Steel Pair Research Articles

Determination of Critical Stress for Dynamic Recrystallization of a High-Mn Austenitic TWIP Steel Micro-Alloyed with Vanadium

ABSTRACTWhen high strength and high ductility are required, the Twinning Induced Plasticity steels are an excellent choice. Their mechanical advantages are perfectly known in the automotive industry. Then, they are currently deeply studied. During the deformation at high temperature, TWIP steel experiences dynamic recrystallization. This mechanism results from dislocation interactions, and it depends of temperature, stress, strain, and strain rate. Experimental data give the maximum stress reached by the material, but the critical stress which determinates the DRX onset must be calculated from the strain hardening rate. Both stress and strain change simultaneously, and this variation gives the analytic data to determine σc, which is located at the inflection point of θ-σ plot. The main purpose of this paper was to study how the chemical composition and the experimental parameters (temperature and strain rate) affect the DRX, by the calculation and analysis of the σcvalues. Hot compression tests were applied to a pair of TWIP steels to compare the DRX onset and its relationship with the vanadium addition. The experimental variables were temperature and strain rate. The true stress–true strain plots were used to calculate σcby cutting data up to a previous point before the σpvalue, then, a polynomial fit and derivation were applied. The Zener-Hollomon parameter (Z) versus the stresses (peak and critical) plots show how the micro-alloying element vanadium improves the strain hardening in the analyzed TWIP steels.

Friction-Induced Oscillations of a Non-Asbestos Organic Pin Sliding on a Steel Disc

Abstract Friction-induced oscillations result in deterioration of performance of disc brakes and are generally undesired. We conduct experimental study of friction-induced oscillations in a non-asbestos organic material / steel pair used in disc brakes of motor vehicles. The tests are done by use of a pin-on-disc machine in which the pin sample is supported on a deformable beam. The adjustable friction parameters are the disc velocity, contact pressure and temperature. The tests show that the friction coefficient decreases with the sliding velocity and increases with the temperature. The friction-induced tangential oscillation of the pin sample occurs with a frequency equal to the first natural frequency of the beam. The effects of the disc velocity and temperature on the oscillation characteristics are investigated. The oscillation amplitude increases with the disc velocity on the interval of velocities below 2 m/s. Temperature changes of several tens of degrees Celsius lead to the oscillation occurrence / decay. The obtained results can be useful for prognostication of friction-induced oscillations in disc brakes with non-asbestos organic pads.

Effects of zinc on the laser welding of an aluminum alloy and galvanized steel

The fusion-brazing connection of 5052 aluminum alloy and ST07Z galvanized steel was achieved using a Nd:YAG laser, and the effects of the zinc layer on the forming properties of the fusion-brazing bead and the growth behaviors of the intermetallic compound (IMC) were investigated. The results indicate that the galvanized layer can particularly change the initial conditions of the brazing, reducing the brazing temperature from near the melting point of Fe (1535.0°C) to that of Al (660.4°C). The IMCs can transform from the Fe2Al5 and FeAl3 phases, which were observed in the interface of the aluminum/non-galvanized steel pair to the Fe2Al5Zn0.4 phase, which was observed in the interface of the aluminum/galvanized steel pair; this phenomenon occurs when zinc atoms are substituted for iron atoms during the formation of the IMCs.

Frictional study of alumina, 316 stainless steel, phosphor bronze versus carbon as mechanical seals under dry sliding conformal contact

This paper presents an investigative study on the frictional characteristics of alumina, 316 stainless steel, and phosphor bronze materials against resin-impregnated carbon in the form of mechanical seals. An experimental setup was designed and fabricated to study the frictional characteristics of the seal for varying normal load and speed. Pairing of stationary seal and rotary seal was done among the three combinations among which alumina versus resin-impregnated carbon exhibited the superior frictional characteristics. Whereas in comparison with 316 stainless steel versus resin-impregnated carbon and phosphor bronze versus resin-impregnated carbon, the latter exhibited the better frictional characteristics. Phosphor bronze pair and 316 stainless steel pair resulted in low and stable friction coefficient in the range of 0.07–0.08 and 0.12–0.13, respectively. This work highlights that the phosphor bronze might be an alternate substitute for the applications involving 316 stainless steel as a seal face material, where the frictional characteristics was a major concern.

