN, R_a=0.05 μm). Only for a limited range of test parameters, the friction of polyimide/DLN is lower than for polyimide/steel, while polyimide shows higher wear rates after sliding against DLN compared to steel counterfaces. The DLN coating shows slight wear scratches, although less severe than on DLC-coatings that are worn through thermal degradation. Therefore, also friction against DLC-coatings is high and unstable. Calculated bulk temperatures for steel and DLN under mild sliding conditions remain below the polyimide transition temperature of 180 °C so that other surface characteristics explain low friction on DLN counterfaces, as surface energy, structural compatibility and transfer behaviour. Friction is initially determined through adhesion and it is demonstrated that higher surface energy provides higher friction. After certain sliding time, different polyimide transfer on each counterface governs the tribological performance. Polyimide and amorphous DLC structures are characterised by C–C bonds, showing high structural compatibility and easy adherence of wear debris on the coating. However, it consists of plate-like transfer particles that act as abrasives and deteriorate the polyimide wear resistance. In sliding experiments with high-alloy steel, wear debris is washed out of the contact zone without formation of a transfer film. Transfer consists of island-like particles for smooth carbon steel and it forms a more homogeneous transfer film on rough carbon steel. The latter thick and protective film is favourable for low wear rates; however, it causes higher friction than smooth counterfaces.     

Improved work-hardening ability and wear resistance of austenitic manganese steel under non-severe impact-loading conditions

An investigation into the work-hardening mechanism and the method of improving the work-hardening ability and the wear resistance of austenitic manganese steel, under non-severe impact-loading conditions, by means of transmission electron microscopy and X-ray diffraction has been conducted in this project. The results indicate that the work-hardening effects result from increased dislocation density and stacking faults for the manganese steel with higher austenite stability, while they result from the combined effects of dislocation strengthening and strain-induced martensite for manganese steel with lower austenite stability. By comparison with Hadfield steel, the work-hardening ability and the wear resistance of the austenitic medium manganese steel increase by 60%–120% (the highest surface hardness up to 700 HV) and 50%–140% respectively, if the chemical compositions and technology are properly controlled, to obtain suitable austenite stability and secondary phase hard particles.     

Wear and corrosion wear of medium carbon steel and 304 stainless steel

Wear and corrosive wear involve mechanical and chemical mechanisms and the combination of these mechanisms often results in significant mutual effects. In this paper, tribological behavior, X-ray peak broadening, and microstructure changes of carbon steel AISI 1045 and stainless steel AISI 304 samples under simultaneous wear and corrosion were investigated and the results were compared with those obtained from dry wear tests. 3.5 wt.% NaCl solution was used as the corrosion agent and a pin-on-disk tribometer was employed to perform wear and corrosive wear tests.X-ray diffraction measurements have shown that by increasing the applied load, the worn surfaces of carbon steel samples reached a constant strain at which fracture and wear occurred. Whereas in 304 stainless steel samples, by increasing the applied load, broadening of X-ray diffraction peaks was decreased.Wear tests of carbon steel and stainless steel samples have shown smaller weight losses and lower friction coefficient in the presence of corrosive environment. Study of worn surfaces suggested that depending on wear environment and applied load, different features of wear mechanisms were involved.     

激光熔覆涂层在多冲载荷下的力学行为分析

根据多次冲击载荷的特性,从应力波传播、多冲磨损、多冲硬化与软化和多冲塑性变形方面,对带有激光熔覆层试样在多冲冲击载荷下的部分力学行为进行了试验研究。结果表明：在多冲载荷作用下,应力波在涂层和基体的;台金接合面发生反射,形成拉伸波造成涂层的纵裂和角裂;在涂层表面由于应力集中,涂层表面发生微观点蚀和深层剥落;冲击载荷能量的积累．造成涂层试样硬度变化和塑性变形。     

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.     

爆炸焊接复合钢板制复合管耐腐蚀性能研究

以825合金为内覆层材料,L415QS(X60)管线钢为基层材料,采用爆炸复合钢板和折弯成型(JCO成型)工艺制造了一根长度12 m的复合管,对其管体和焊缝的内覆层825合金进行了晶间腐蚀、点腐蚀和应力腐蚀性能试验,晶间腐蚀和点腐蚀的试验结果和原材料相当,在模拟酸性油气田工况介质的应力腐蚀试验中评定合格.