Wear properties of friction stir processed AISI D2 tool steel

Influences of microstructural and textural properties of friction stir processing (FSP) on dry reciprocating wear properties of AISI D2 tool steel are investigated in this study. The mechanical improvement is attributed not only to the homogenous distribution of very small carbides in a refined matrix, but also to significant development of textures during FSP. The excellent wear resistance is ascribed to nanohardness enhancement of the FSPed steel. Dominant shear components of {111} 〈110〉 and {112} 〈111〉 with the lowest Taylor׳s factor and the high density of close-packed planes formation significantly enhance the wear resistance of FSPed sample at 500 rpm.     

The microstructure and wear behaviour of friction stir processed AISI 430 ferritic stainless steel

ABSTRACT

The microstructure and wear behavior of Friction Stir Processed (FSPed) AISI 430 ferritic stainless steel were analyzed in the present study. FSP was performed with a tool rotation and advancing speeds of 1400?rpm 16?mm/min respectively by employing a tungsten carbide tool. The FSPed microstructure consisted of a mixture of ferrite and martensite. After FSP, microhardness increased with respect to that of the as-received material. The wear resistance of the FS processed material was significantly enhanced if compared to that of the as-received substrate. According to the SEM analyses of the worn surfaces and wear debris, a combination of adhesive wear and delamination was observed in the case of the base metal. The wear mechanism shifted to mild adhesive wear after FSP. The superior wear resistance of the FS processed AISI 430 steel was attributed to the pronounced grain refinement and to martensite formation in the stir zone.     

Effect of temperature on friction and wear of prehardened tool steel during sliding against 22MnB5 steel

Abstract

Mechanical components in tribological systems exposed to elevated temperatures are gaining increased attention since more and more systems are designed to operate under extreme conditions. In hot metal forming, the effect of temperature on friction and wear is especially important since it is directly related to process economy (tool wear) and quality of the produced parts (friction between tool and workpiece). This study is therefore focused on fundamental understanding pertaining to the tribological characteristics of prehardened hot work tool steel during sliding against 22MnB5 boron steel. The tribological tests were carried out using a high temperature reciprocating sliding friction and wear tester under a normal load of 31 N (corresponding to a contact pressure of 10 MPa), a sliding speed of 0·2 m s^?1 and temperatures ranging from 40°C to 800°C. It was found that friction coefficient and specific wear rate decreased at elevated temperature because of formation of compacted wear debris layers on the surfaces.     

Condition monitoring of first mode of metal transfer in friction stir welding by image processing techniques

This paper discusses a method for online condition monitoring of the friction stir welding (FSW) process using image processing techniques. Many FSW experiments are carried out at different process parameters and images of the first mode of the weld zone are captured. They are subsequently digitally processed and analysed using MATLAB to study the variations in the quality of weld, subjected to various conditions such as pin failure, and pin depth. This facilitates development of a methodology for online condition monitoring.     

High-temperature friction and wear behaviour of different tool steels during sliding against Al–Si-coated high-strength steel

The recent years have witnessed an increasing usage of high-strength steels as structural reinforcements and in energy-absorbing systems in automobile applications due to their favourable high-strength-to-weight ratios. Owing to poor formability, complex-shaped high-strength steel components are invariably produced through hot-metal forming. The high-strength steel sheets are in some instances used with an Al–Si-coating with a view to prevent scaling of components during hot-metal forming. However, friction and wear characteristics of Al–Si-coated high-strength steel during interaction with different tool steels have not yet been investigated. With this in view, friction and wear behaviours of different tool steels sliding against Al–Si-coated high-strength steel at elevated temperatures have been investigated by using a high-temperature version of the Optimol SRV reciprocating friction and wear tester at temperatures of 40, 400 and 800 °C. In these studies both temperature ramp tests with continuously increasing temperature from 40 to 800 °C and constant temperature tests at 40, 400 and 800 °C, have been conducted. The results have shown that both the friction and wear of tool steel/Al–Si-coated high-strength steel pairs are temperature dependent. Friction decreased with increasing temperature whereas wear of the tool steel increased with temperature. On the other hand, the Al–Si-coated high-strength steel showed significantly lower wear rates at 800 °C as compared to those at 40 and 400 °C. The Al–Si-coated surface undergoes some interesting morphological changes when exposed to elevated temperatures and these changes may affect the friction and wear characteristics. The mechanisms of these changes and their influence on the tribological process are unclear and further studies are necessary to fully explain these mechanisms.     

