Effects of yttrium on sliding wear of 304 stainless steel in dilute sulphuric acid and air

Abstract

Effects of an oxygen active element, yttrium, on the resistance of 304 stainless steel to corrosive siding wear in 0·1M H₂ SO₄ solution and to dry sliding wear in air, respectively, were investigated using a pin-on-disc wear tester. The worn surfaces and debris were examined by scanning electron microscopy. The results demonstrated that alloying with yttrium greatly improved the wear resistance of 304 stainless steel in both the corrosive and air environments.     

Improvement in the corrosion-erosion resistance of 304 stainless steel with alloyed yttrium

It has been previously demonstrated that yttrium can improve the resistance of stainless steel to sliding wear in corrosive environment. However, the mechanism responsible for the beneficial effect of yttrium on corrosive wear is not well understood. In this work, the erosion behavior of Y-free and Y-containing 304 stainless steel in a dilute H₂SO₄ slurry containing silica sand was investigated, with the aim of exploring the role that yttrium plays. The failure and self-healing of passive films on Y-free and Y-containing 304 stainless steel samples under combined attack by corrosion and mechanical scratch were studied, using an electrochemical scratch technique. The failure of the passive films during dry scratch and identation was also investigated using a micro-mechanical probe with in situ monitoring changes in the electrical contact resistance. In addition, effect of yttrium on electron work function was investigated. All the results demonstrated that yttrium effectively improved properties of the passive film, including corrosion resistance, mechanical behavior and the film stability, resulting in enhanced resistance to corrosion-erosion.     

Moisture-resistant MoS2-based composite lubricant films

The moisture resistance of sputter-coated composite films of MoS₂ can be markedly increased when the MoS₂ is sputter deposited with water-repellent additives. To increase the adhesion of such coatings and to prevent corrosive attack of the substrate, generally steel, a thin corrosion-resistant sulphide-forming intermediate layer is applied previously on the functional surface and serves as an interlayer.With a sputtering process coatings of these lubricants, which are durable in the Earth's atmosphere and adhere well to their support, are obtained. Friction and wear results for such composite lubricant films on different interlayers and various substrates, which were obtained in dry and humid air from pin and disc experiments and from functional bearing elements of precision engineering systems, confirm the improvements.     

Effect of Cl<Superscript>−</Superscript>on the corrosive wear of AISI 321 stainless steel in H<Subscript>2</Subscript>SO<Subscript>4</Subscript> solution

The effect of Cl⁻ on the corrosive wear behaviour of AISI 321 stainless steel in H₂SO₄ solution was studied via the corrosive wear rate, the load bearing capacity of passive film and the relationship between pitting and corrosive wear. There is a critical load at natural potential, below which the corrosive wear rate is slightly lowered by Cl⁻, while above which is increased. At natural potential there are more pits at low load than that at a higher one in the wear tracks and the pits are also deeper. The load bearing capacity is lowered by Cl⁻ at passive region and then the corrosive wear rate increased.     

The enhancement of wear properties of compressor oil using MoS2 nano-additives

MoS₂ nanoparticles have been considered valuable materials in lubricating applications due to their layered morphology. This work synthesized spherical MoS₂ nanoparticles that held many nanosheets through the hydrothermal method. The thickness of these sheets is between 10 and 25 nm, and their length is estimated to be about 200 nm. The effect of nanoparticles concentration on wear properties was investigated in this research. The four-ball test measured the wear performance of nano lubricants. The results showed that all nano lubricants had better wear performance than the base lubricant (Behran Compressor 68). However, molybdenum disulfide nanoparticles synthesized as nanosheets with a thickness of 10 nm had the best performance. At a concentration of only 0.05 wt-%, the resulting nano lubricant reduced the wear width and friction coefficient by about 50%. The thermal conductivity coefficient results also showed that nanoparticles increased this coefficient. As the lubricant temperature increases, the difference between the nano and base lubricant's thermal conductivity increases.     

