Variations in Wear Resistance of a Novel Triboalloy-Pseudoelastic TiNi Alloy - with Respect to its Pseudoelasticity and Hardness

It has recently been found that TiNi shape memory alloy has another attractive property: high resistance to wear. The wear resistance of this alloy benefits from its pseudoelasticity (PE). It has, however, been noticed that other mechanical properties also affect the wear resistance, especially the hardness. Research was conducted to investigate the correlation between the wear resistance and both the PE and hardness. It has been demonstrated that when the PE is high, lower hardness leads to higher wear resistance.     

Indentation behaviour and wear resistance of pseudoelastic Ti–Ni alloy

Abstract

Recent studies demonstrate that near equiatomic Ti–Ni alloys possess high resistance to surface damage by wear. It is suggested that the high wear resistance of Ti–Ni alloys is closely correlated to their pseudoelasticity, which is usually evaluated by tensile testing. However, when a Ti–Ni alloy is under wear, its surface is in a complex stress state. Since the thermoelastic martensitic transformation of Ti–Ni alloys responds differently to different stresses, it may not be appropriate to evaluate the pseudoelasticity by tensile testing. The present paper reports recent work on pseudoelastic behaviour of a Ti–51 at.-%Ni alloy employing a microindentation technique as well as tensile testing methods. In the present work, the wear performances of Ti–51 at.-%Ni alloy specimens with different degrees of pseudoelasticity were also investigated, and efforts were made to explain the beneficial effect of pseudoelasticity on the wear resistance of Ti–Ni alloys.     

New wear-resistant material: Nano-TiN/TiC/TiNi composite

Near-eqiatomic TiNi alloy has been found to exhibit high resistance to wear, especially to erosion. The high wear resistance of the alloy may largely benefit from its pseudoelasticity. Recent studies demonstrate that the wear resistance of TiNi alloy can be considerably enhanced when hard particles such as TiC were added as a reinforcing phase. It was expected that the wear resistance of such a composite could be further improved if the TiNi matrix can be strengthened with retained pseudoelasticity. Attempt was made to develop such a tribo composite, using nano-TiN powder to strengthen the matrix of the TiC/TiNi composite. The composite was made using a vacuum sintering process. Sliding wear behavior of this material was evaluated. It was demonstrated that the nano-TiN/TiC/TiNi composite exhibited excellent wear resistance, superior to those of the TiC/TiNi composite and WC/NiCrBSi hardfacing overlay. In order to understand the role of the nano-TiN powder, localized mechanical behavior and micro-scale wear of the TiNi matrix with and without nano-TiN powder were investigated using a triboscope. Worn surfaces were examined using SEM to better understand the wear mechanism and to find out clues for further development.     

Variations in Wear Resistance of a Novel Triboalloy Pseudoelastic TiNi Alloy-with Respect to its Pseudoelasticity and Hardness

It has recently been found that TiNt shape memory alloy has another attractive property, high resistance to wear. The wear resistance of this alloy benefits from its pseudoelasticity (PE). It has, however, been noticed that other mechanical properties also affect the wear resistance, especially the hardness. Research was conducted to investigate the correlation between the wear resistance and both the PE and hardness. It has been demonstrated that when the PE is high, lower hardness leads to higher wear resistance.     

Effects of electropulsing treatment on mechanical properties in Ti rich TiNi shape memory alloy

Abstract

The influence of electropulsing treatment on thermomechanical behaviour in terms of transformation temperatures and mechanical properties of a cold worked Ti rich TiNi shape memory alloy was studied. The results showed that the transformation temperatures increase with increasing current intensity. The superelasticity of the alloy is improved after the electropulsing treatment, and the hardness of the alloy decreased with increasing current intensity. The microstructure of the alloy showed that the above changes can be attributed to the decreasing dislocation density due to the current pulses.     

Effects of Yttrium Addition on Microstructure, Hardness and Resistance to Wear and Corrosive Wear of TiNi Alloy

TiNi alloy has a high resistance to wear and could be an excellent candidate for various tribological applications. In this paper, it was demonstrated that by addition of yttrium, hardness properties and resistance to wear and corrosive wear of TiNi alloy were improved. New yttrium rich regions were formed in microstructure of TiNi alloy. The improved properties of this alloy by the yttrium addition could be attributed to the formation of these regions. The results showed that there was an optimum content for addition of yttrium between 2% and 5% (in wt%), and above this content the improvement in properties of TiNi became minor.     

Development of novel wear-resistant materials: TiNi-based pseudoelastic tribomaterials

Extensive research has being conducted at the University of Alberta to investigate the wear behavior of pseudoelastic TiNi alloy during several wear processes, including erosion, corrosive erosion, and sliding wear. The research demonstrates that this novel wear-resistant alloy is multi-functional and could be an excellent candidate for various wear applications. Attempts have also been made to develop tribo-composites using the TiNi alloy as the matrix reinforced by hard ceramic particles. This paper presents a brief review of our recent progress in developing this novel tribo-material as well as in exploring the correlation between the pseudoelasticity and the wear resistance.     

Effects of Yttria Addition on Microstructure,Mechanical Properties,Wear Resistance and Corrosive Wear Resistance of TiNi Alloy

TiNi alloy has a high resistance to wear and could be an excellent candidate for various tribological applications. But studies show that oxygen active elements can improve properties of some alloys,markedly.Yttrium is one of the oxygen active elements.In this paper,the e-ects of yttria addition on properties of TiNi have been studied via micro-indentation,hardness,wear and corrosive wear tests.It is demonstrated that by addition of yttria to 5%,TiNi alloy can own improved mechanical properties and resistan...     