On the surface and tribological characteristics of burnished cylindrical Al-6061

Surface treatment is an important aspect of all manufacturing processes to impart specific physical, mechanical and tribological properties. Burnishing process is a post-machining operation in which the surface irregularities of the workpiece are compressed by the application of a ball or roller. In the present study, simple and inexpensive burnishing tools, with interchangeable adapter for ball and roller were designed and fabricated. Ball burnishing processes were carried out on aluminium 6061 under different parameters and different burnishing orientations to investigate the role of burnishing speed, burnishing force and burnishing tool dimension on the surface qualities and tribological properties. The results showed that burnishing speed of 330 rpm and burnishing force of 160 N produce optimum results. Meanwhile, a decrease in the burnishing ball diameter leads to a considerable improvement in the surface roughness up to 75%. On the other hand, parallel burnishing orientation exhibits lower friction coefficient compared to cross-burnishing orientation. Furthermore, ball burnishing process is capable of improving friction coefficient by 48% reduction and weight loss by 60-80% reduction of burnished surface of aluminium 6061. These findings are further supplemented by the surface features as seen in SEM photomicrographs.     

Influence of ball burnishing on surface quality and tribological characteristics of polymers under dry sliding conditions

In this paper, the application of ball burnishing as a new surface treatment process for polymers is investigated. The polymers used were polyoxymethylene (POM) and polyurethane (PUR). The lowest surface roughness value achieved for POM was 0.44 μm (45% decrease) and for PUR was 0.46 μm (42% decrease). The lowest coefficient of friction value achieved was 0.22 (32.9% decrease) for POM and 0.24 (28.8% decrease) for PUR. The lowest specific wear rate value achieved was 0.31×10⁻⁶ mm³/N m (38.6% decrease) for POM and 0.41×10⁻⁶ mm³/N m (37.9% decrease) for PUR.     

Effect of process parameters on the macrostructure and defect formation in friction stir lap welding of AA5456 aluminum alloy

Friction stir welding could be considered as a suitable technique for joining of aluminum alloys due to the emerging of different problems in fusion welding of these alloys, especially in lap joint designs. For this purpose, it is necessary to optimize the process parameters while in this study, the combined effects of tool rotation and welding travel speed on the macrostructure and defect formation of friction stir lap welding of AA5456 was investigated. The rotating tool was plunged from the 5 mm-thick AA5456-H321 (top sheet) surface into the 2.5 mm-thick AA5456-O (bottom sheet) and lap joints were fabricated by rotational speeds of 300, 600, 800 and 1000 rpm and welding speeds of 15, 30, 60 and 100 mm min⁻¹. The effect of tool rotation and welding speed on the macrostructure, material flow and defect formation, i.e. hooking, kissing-bond and cavity, were studied by optical microscopy and scanning electron microscope. The results declared that hooking height decreased as the welding speed increased while kissing-bond was formed at higher welding speeds. Moreover, hooking region was extended as the tool rotational speed increased. However, at a high rotational speed, cavity was even created.     

Effect of matrix morphology on the wear and friction behavior of alumina nanoparticle/poly(ethylene) terephthalate composites

The friction and wear properties of poly(ethylene) terephthalate (PET) filled with alumina nanoparticles were studied. The nanoparticle loading was varied from 1 to 10 wt.%. The nanocomposite samples were tested in dry sliding against a steel counterface. The results show that the addition of nanoparticles can increase the wear resistance by nearly 2× over the unfilled polymer. The average coefficient of friction also decreased in many cases. The nanocomposites form a more adherent transfer film that protects the sample from the steel counterface, although the presence of an optimum filler content may be due to the development of abrasive agglomerates within the transfer films in the higher wt.% samples. This study varied both crystallinity and weight percent of filler in a PET matrix in an attempt to separate the effects of nanofillers and crystallinity on the tribology.     