Influence of Al2O3 particles on the friction and wear behaviors of nitrile rubber against 316L stainless steel

The friction and wear properties of nitrile rubber (NBR) against 316L stainless steel pairs were investigated by using a sphere-on-disc test device. The influence of Al2O3 particle sizes and the normal load on the tribological behaviors of the pairs were primarily evaluated. The damage behaviors of worn surfaces were analyzed using a scanning electric microscopy (SEM) and a surface profilometer. The results show that the friction coefficient decreased because of particles coming into contact pairs, while particles also play an important role in increasing the wear loss of stainless steel with many furrows on the steel ball surface due to the ploughing effect of hard particles. Large-sized particles could accelerate the wear of rubber, and the micro-cutting scratches of the stainless steel induced by the Al2O3 particles embedded in the rubber matrix. However, as the particle’s size decreased, the wear loss of the rubber was gradually mitigated. It is obvious that the normal load affected the wear of the rubber to a larger extent than the stainless steel. Moreover, with large particles, the wear loss of rubber increased sharply with increasing the normal load. In addition, the NBR/stainless steel tribo-pairs presented different wear mechanisms, under different conditions, such as having no particles or varied particle sizes.

Gaseous Tribochemical Products of Hydrogenated DLC Film and Stainless Steel Pair in Air Detected by Mass Spectrometry

A technique for detecting gaseous products in an air atmosphere was achieved based on a quadrupole mass spectrometer and a space-minimized sliding unit settled in a vacuum chamber for the purpose of controlling the flow of sample gas and increasing the concentration of products. The test results showed that when a hydrogenated DLC film was rubbed in a dry air environment, carbons were oxidized to form CO2. However, in a humid air atmosphere, water molecules competitively reacted with carbons to form hydrocarbons, so the oxidization of carbons by oxygen was inhibited. The different tribochemistry is thought to play an important role in the tribological behaviors of DLC films.

The influence of surface hardness on the fretting wear of steel pairs—Its role in debris retention in the contact

The influence of specimen hardness (between 275kgfmm−2 and 835kgfmm−2) in an AISI Type O1 steel-on-steel fretting contact was examined. In equal-hardness pairs, a variation in the wear volume of around 20% across the range of hardnesses examined was observed. However, in pairs where the two specimens in the couple had different hardnesses, a critical hardness differential threshold existed, above which the wear was predominantly associated with the harder specimen (with debris embedment on the softer specimen surface). This retention of debris provides protection of that surface from further wear and also results in accelerated wear of the harder counterface due to abrasion by the oxide debris bed which has built up on the opposing specimen.

Tribology of drawing lubricants for low carbon steel

Purpose – This paper aims to present a study of frictional characteristics of steel/die steel pair under sliding contact in presence of a set of formulated lubricants. AISI 1010 low carbon steels, although being strong, are less formable grades of steel and require appropriate selection of lubricants in tribological conditions. Design/methodology/approach – A total of three mineral-based lubricating blends were formulated for varying concentration of ester. Plan of experiments, based on Taguchi’s analysis technique were performed using dedicated test rig based on “pin-on-disc” principle. Findings – A correlation was established between additive concentration, sliding speed and pressure with coefficient of friction by multiple linear regression. On the basis of experimental results and S/N ratio analysis, ranking of the parameters has been done. A possible regime of working with such lubricants is also suggested. Practical implications – Due to voluminous data involved, a few dominant process parameters were taken into consideration for the study. Originality/value – This paper is highlighting the tribo-effects of additives to render it as suitable lubricant in sliding contact conditions. This paper also suggested an approach for selection of optimum regime of working in the light of “Stribeck Curve” for ester-containing lubricating oils.

