Steel Pair Research Articles

Microstructural studies and impact toughness of dissimilar weldments between AISI 316 L and AH36 steels by FCAW

In this study, AISI 316 L austenitic stainless steel and AH36 low-alloy ship building steel pair were joined with flux-cored arc welding method by using E309LT1-1/4 filler metal under four different shielding gas compositions containing CO2 at different ratios. Microstructure, impact toughness of welded materials, and their microhardness distribution throughout joining were determined. In macro- and microstructure examinations, stereo optical microscope, scanning electron microscope (SEM), SEM/energy dispersive spectroscopy, and SEM/mapping analysis techniques were used. After notched impact toughness, fracture surfaces were examined using the scanning electron microscope. This study investigated effects of shielding gas composition on microstructure, impact toughness, and microhardness distribution of transition zone between AH36 steel and weld metal of joined material. It is observed that based on an increase in amount of CO2 in shielding gas, impact toughness values of the weldment decreased. Microhardness values change throughout weld metal depended on shielding gas composition. Moreover, an increase in amount of CO2 within shielding gas decreased δ-ferrite amount in weld metal. The increase in amount of CO2 within shielding gas leads to expanded transition zone in interface between AH36 and weld metal and also affects notched impact toughness values negatively due to the inclusion amounts occurring in weld metal and hence caused it to decrease.

Study on the frictional properties of micro-magnet arrayed surface lubricated with ferrofluids

Ferrofluids (FF) are stable colloids exhibiting normal liquid behavior coupled with magnetic properties. As a kind of lubricant, the most obvious advantage is that FF can be maintained in the desired position without any leakage by applying a permanent magnet. For the above characteristics, a kind of micro-magnet arrayed surface for FF lubrication was introduced in this article. The tribological performances of the surface were tested under plane contact conditions using FF as a lubricant. Flat SUS316 steel and polytetrafluoroethylene (PTFE) were used as opposite pairs, respectively, for their different wetting properties with FF. The experimental results show that compared with normal surface/PTFE frictional pair, the magnetic surface/PTFE couple expresses distinct friction increasing, while the magnetic surface/SUS316 steel pair presents obvious advantages of antifriction especially at high sliding speeds. The higher the surface magnetic flux is, the better is the tribological performance it displays especially at a higher sliding speed.

Tribological behavior of Ti3SiC2/(WC–10Co) composites prepared by spark plasma sintering

The dry sliding friction and wear behavior of Ti3SiC2/(WC–10Co) composites (TWCs) against GCr15 steel pair at room temperature was investigated through the determination of friction coefficient and wear rate under different conditions and the analysis of the morphologies and compositions of wear debris, worn surfaces of TWC and GCr15 steel. The friction coefficients of TWC with 3wt.% WC–10Co were in the range of 0.40–0.48, and the wear rate varied from 0.6×10−4mm3(Nm)−1 to 1×10−4mm3(Nm)−1. At the load of 10N and sliding speed of 0.353m/s, the glazes were formed on the worn surfaces of TWC. The wear mechanisms were complicated, including micro-cutting and abrasive wear of TWC, oxidation wear of GCr15 steel, as well as adhesive wear caused by the glaze flaking.

Strength and microstructure of laser fusion-welded Ti–SS dissimilar material pair

The ability to efficiently create robust and reliable dissimilar metal joints has the potential to enable new functionalities and reduce the manufacturing costs of medical devices. The need for dissimilar material welds in the medical device industry is driven by the unique properties exhibited by biocompatible materials such as stainless steel and titanium, as well as shape memory materials such as NiTi. Many material pairs, however, suffer from significant intermetallic phase formation during welding which greatly reduces their strength. This study investigates the microstructures and strength of the laser fusion-welded titanium–stainless steel dissimilar material pair as a simplified model of the NiTi–stainless steel pair. Compositional and structural analysis of the weld pool is performed and fracture morphologies are analyzed in different regions of the weld joint. The role of weld pool geometry, heat flow, and quench rate on the resultant phases, microstructures, and strength of the welds is discussed.

Effect of boronizing on the dry sliding wear behavior of DC53/0.45 mass% C steel pairs

The effect of single phase boride layer of DC53 steel disk on subsurface structure evolvement in the dry sliding friction-induced surface layer of 0.45 mass% C steel pin was investigated. Microstructure and microhardness of subsurface layers of 0.45 mass% C steel pin against unboronized and boronized DC53 steel discs after dry sliding friction test were studied by means of OM, SEM, TEM and microhardness tester. Results showed that boride layer significantly affected microstructure evolvement in worn surface layer of 0.45 mass% C steel and the three layers including substrate layer, plastic deformation layer and unpeeling delamination layer were formed beneath the worn surface of pin against the boronized disc, while only two layers except unpeeling delamination layer were formed against the unboronized disc. The microhardness of subsurface layer of 0.45 mass% C steel pin decreased as the depth beneath worn surface increased without regard to the unpeeling delamination layer in BD tribopair. The ferrite grains in the worn surface layer of pin for BD tribopair were ultra-fined, of which reason was considered to be the result of joint action of frictional heat and shear deformation.