Synthesis and tribological behavior of metakaolinite-based geopolymer composites

Metakaolinite-based geopolymer composites containing 5%–30% (volume fraction) scalelike graphite, polytetrafluoroethylene (PTFE), and molybdenum disulfide (MoS₂), respectively, were synthesized in the presence of a compound activator composed of aqueous NaOH and sodium silicate at room temperature. The tribological behaviors of the resulting composites sliding against AISI-1045 steel were investigated on an MM-200 friction and wear tester, and the bending strength and compressive strength of the composites were determined on a universal materials tester. Moreover, the worn surfaces of the composites were analyzed by means of scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS), which was aimed to reveal the wear mechanisms of the composites. It was found that all the three kinds of the tested solid lubricants contributed to greatly decrease the friction and wear of the composites, and they were also able to remarkably reduce the fluctuation of the friction coefficient. This was attributed to the formation of a lubricating film containing higher content of the detached solid lubricant particulates and the oxidized product Fe₂O₃ of the counterpart steel wear debris. The metakaolinite-based geopolymer was dominated by severe adhesion wear, while its composites filled with the solid lubricant particulates were characteristic of mild adhesion, scuffing, and delamination.     

Effect of solid lubricants on friction and wear behaviour of alloyed gray cast iron

Friction and wear behaviour of MoS₂, boric acid, graphite and TiO₂ at four different sliding speeds (1.0, 1.5, 2.0, 2.5?m/s) has been compared with dry sliding condition. MoS₂ and graphite show 30 to 50% reduction in mass loss compared to other lubricants at all sliding speeds. Friction coefficient reduces with increase in sliding speeds for all the conditions. Friction coefficient of dry as well as lubricant coated samples varies from 0.2 to 0.55 with MoS₂ showing the lowest value (0.2). Boric acid and TiO₂ coated samples show high friction coefficients at higher sliding speeds due to poor lubricity and adherence. This could also be due to sliding resistance offered by lubricant coated samples with predominant asperities interaction. MoS₂ and graphite coated samples also generated lowest frictional temperature compared to other conditions.     

纳米铜添加剂对重载车辆润滑油摩擦学性能影响的研究

采用化学反应法制备了表面修饰的纳米铜微粉,采用超声分散工艺分散于16#机油基础油中,利用T-11摩擦磨损实验机进行摩擦磨损试验。试验结果表明：不含纳米Cu的减摩添加剂和含纳米Cu的减摩添加剂添加到16#机油中,磨损量分别减少了19％、33％,减摩性能分别提高59％、86％。能谱分析表明磨痕表面不均匀的分布有铜元素,说明添加剂中的纳米铜在磨痕表面沉积,起到改善润滑油抗磨性能的作用。     

Effect of boronising on mechanical properties,wear and corrosion of N80 steel

Abstract

The effect of boronising on N80 steel tube was investigated by pack boriding. During the present investigation, microstructures of boride layer and substrate, hardness, mechanical properties, wear and corrosion were examined. In order to improve the tensile properties of the steel substrate after boronising, four different cooling methods were employed including annealing, air cooling, fan cooling and fan cooling with a graphite bar in the centre of boriding agent. Among these methods, the fan cooling with a graphite bar in the centre of the boriding agent makes the microstructure of ferrite and pearlite finest and the mechanical properties highest, in accordance with the mechanical properties required by API SPEC 5L. The borided N80 steel showed a better wear resistance at an applied load of 50 N with a sliding velocity of 0˙785 m s^–1, it also displayed a better corrosion resistance in both H₂SO₄ and HCl acid environments.     

Synthesis of a fullerene/expanded graphite composite and its lubricating properties

A fullerene/expanded graphite composite, in which fullerene crystals were incorporated into the expanded graphite interspaces, was prepared by chemical and thermal treatments and its lubricating properties in commercial grease were investigated. Expanded graphite, which was synthesized from graphite by oxidizing by KMnO₄ in 98% H₂SO₄ containing NaNO₃ and by heating at 400 °C for 3 min, and fullerene were placed in a stainless steel tube, and were heated in a furnace under vacuum at 600 °C for 2 weeks. The fullerene/expanded graphite composite obtained was characterized by X-ray diffraction analysis (XRD), Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM). XRD and FT-IR analyses showed that crystalline fullerene was present in the material and SEM images confirmed that it existed in the expanded graphite interspaces. The composite was blended with a commercial grease, and its lubricating properties were investigated using a four-ball lubricant tester. These properties were evaluated by measuring the wear scar diameter and wear volume loss of the test ball. The combination of composite and grease provided a better lubricating performance than that of pure graphite and grease.     

Microstructure and properties of ultrafine grain nickel 200 after hydrostatic extrusion processes

This paper presents the results of the studies of the structure and properties of ultrafine grained nickel 200 obtained by hydrostatic extrusion processes. Microstructure was characterized by means of optical microscopy and electron transmission microscopy. Corrosion resistance was studied by impedance and potentiodynamic methods using an AutoLab PGSTAT 100 potentiostat in 0.1 M Na₂SO₄ solution and in acidified (by addition of H₂SO₄) 0.1 M NaCl solution at pH = 4.2 at room temperature. Microhardness tests were also performed. The results showed that hydrostatic extrusion produces a heterogeneous, ultrafine-grained microstructure in nickel 200. The corrosive resistance tests showed that the grain refinement by hydrostatic extrusion is accompanied by a decreased corrosive resistance of nickel 200.     