火箭贮箱环缝搅拌摩擦焊外定位床身的设计与研究

针对火箭贮箱卧式搅拌摩擦焊的焊接特点,设计了集主驱动和外定位于一体的焊接机床.对底箱、环座和压环等机床床身的主要零/部件进行了强度、刚性分析,并验证其对火箭贮箱焊接质量的影响;解决了火箭贮箱焊接时扭转力矩偏大、定位精度低以及焊接扭转错缝等难题.推动了我国火箭贮箱搅拌摩擦焊的工程化应用,为后续相似装备的设计开发提供了实际...     

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.     

Effect of surface coating and tin plating on friction characteristics of P-110 tubing for different thread compounds

Design factor problems related to galling failure have become an increasing concern for deepwater offshore wells. This paper presents the results of an experimental study conducted to determine friction characteristics of P-110 tubing coated with manganese phosphate and plated with tin. Six repeated tests were run to investigate the effect of lubrication type on friction characteristics of P-110 tubing by using thread compounds of API modified Threadkote-706, Shell Type-3 and Graphite/PTFE at a rotational speed of 5 rpm. In each test the bearing load was increased monotonically to a maximum value of 625 kN. The results of this study clearly indicate the importance of tin-plating in reducing the coefficient of friction.     

Influence of surface texture and roughness parameters on friction and transfer layer formation during sliding of aluminium pin on steel plate

Surface texture of harder mating surfaces plays an important role during sliding against softer materials and hence the importance of characterizing the surfaces in terms of roughness parameters. In the present investigation, basic studies were conducted using inclined pin-on-plate sliding tester to understand the surface texture effect of hard surfaces on coefficient of friction and transfer layer formation. A tribological couple made of a super purity aluminium pin against steel plate was used in the tests. Two surface parameters of steel plates, namely roughness and texture, were varied in the tests. It was observed that the transfer layer formation and the coefficient of friction along with its two components, namely, the adhesion and plowing, are controlled by the surface texture and are independent of surface roughness (R_a). Among the various surface roughness parameters, the average or the mean slope of the profile was found to explain the variations best. Under lubricated conditions, stick–slip phenomena was observed, the amplitude of which depends on the plowing component of friction. The presence of stick–slip motion under lubricated conditions could be attributed to the molecular deformation of the lubricant component confined between asperities.     

Study of tribological performance of ECR-CVD diamond-like carbon coatings on steel substrates: Part 1. The effect of processing parameters and operating conditions

Diamond-like carbon (DLC) coatings were prepared on AISI 440C steel substrates at room temperature by electron cyclotron resonance chemical vapor deposition (ECR-CVD) process in C₂H₂/Ar plasma. Using the designed Ti/TiN/TiCN/TiC interfacial transition layers, relatively thick DLC coatings (1-2 μm) were successfully prepared on the steel substrates. The friction and wear performance of the DLC coatings was evaluated by ball-on-disk tribometry using a steel counterbody at various normal loads (1-10 N) and sliding speeds (2-15 cm/s). By optimizing the deposition parameters such as negative bias voltage, DLC coatings with hardness up to 30 GPa and friction coefficients lower than 0.15 against the 100Cr6 steel ball could be obtained. The friction coefficient was maintained for 100,000 cycles (∼2.2 km) of dry sliding in ambient environments. In addition, the specific wear rates of the coatings were found to be extremely low (∼10⁻⁸ mm³/Nm); at the same time, the ball wear rates were one order of magnitude lower. The influences of the processing parameters and the sliding conditions were determined, and the frictional behavior of the coatings was discussed. It has been found that higher normal loads or sliding speeds reduced the wear rates of the coatings. Therefore, it is feasible to prepare hard and highly adherent DLC coatings with low friction coefficient and low wear rate on engineering steel substrates by the ECR-CVD process. The excellent tribological performance of DLC coatings enables their industrial applications as wear-resistant solid lubricants on sliding parts.     

Effect of counterpart on the tribological behavior and tribo-induced phase transformation of Si

The tribological behaviors and phase transformation of single crystal silicon against Si₃N₄, Ruby and steel were investigated in this study. It was found that the strong chemical action between silicon and Fe was the key factor to the tribological behavior of silicon as slid against steel. SEM and Raman spectroscopy indicated that phase transformation of single crystal silicon occurred during the running-in period at low sliding velocity as slid against Si₃N₄ and Ruby, and gave birth to single or a mixture phase of Si-III, Si-XII and amorphous silicon. The high hardness of counterpart and the absence of chemical action between silicon and counterpart facilitated the phase transformation of single crystal silicon.     