Influence of Temperature and Reynolds Number on the Galvanic Corrosion of the Copper/AISI 304 Stainless Steel Pair in Lithium Bromide Using a Zero-Resistance Ammeter

The effects of temperature and Reynolds number (Re) on the galvanic corrosion of the copper (UNS C15710)/AISI 304 (UNS S30400) stainless steel pair in a concentrated lithium bromide (LiBr) solution was investigated in a hydraulic circuit using a zero-resistance ammeter. Results show that copper is the anode and that galvanic current density decreases with time because of the formation of a protective film. Initially, galvanic current density increases with Re; however, with time, differences decrease and this tendency is even reversed. As Re increases, greater quantities of corrosion products are initially produced and a thicker film is formed. The galvanic current density increases with temperature, suggesting that the films formed at lower temperatures are less defective and more resistant; however, at the highest flow rate, with time, the galvanic current density is lower at 75°C than at 50°C. This behavior is attributed to the quick and large formation of corrosion products at the highest flow and tem...

Thermogalvanic corrosion and galvanic effects of copper and AISI 316L stainless steel pairs in heavy LiBr brines under hydrodynamic conditions

Thermogalvanic corrosion of the copper/copper and AISI 316L/AISI 316L stainless steel pairs was studied in heavy lithium bromide brines under hydrodynamic conditions. The galvanic coupling effect between copper and stainless steel was also analysed. The cold electrode (25°C) was the stainless steel for the galvanic pair, whereas copper temperature varied (25, 50 and 75°C). A hydrodynamic circuit was designed to study thermogalvanic corrosion by means of the zero resistance ammeter technique. Hot cathodes take place in stainless steel pairs while cold cathodes are present in copper/copper and stainless steel/copper pairs; this agrees with the thermal temperature coefficient of the potential sign. Thermogalvanic corrosion increases corrosion rates, especially working with copper. Weight loss measurements show that there is a combined effect due to the thermogalvanic and the galvanic effects.

Preparation and Evaluation of Tribological Properties of Cu Nanoparticles Surface Modified by Tetradecyl Hydroxamic Acid

Oil-soluble Cu nanoparticles without phosphorus and sulphur elements were prepared using in situ surface-modification technique with hydrazine hydrate as a reductant and tetradecyl hydroxamic acid (THA) as a modifier. The phase composition, microstructure, and chemical structure of as-synthesized Cu nanoparticles (coded as THA-capped Cu or THA-capped nano-Cu) were analyzed by means of X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectrometry. The thermal stability of THA-capped Cu was examined using thermogravimetric analysis and differential thermal analysis. The antiwear ability of THA-capped Cu as an additive in liquid paraffin was examined using a four-ball machine, and the morphology of worn steel balls was examined using a scanning electron microscope, an energy dispersive spectrometer and an X-ray photoelectron spectroscopy. It has been found that THA-capped Cu can be well dispersed in some organic solvents. As-synthesized THA-capped Cu as an environmentally friendly additive in liquid paraffin shows excellent antiwear ability for the steel–steel contact. Besides, Cu nanoparticles are able to deposit and fill up micropits and grooves on steel sliding surfaces under a higher load and hence greatly reduced wear of the steel–steel pair thereat by way of self-repairing of worn surfaces of the steel–steel frictional pair, showing promising application as an environmentally acceptable lubricating oil additive.

The effect of temperature on sliding wear of steel-tool steel pairs

The need to reduce the use of lubricants and the increased use of high strength steels has resulted in increased wear of die materials employed in the sheet metal stamping industry. In this study, unlubricated sliding wear tests of mild carbon steel sliding on D2 tool steel were performed using a pin-on-disc tribometer to investigate the wear mechanisms relevant to stamping tools. Constant force and speed were applied while the sliding distance and temperature were varied to investigate the effect of temperature on the two paired steel materials. It was found that the wear mechanisms of D2 tool steel were temperature dependent, showing a significant transition in dominant mechanisms in the ambient to 150°C temperature range. Such wear behavior has not been reported in literature. An interesting aspect of this study is that material transfer between the tool and sheet can be minimized at a certain temperature range. Hence, the results of this study may be of economic importance to the automotive industry and influence the wear models employed for future tool wear analysis in sheet metal stamping.