轮缘固体润滑剂对轮轨减摩及损伤性能影响

用MMS-2A滚动摩擦磨损试验机完成试验工作,对比干态和3种不同固体润滑剂作用工况,分析干态和3种不同固体润滑剂作用后的轮轨摩擦性能和固体润滑剂的有效作用时间,探究固体润滑剂对轮轨摩擦性能的影响;分析不同工况下轮轨表面磨损量和表面裂纹,同时对裂纹的长度、角度、深度进行统计,分析固体润滑剂作用对轮轨损伤性能影响。结果表明:固体润滑剂具备减摩润滑作用,其中1号效果最佳,将干态下的摩擦系数0.5降低到0.2左右;固体润滑剂通过降低接触界面的摩擦系数减小轮轨界面的切向摩擦力,降低轮轨表面的磨损量,其中固体润滑剂1降低车轮和钢轨的磨损量最大,分别降低95.3%和97.1%;固体润滑剂主要通过抑制疲劳裂纹的长度来抑制轮轨疲劳裂纹的生长和扩展,通过正应力挤压作用使轮轨表面疲劳裂纹开口紧闭,缓解裂纹根部分支现象,有效抑制轮轨疲劳裂纹生长与扩展行为.     

The synergistic inhibition effect of rare earth cerium(IV) ion and iso-vanillin on the corrosion of cold rolled steel in 1.0 M H2SO4 solution

The synergistic inhibition effect of rare earth cerium(IV) ion and iso-vanillin (3-hydroxy-4-methoxy-benzaldehyde) on the corrosion of cold rolled steel (CRS) in 1.0 M H₂SO₄ solution was first investigated by weight loss and potentiodynamic polarization methods. The results revealed that iso-vanillin had a moderate inhibitive effect on the corrosion of CRS in 1.0 M H₂SO₄ solution, while cerium(IV) ion had a negligible effect. However, incorporation of Ce⁴⁺ with iso-vanillin significantly improved the inhibition performance. The inhibition efficiency for Ce⁴⁺ in combination with iso-vanillin was higher than the summation of inhibition efficiency for single Ce⁴⁺ and single iso-vanillin, which was synergism in nature.     

Frictional Properties of Tablet Lubricants

Abstract

Some frictional properties of tablet lubricants were determined. The friction coefficients and the adhesion forces of six lubricants were evaluated by the method proposed previously. The ejection force against the radial force for each lubricant yielded a straight line through the origin, so that the adhesion forces of these lubricants were estimated to be almost zero. All lubricants had low friction coefficients when they alone were compressed. The value for metal stearate was the smallest and that for talc was the largest. The affinity of the lubricants to the die wall, another important property of the lubricants, was also determined. After the die wall was conditioned by the tabletings of each lubricant alone, the serial tabletings of lactose granulates in the die were carried out. The increasing rate of ejection force in the conditioned die in a serial tableting was different for every pretreatment of each lubricant. The affinity of magnesium stearate to the die wall surface was superior to that of other lubricants.     

Chemie gegen Reibung und Verschleiß: Untersuchung molekularer Wirkungsmechanismen von Schmierstoffadditiven

Chemistry against friction and wear: Examining surface reactions of lubricant additives Although greases and oils are able to reduce friction without other substances being added, blending with additives is essential for todays high‐performance lubricants. Only these synthetic additives yield the desired characteristics of the final product, which is often designed specially for a particular application. In most cases, however, the underlying chemical mechanism is not exactly understood. For anti‐wear additives it will be shown how modern surface chemistry can help to understand the effectiveness of those substances and thus contribute to a systematic additive optimization.     

Nanodiamond-based nanolubricants for motor oils

Over the last few years, interest in applications of nanoparticles as lubricant additives has steadily grown due to the demonstrated reduction in friction and wear of nanoparticle-containing lubricant formulations (so-called nanolubricants). Particularly, studies of motor oils containing a “green” all-carbon additive, detonation nanodiamond (DND) particles, revealed their positive impact on the performance of lubricant compositions and fuel economy in engine tests. In the current review we discuss critical issues toward successful implementation of DND in nanolubricants: role of DND structural characteristics, stability of colloids of DND in oils, DND compatibility and synergism with other additives in commercial oils, mechanisms of DND impact on the properties of lubricants. Owing to the abrasive nature of diamond, DND-based nanolubricants must be carefully engineered in order to avoid increased wear of the friction surfaces and get full benefit from significantly reduced friction of well-polished surfaces.     