Preparation and Tribological Properties of Surface-Capped Copper Nanoparticle as a Water-Based Lubricant Additive

Cu nanoparticle surface-capped by methoxylpolyethyleneglycol xanthate was synthesized using in situ surface-modification technique. The size, morphology and phase structure of as-prepared Cu nanoparticle were analyzed by means of X-ray diffraction and transmission electron microscopy. The tribological properties of as-synthesized Cu nanoparticle as an additive in distilled water were investigated with a four-ball machine, and the morphology and elemental composition of worn steel surfaces were examined using X-ray photoelectron spectroscopy and scanning electron microscope equipped with an energy-dispersive spectrometer attachment. Results show that as-synthesized Cu nanoparticle as a water-based lubricant additive is able to significantly improve the tribological properties and load-carrying capacity of distilled water, which is ascribed to the deposition of Cu nanoparticles on steel sliding surfaces giving rise to a protective and lubricious Cu layer thereon. In the meantime, they may also tribochemically react with rubbing steel surfaces to generate a boundary lubricating film consisting of Cu, FeS and FeSO4 on the rubbed steel surface, which helps to result in greatly improved tribological properties of distilled water, thereby reducing friction and wear of the steel–steel pair.

Comparative Study on the Wear Behavior of FPM and NBR in the Natural Crude Oil Medium

The wear behavior of stator rubber in the natural medium of crude oil in oil-drilling screw pumps directly matters to its service life and sealing property. The premature failure of stator rubber is the main cause for the shortening life of screw pumps. In order to study the wear mechanism of NBR and FPM, a friction wear test was conducted at room temperature by using a MPV-600 micro-computer-controlling grain-abrasion testing machine, in which NBR, FPM and 45# steal pair are the testing subjects. SEM was afterwards employed to observe the surface topography before and after the rubber wear. The test result shows that at the constant low load, the wear extent of FPM increases in a stable, linear way when the rotor rotating speed increases, and the wear extent of NBR increases with the increasing speed of the rotor rotating speed. However, when the rotating speed is over 400r/min, the wear extent of NBR decreases instead. This might be attributed to the improvement of the local lubrication state on the friction surface. Much consistence is indicated in the changing rule of the friction coefficient of the two types of rubber and the changing wear extent with the rotating speed. At the constant, low rotating speed, the wear extent of NBR and FPM basically increases linearly, while the friction coefficient of NBR, FPM and steel pair decreases with the increasing load.

Controllable Superlubricity of Glycerol Solution via Environment Humidity

The effect of humidity on the lubrication property of glycerol solution between steel surfaces has been investigated in this paper. A stable superlubricity with a friction coefficient about 0.006 has been found under the relative humidity between around 40% RH and 50% RH. Especially, it is noted that the lubrication state can be switched between superlubricity and nonsuperlubricity by adjusting humidity, which is attributed to the humidity-dependent hydrogen-bonding pattern in the solution. The mechanism of such superlubricity is attributed to the hydrated layer of water between the surface layers, which is formed by hydrogen-bonded glycerol and water molecules and strong enough to bear load, absorbed on each side of the solid surfaces. The work has potential applications, providing a simple and environment-friendly way to accomplish controllable superlubrication between steel pairs, which are commonly used in industry.

Study on Friction and Wear of Several Metal Materials under Oil Lubrication

The friction and wear properties of several common metal materials (45#, 25CrMn, and 40CrNiMo) friction pair under oil lubrication was investigated on M-200 Type wear tester, and studied the friction under the condition of differ sliding speed and pressure. The results show that: the 25CrMn/45# steel pair has better tribological and wear performance; the load is the main factor which influences the friction of the material at the low sliding speed; the main wear form is adhesive wear, but the wear mechanism is gradually became from adhesive wear to abrasive wear and flaking wear with the contact pressure and sliding speed increased.