High temperature tribological behaviour of tool steels during sliding against aluminium

Abstract Soldering and abrasive wear of die-casting tools are some of the biggest problems facing the aluminium die-casting industry. The understanding of the tribological behaviour is crucial to design new tool steels and tool steel-coating systems. The present study aims at investigating aluminium adhesion of aluminium/tool steel pair, performing sliding tests at high temperature with ball-on-disc configuration to reproduce solid/solid interaction. Different test conditions have been conducted in order to select the optimal test parameters to obtain aluminium adhesion on disc surface. Once the lab test has been designed, the high temperature tribological performance of different hot work tool steels (uncoated and coated by PVD) sliding against aluminium has been studied to allow proper die material design and selection.

Effects of Ag-Carried Content in P/Ag Nanocomposites on Tribological Properties of 45 Mild Steel Friction Pairs

In this paper, some Ag-carried palygorskite nanocomposites P/Ag were prepared, their silver content were 1.3%, 4.61%, 9.54% separately. To investigate the effects of the silver content on tribological properties of 45 mild steel pairs, the P/Ag carried different Ag content were used as lubricant additive and their tribological properties were tested on the MMU-10G testing machine. The wear mass loss is used to assess the anti-wear properties of different additives. The surface topographies and main elements are analyzed through SEM and EDS after running for 30 hours. The results show that the friction coefficient and the wear mass loss significantly decrease along with the increase of silver content in the P/Ag: the average friction coefficient of the P/Ag with 9.54% silver reduces about 65% as much as the one with 1.3% silver, meanwhile, the wear mass loss decreases 57% likewise. The surfaces after rubbing 30 hours, some kind of auto-restoration films that contains sort of characteristic elements such as O, Si, Mg, Al, Ag etc. are formed on the surfaces. With the help of this kind of films, the anti-wear properties of the friction pairs are finally improved. The factors that cause the improvement of anti-friction properties of the friction pairs lie in the quality and the silver content of the auto-restoration films formed on the surfaces of friction pairs.

Apparatus for high temperature friction measurement

Abstract The static and dynamic coefficient of friction between two flat surfaces at elevated temperature is under investigation. The equipment used in this study was originally designed for the precision glass molding (PGM) process and was then modified for friction measurement. The ultimate aim of this research is to study and characterize the frictional behavior between glass and a mold surface at elevated temperatures typical of the PGM process and under conditions similar to those for this process. This paper describes the design of the apparatus, and validation experiments using a steel–steel material pair at room temperature for comparison with values reported in the literature. The average friction coefficient between the steel–steel pair was found to be 0.17. Subsequent experiments using steel against steel and BK-7 glass against steel, found the stick-slip phenomena is happening at 577 °C.

Film Formation Property of Mineral Particles as Grease Lubricant Additives at Different Friction States

The characteristics of the 1045 steel pairs using superfine mineral powder as grease lubricant additive were investigated by an AMSLER friction and wear tester at different wear states. The surface topographies and composition of the worn surface of 1045 steel rings were identified by SEM and EDAX. The surface roughness of the samples was investigated by a profilometer. The results show that the additives can form a self-repairing film on the worn metal surface at Sliding state and there no film formed on the worn metal surface at Rolling-Sliding state. The reason is that the friction heat and friction energy produced by Sliding friction higher than the friction heat and friction energy produced by Rolling-Sliding friction.

Formation of surface layer with nanosize grain-subgrain structure due to friction of a copper – tool steel pair

The process of nanostructuring of a copper specimen in a friction pair with tool steel is studied. Diffraction analysis of the nanocrystalline layer formed due to friction on the surface of the specimen is performed. The mechanism of straining of the layer is associated with flow of viscous Newtonian fluid or of granulated medium.

High-temperature friction and wear characteristics of hardened ultra-high-strength boron steel

The usage of ultra-high-strength boron steel (UHSS) in automotive industry has increased rapidly in the recent past. Forming of UHSS components is performed at elevated temperatures, which also offers the possibility of hardening through quenching directly after forming. However, the influence of hardening on friction and wear during relative sliding between the tool and the workpiece is unclear. Therefore, the friction and wear characteristics at elevated temperatures of hardened and unhardened UHSS and tool steel pairs are investigated in this study. The results show that both friction and wear at all the investigated temperatures are affected by hardening of the UHSS. For uncoated UHSS, the hardening resulted in lower friction and the tool wear increased at low temperatures, but was not affected at elevated temperatures. This was attributed to the higher hardness after hardening combined with the presence of an oxide scale on the UHSS after heating and quenching. For Al—Si-coated UHSS, the hardening reduced friction and tool steel wear at elevated temperatures, and also reduced the wear of the Al—Si-coated high-strength steel at low temperature mainly owing to the formation of an intermetallic layer on the Al—Si-coated UHSS surface after exposure to elevated temperatures.