Ultraviolet absorption of cerium(III) and cerium(IV) in some simple glasses

The optical absorption spectra of cerium (III) and cerium (IV) in Na₂O-B₂O₃, Na₂O-SiO₂, Na₂O-P₂O₅ glasses, and in H₂O-H₂SO₄ and H₂O-H₃PO₄ solutions have been studied. Individual molar extinction coefficients of cerium (III) and cerium (IV) at different wavelengths (350 to 200 nm) have been estimated. In all the glasses and solutions, cerium (IV) produces a very strong and broad charge transfer band around 250 nm; the intensity, half-width, and position of this band change appreciably with glass composition. Cerium (III) in glass and in aqueous solution produces a number of absorption bands in the ultraviolet region corresponding to the f → d transitions. The cerium (III) bands are sharp and well resolved in Na₂O-P₂O₅ and in low-alkali borate glasses; the sharpness of resolution deteriorates in Na₂O-SiO₂, and in high-alkali borate glasses. The intensity of cerium (III) absorption also changes with glass composition. In all the glasses the molar extinction coefficient of cerium (IV) is 5 to 10 times stronger than that of cerium (III).     

Formation mechanisms of zinc,molybdenum, sulfur and phosphorus containing reaction layers on a diamond-like carbon (DLC) coating

Diamond-like carbon (DLC) coatings are nowadays successfully applied on industrial components like pistons, piston rings and bearings in lubricated tribological contacts due to friction and wear reducing effects. In contradiction thereto, todays lubricants and additives are designed for tribological steel/steel contacts, whereby the knowledge on tribochemical layer formation on steel surfaces is comprehensive in contrast to the physical-chemical interactions between diamond-like carbon coatings, lubricants and additives. Therefore the formation mechanisms of zinc, molybdenum, sulfur and phosphorus containing reaction layers on a zirconium modified diamond-like carbon coating a-C : H : Zr (ZrC_g) in lubricated tribological contacts were analyzed by means of pin-on-disc (PoD) tribometer by varying the distances from s = 200 m–3,000 m under boundary and mixed friction conditions at T = 90 °C and a contact pressure p = 1,300 MPa regarding the application of diamond-like carbon coatings on gears. The base lubricant poly-alpha-olefin (PAO) was formulated using the anti-wear (AW) and extreme pressure (EP) additive zinc dialkyldithiophosphate (ZnDTP) and the friction modifier (FM) additive molybdenum dialkyldithiophosphate (MoDTP). The chemical composition of the tribochemical reaction layers by means of and Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) as well as for the thickness differ significantly by varying the additivation.     

The extreme pressure and lubricating behaviors of potassium borate nanoparticles as additive in PAO

ABSTRACT

The potassium borate nanoparticles (nPB) as lubricant additive were prepared with an eco-friendly method. The tribological properties of nPB and ZDDP as lubricant additives in polyalphaolefin (PAO) were systematically evaluated using a four-ball tribometer and a SRV fretting friction and wear tester, which suggested that nPB exhibited excellent extreme pressure capacity, and better anti-wear and friction-reducing properties than ZDDP. Results of surface analyses show that the good lubricating properties and excellent load-carrying capacity of nPB in PAO are ascribed to the boundary protecting films, which were composed of some easy-shearing compounds: B₂O₃, Fe_xB_y and Fe₂O₃.     

Simple isolation method for the bulk isolation of wear particles from metal on metal bearing surfaces generated in a hip simulator test

Isolation and characterization of metal-on-metal (MoM) wear particles from simulator lubricants is essential to understand wear behaviour, ion release and associated corrosive activity related to the wear particles. Substantial challenges remain to establish a simple, precise and repeatable protocol for the isolation and analysis of wear particles due to their extremely small size, their tendency to agglomerate and degrade. In this paper, we describe a simple and efficient method for the bulk isolation and characterisation of wear particles from MoM bearings. Freeze drying was used to remove the large volume of water from the serum lubricant, enzymes used to digest the proteins and ultracentrifugation to finally isolate and purify the particles. The present study involved a total of eight steps for the isolation process and a wear particle extraction efficiency of 45% was achieved.