Effect of Boron-Nitrogen Containing Modified Soybean Oil Lubricating Additive on Friction and Wear Behavior of Steel-Steel and Steel-Aluminum Alloy Systems

A type of new environmentally friendly lube additive---boron-nitrogen modified soybean oil was synthesized and characterized by infrared spectrum. Its effect on the friction and wear behavior of steel-steel and steel-aluminum alloy systems were investigated with a four-ball machine and an Optimol SRV friction and wear tester respectively. The morphographies of the worn surfaces were analyzed by means of scanning electron microscopy (SEM).The worn surfaces of the 2024Al alloy block were analyzed by means of X-ray photoelectron spectroscopy (XPS).The results show that the type of modified soybean oil as additives can obviously decrease the wear rate and friction coefficient of steel pair and steel-aluminum frictional pair. Its lubrication mechanism is inferred that a high strength adsorption film and/or tribochemistry reaction film on the worn surface of the Al alloy due the carrier effect of a long chain soybean oil, high reaction activities of nitrogen, electron-deficient of boron and their synergisms.

Multicomponent compositions of sulphurized rapeseed oil for lubrication of bronze – steel pair

У роботі представлені результати дослідження залежності інтенсивності зношування для пари бронза - сталь від вмісту компонентів мастильної композиції на основі хімічно-модифікованої ріпакової оливи. Показано, що при мінімальному вмісті сірки, трифенілфосфіну та бензотриазолу і високому вмісті дифенілтіосечовини у композиції спостерігаються мінімальні значення інтенсивності зношування оловофосфорної бронзи

Effects of electric current type and electrode configuration on the removal of Indigo Carmine from aqueous solutions by electrocoagulation in a batch reactor

The aim of this study is to investigate several electrode configurations and establish the effects of alternating current (AC), alternating pulse current (APC), and direct current (DC) on an electrocoagulation (EC) process conducted in a batch reactor. Indigo Carmine (IC) was considered as pollutant model. The investigated electrode configurations consisted in aluminum/aluminum, mild steel/mild steel, and aluminum/mild steel pairs. The effects of electrode configurations and current regimes on the removal efficiency, energy consumption, electrical operating costs, and electrode dissolution rate are discussed. The most powerful electrode configuration for IC removal from aqueous solutions by EC consisted in an anode of mild steel and a cathode of aluminum. EC operated in AC mode resulted in low efficiencies in any electrode configuration of those considered. Contrariwise, APC provided higher performance to the EC process in comparison with DC. Also, it led to higher dissolution rates in case of aluminum electrodes and to a more stable removal of dye when mild steel anode was employed. Energy-Dispersive X-Ray spectroscopy, Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) analytical methods were used to characterize the sludge separated by sedimentation and flotation in case of EC in APC mode using Al–Fe configuration. Thus, it was shown that IC dye was adsorbed on aluminum and iron hydroxides.

The Failure and Damage Mechanisms Under Friction of Copper in the EHL and Mixed EHL Regions

Recently, friction and wear behaviour of Copper (Cu)–steel pairs rubbed under different lubrication conditions were studied. The Stribeck curve was used to identify the different regimes of friction of copper with different virgin grain sizes: the elasto-hydrodynamic lubrication (EHL), mixed lubrication and boundary lubrication (BL) regimes. The aim of this work is the detailed analysis of the damage evolution under friction in the EHL and mixed EHL regions. The effects of load on the friction and the wear and damage mechanisms have been studied. The surfaces of Cu samples before and after friction have been analysed using SEM and AFM techniques as well as roughness and hardness measurements. It was shown that the mechanisms of damage and failure of Cu samples under friction in the EHL region are similar to the damage and failure mechanisms in Very High Cycle Fatigue. Friction in the EHL region is accompanied by initiation and coalescence of pores and microcracks. The effects of the coalescence of pores and microcracks observed in the EHL region are enlarged with a subsequent loading in the mixed EHL region. The effect of the loading rate on the transition from the EHL to BL region has been studied. It was shown that decreasing the loading rate increases significantly the load of the transition from the EHL to BL region. The pore and microcrack coalescence remain as the dominant damage mechanism under friction in the mixed EHL region with the low loading rate, while a lot of ploughing tracks and large delaminated regions appeared on the surface of Cu sample after friction with the higher loading rate.