Anti-Wear Property of Self-Repairing Mineral Particles as Grease Lubricant Additives on the Metal Friction Pairs

The characteristics of the 1045 steel pairs using serpentine particles as grease lubricant additive were investigated by an AMSLER friction and wear tester. The surface topographies and composition of the worn surface of 1045 steel rings were identified by SEM and XPS. The results show that the additives can form a self-repairing film on the worn metal surface. It can reduce the abrasion of the friction pairs significantly. The main elemental compositions of the film are Fe, O, Si, C and Mg, which indicates that the additives directly take part in the formation of the self-repairing film.

Friction and wear of copper samples in the steady friction state

The effect of sliding velocity and load on the friction and wear of Cu–steel pairs was studied. Elasto-hydrodynamic (EHL), mixed (ML) and boundary lubrication (BL) regions were analyzed using the Stribeck curve. The lubrication number of Schipper, Z, was used in the analysis of the Stribeck curve. Steady friction states were observed in the mixed EHL and BL regions, however two types of the ML region are revealed. The first type is the stable ML range. The second one is the range of unstable friction and wear when a decrease of the lubricant film leads to abrupt change of all controlled parameters. It was found that a transition to the unstable ML region occurs within a narrow range of Z parameter. Wear modes in the lubrication regions were studied. Deformation hardening in the lubricant regimes is discussed.

Assessment of lubricity of compositions of fuel oil with biocomponents derived from rape-seed

This paper presents an assessment of tribological properties of compositions of fuel oil containing fatty acid methyl esters derived from rape-seed oil. An HFRR (high-frequency reciprocating rig – ball-on-flat) apparatus was used in this investigation. The studies were carried out for a steel–steel pair in the concentrated contact. The tribological properties were determined by motion resistances, wear and lubricant film concentration. The surfaces were analysed after tribological tests. The aim of the investigation was an attempt to obtain a correlation between wear quantities being measured and percentage content of bioadditives in fuel oil. It was found that at as little as 5% of the additive the coefficient of friction decreases by about 20% while wear decreases twofold relative to fuel oil, which may result from an increase in the stability of the lubricant film.

The influence of Reynolds number on the galvanic corrosion of the copper/AISI 304 pair in aqueous LiBr solutions

The influence of Reynolds number on the galvanic corrosion of the copper/AISI 304 stainless steel pair in a concentrated lithium bromide solution was investigated according to the mixed potential theory. A hydraulic circuit was designed to study dynamic corrosion processes in situ. A potential relation between corrosion current density ( i corr) and Reynolds number (Re) was found for copper, showing a mixed control of a chemical step and mass transport through the corrosion products film with the predominance of the former. No dependence of i corr on Re could be established for AISI 304, showing a chemical step control. Moreover, under stagnant conditions, partial passivation may occur in AISI 304; however, under flowing conditions passivation is not possible. Copper is the anodic element of the pair under all flowing conditions analysed. The galvanic phenomenon is more important as Re increases, but the results show compatibility of both materials at all Re values analysed. Similarly, a potential relation between galvanic current density ( i G) and Re was found, showing a mixed control of a chemical step and mass transport with the predominance of the latter. Copper corrosion resistance decreases more rapidly as Re increases due to the AISI 304 galvanic effect: there is a synergy between the galvanic effect and the hydrodynamic conditions. Under stagnant conditions, the galvanic behaviour of the materials is close to the compatibility limit and an inversion of the anodic element of the galvanic pair takes place.

Characterization of tribofilms derived from zinc dialkyldithiophosphate and salicylate detergents by X-ray absorbance near edge structure spectroscopy

Phosphorous and sulfur L- and K-edge X-ray absorption near edge structure (XANES) spectra were recorded to characterize the surface chemistry of the tribofilms derived from a commercial zinc dialkyldithiophosphate (ZDDP) and its blends with overbased calcium and magnesium salicylate detergents. The results show that the chemical structure of the tribofilms generated from the mixture of ZDDP and detergents is different from that of the tribofilm derived from ZDDP alone. However, the two kinds of detergents inhibit ZDDP from forming tribofilm, producing thinner polyphosphate films. Though XANES analysis does not provide definite evidence to the existence of magnesium element in the tribofilms, it is likely that calcium or magnesium has been incorporated therein. Moreover, ion exchange reaction and the formation of zinc polyphosphate film may occur simultaneously during sliding. However, calcium or magnesium (poly)phosphates do not contribute to reduce friction and wear of a steel–steel pair.