Effect of counterparts on the friction and wear behavior of polyelectrolyte multilayers

Polyelectrolyte multilayers (PEMs) were prepared on Si substrates by alternative deposition of poly(sodium 4-styrenesulfonate) (PSS) as polyanion and poly (diallyldimethylammonium chloride) (PDDA) as polycation. The PEM film was characterized by means of ultraviolet-visible light absorption spectrometry and atomic force microscopy. The friction and wear behavior of the polymer film sliding against brass, 440C stainless steel, Si₃N₄ and WC balls was evaluated on a microtribometer. It was found that the multilayer film was uniform and compact, and it registered a lowered friction coefficient and extended antiwear life while sliding against soft counterparts, in particular, a brass ball. This could be because the polymeric transfer film had an enhanced adhesion on the soft metallic counterpart in the presence of inter-transferred metallic debris. Contrary to the above, the PEM film had a higher friction coefficient and shorter antiwear life while sliding against Si₃N₄ and WC balls, possibly owing to a higher shearing stress in the presence of stiff and hardly deformable hard counterparts. In other words, the polymeric transfer film on the hard couterparts, if any, would be easily scaled off, leading to decreased antiwear life. Moreover, the differences in the friction and wear behavior of the PEM film sliding against different counterparts were closely related to the differences in the chemical and crystallographic structure of the counterparts (ceramics Si₃N₄ and WC, and metals brass and stainless steel).     

The Effects of Dopants on the Chemistry and Tribology of Sputter-Deposited MoS2 Films

The fact. that dopants improve the friction and wear properties of sputtered MoS₂ films is well known. However, the role of dopants in the mechanisms governing friction and wear are not well understood. The purpose of this work is to gain a fundamental understanding of their role by co-depositing a number of materials, i.e., Ni, Fe, Au, and. Sb₂O₃, with MoS₂ and evaluating their effects on film chemistry, crystallinity, microstructure, and tribology. Friction and wear measurements were collected, using ball-on-flat and dual-rub shoe tribom-eters. Other physical and chemical properties were obtained using SEM, XPS, XRD) and Raman spectroscopy. Crystalline MoS₂ was seen in all of the films. In Sb₂O₃-doped films, an amorphous phase was also observed. The presence of dopants caused film densification and affected crystallite size. They had little effect on the overall crystallite orientation. In addition, dopants caused a reduction in the mean and. variance of the friction coefficient and an increase in wear life. The correlation between dopants, film properties, and tribology is discussed in detail.     

摩擦火花瞬时高温对中高碳钢中碳的影响

选取42CrMo、60Si2Mn、GCr153种常见的中高碳钢理论分析和检测验证两方面对高速打磨过程中摩擦火花瞬时高温是否会对中高碳钢表面形成脱碳层,从而影响中高碳钢中碳含量的检测进行探讨、验证。结果表明高速打磨过程中摩擦火花瞬时高温无法达到中高碳钢表面脱碳所需的温度,并且在实际检测中标准物质11次测试结果的RSD在0.499%~0.698%,测试结果的平均值和认定值的差值均在标准样品证书的不确定度范围内。因此高速打磨过程中摩擦火花瞬时高温不会影响中高碳钢中碳含量的检测。     

Friction and wear characteristics of ZDDP in the sliding of steel against aluminum alloy

The tribological properties of zinc dialkyldithiophosphate (ZDDP) antiwear additives in the sliding of steel against aluminum alloy were investigated by an oscillating friction and wear apparatus, an Optimol SRV tester. It was found that ZDDP produced larger wear of aluminum alloy than base stock, especially at high concentration. The acting mechanism of ZDDP in the lubricated aluminum-on-steel system was proposed.     

大型覆盖件拉深成形的摩擦特性与摩擦学设计

分析了大型覆盖件拉深成形的摩擦特性,比较了各种润滑剂的润滑性能及润滑剂的选择,指出了摩擦学设计应考虑的问题,对大型覆盖件拉深成形具有指导意义.