Experimental Determination of the Coefficient of Friction in Rotational Sliding Joint

The friction processes as the most often physical phenomena cause many negative effects in production systems, and man try to minimize them. Coefficient of friction is one of the fundamental parameters which characterizes the process of friction between two parts, which perform mutual sliding of movement. Its measurement is realised using the experimental methods. In our experiments motion of samples is enforced motorically and various measurement sensors that monitor variables characterizing the process of friction are used. Experimentally obtained values of the coefficient of friction for the bushing aluminium - steel pairs are analysed in the paper. During the run up the value of the coefficient of friction sharply decreased from 0.8 to size 0.1 and then was stable till the end. Experimental tests were realised on the equipment Tribotestor M' 89, which was used for determination of the tribological parameters of bearing bushings. Following input variables were adjusted: the sliding speed, loading of rotanional sliding joint and duration of the test. The temperature in the contact surface of bushings and the roughness parameters (Ra, Rz) were also monitored before and after the tests.

Tribological behavior of the bronze–steel pair for worm gearing

The wear damage mechanisms occurring in the tribological pair bronze (CuSn12)-quenched and tempered steel (42CrMo4V) frequently used as reference materials for worm gearing power transmissions were investigated. Lubricated rolling sliding tests in the disk-on-disk configuration were performed. Different radial loads were applied in order to reach in the contact region Hertzian pressures close to the allowable design limit for bronze. The relative sliding speed was set to a level typical of screw-worm wheel transmissions. The tests were conducted up to a sliding distance of about 1800km and periodically interrupted for measuring the specimen's weight loss and for inspecting the surface modifications. At the end of the test, the wear curves (specific weight loss vs. sliding distance) were built up and the surface damage was analyzed by means of optical and scanning electron microscopy. Different damage phenomena as scoring, pitting, spalling were identified, whose severity depends on the applied load. Microstructural features, i.e. the interdendritic phase, strongly dictate the subsurface crack path and crack branching.

Coefficients of sliding friction of single crystals of high explosives under different rubbing conditions

The coefficients of sliding friction of single crystals of commonly used high explosives pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX) and beta-cyclotetramethylene tetranitramine (β-HMX) under several rubbing configurations and at a relative sliding speed of 0.22 mm s−1 were measured. The sliding configurations were (1) crystal–polished steel pairs, (2) like-crystal pairs and (3) unlike-crystal pairs. For every rubbing configuration the friction force showed oscillations, which are thought to be caused by the formation and shearing of the adhesive junctions formed at the surface of the rubbing crystals. This shearing of the adhesive junctions led to the formation of microscopic and sub-microscopic particles, which were confirmed by an environmental scanning electron microscope study. For every rubbing configuration and for relatively high normal loads pressing the rubbing crystals together, the coefficient of friction was generally in the range 0.2–0.25 and it has been concluded that the coefficient of friction is controlled by the adhesion with almost negligible contribution from the ploughing component. From a knowledge of the coefficient of friction and the uniaxial yield stress values of single crystals of RDX and β-HMX, the shear strength of these crystals were determined to be ∼13.4 MPa and ∼16.8 MPa, respectively.

Effect of Hardness and Position on Wear Behavior of Steel Pairs

In this paper, the effect of hardness and position on the 40CrNiMoA steel and 18Cr2Ni4WA steel friction pairs’ friction coefficient and wear volume were studied without lubrication, at room temperature. The results show that: Under test conditions, the fluctuation in the friction coefficient is bigger, when the up specimen is the harder 18Cr2Ni4WA steel. And when the up specimen is the softer 40CrNiMoA steel, the fluctuation in the friction coefficient is relatively small. When the up specimen is the 40CrNiMoA steel, the hardness of 40CrNiMoA steel is a relatively small impact on the average value of the coefficient of friction.When the up specimen is the softer 40CrNiMoA steel, the coefficient of friction is relatively larger than that when the up specimen is the harder 18Cr2Ni4WA steel. The wear volumes is relate to the position of friction pair. When the up specimen is the harder 18Cr2Ni4WA steel, both sides of the friction pairs has the same wear volumes when the hardness of 40CrNiMoA steel is about 43HRC. When the up specimen is softer 40CrNiMoA steel, and its hardness is about 54HRC, the wear volumes curves of two materials intersect.