Laser surface alloying of case hardening steel with tungsten carbide and carbon

Abstract

The laser surface alloying process was used to introduce two different alloying materials, tungsten carbide (WC/Co) and carbon, into the molten surface of a case hardening steel (16MnCrS5), to improve its hardness and wear resistance. The chemical composition and the resulting microstructure in the alloyed layers were of particular interest in this investigation, because the strengthening mechanism was strongly dependent upon the type and amount of the alloy material. For laser alloying with carbon the increase in hardness and wear resistance was based on the martensitic transformation in the composition range concerned. For alloying with tungsten carbide it was necessary to consider two different strengthening mechanisms, namely, martensitic transformation and precipitation of carbides. In both cases the grain refinement in the laser affected zone had an additional effect. Resistance to dry abrasive sliding wear was measured using a conventional pin-on-disc wear testing machine. For both alloy materials the wear rate was substantially lower than that of a substrate that had been laser remelted without alloying additions.

MST/1556     

Wear behaviour of 85Al–10La–5Ni alloy prepared by powder metallurgy

Abstract

The dry wear behaviour of 85Al–10La–5Ni (at.-%) alloy hot pressed has been studied. The result shows that 85Al–10La–5Ni alloy possessed excellent wear resistance. The wear resistance of the alloy pressed at 773 K is three times as high as that of the A355 aluminium alloy. The fine high hardness intermetallic compounds contribute to the wear resistance of the alloy.     

Investigating the effect of quench environment and deep cryogenic treatment on the wear behavior of AZ91

Deep cryogenic heat treatment is a conventional supplementary treatment for steels to improve their wear resistance and hardness. Despite a variety of researches about steels, lack of investigation for the other alloys and materials is obvious. In this study, the effect of the deep cryogenic heat treatment and different quenching environments on the magnesium alloy (AZ91) was investigated via the optical microscope (OM), scanning electron microscope (SEM), hardness evaluation and wear test. For this purpose, the samples were solutionized at 420 °C for 24 h followed by quenching in different environments of water, air and liquid nitrogen. After that the samples were deep cryogenically treated in liquid nitrogen, followed by aging. Results show that deep cryogenic heat treatment improves the hardness and wear resistance. This behavior is a consequence of aluminum atoms jumping to the nearby defects, including dislocations. Moreover, it was clarified that increasing the cooling rate of quench environment improves the hardness after aging and that the predominant wear mechanism is abrasive.     

Wear properties of Ti–13Zr–13Nb (wt.%) near β titanium alloy containing 0.5 wt.% boron in dry condition,Hank's solution and bovine serum

The effect of heat treatment on the microstructure, hardness and sliding wear behaviour of Ti–13Zr–13Nb (wt.%) containing 0.5 wt.% B (TZNB) has been studied and compared with that of Ti–13Zr–13Nb (wt.%) (TZN) alloy. The wear properties were tested in dry condition and in simulated body fluid (Hank's solution and bovine serum) to understand the effect of different medium on wear behaviour of the TZNB alloy. Depending on the heat treatment condition the microstructure of the alloy consisted of α/martensite and TiB in β matrix. In general, the hardness of all the heat treated samples varied in a narrow range and in most of the cases addition of boron to the TZN alloy decreased the hardness. Almost all cases, no significant variation of the wear rate in dry condition with heat treatment was observed. Compared with the wear rate in dry condition, the wear rate in Hank's solution of the all the TZNB samples increased substantially. Moreover, the wear was found to be most severe in bovine serum. Addition of boron to TZN alloy did not result in any improvement in the wear resistance in all the media studied.     

Dry sliding wear of TiB2 particle reinforced aluminium alloy composites

Abstract

Al–4 wt-%Cu alloy and composites reinforced with 10 and 20 vol.-% of TiB₂ particles were prepared by powder metallurgy followed by hot isostatic pressing. The dry sliding wear behaviour of specimens of these materials was investigated. Pin-on-disc measurements showed that the wear resistance of Al–4Cu alloy can be improved dramatically by the addition of 20 vol.-%TiB₂ particles. This was due to the high hardness of the TiB₂ particles, and to strong particle–matrix bonding. The wear data were found to correlate with SEM observations.     

Tribological investigation of Zamak alloys reinforced with alumina (Al2O3) and fly ash

ABSTRACT

In this study, zinc aluminum alloy (Zamak) (ZA-27) composites reinforced by different weight fractions of fly ash, alumina (Al₂O₃), or both particles were produced using compo-casting technique. The composites were subjected to hardness and wear tests. The hardness of the composites increases with increase of the weight fractions of reinforcements. In wear test, the composites were examined under dry sliding conditions using pin on disc apparatus. The wear results revealed that the wear resistance increases with increase of the weight fractions of reinforcements. However, the effect of fly ash particles on the wear resistance of the produced composites is more statistically significant than the effect of Al₂O₃ particles. The morphology of the composites was examined using scanning electron microscopy (SEM) after the test. The SEM images revealed the existence of adhesion and delamination wear mechanism.     

Effect of secondary processing on the microstructure and wear behavior of spray formed Al–30Mg2Si–2Cu alloy

In the present work, Al–30Mg₂Si–2Cu alloy has been spray formed and subsequently hot pressed for densification. The alloy is then subjected to solutionizing and isothermal aging treatments. The microstructural features, hardness and wear behavior of spray formed and secondary processed alloys have been evaluated individually and compared with that of as-cast alloy. The microstructure of spray formed alloy showed refined and globular shaped primary Mg₂Si intermetallic particles and Al₂Cu precipitate particles uniformly distributed in Al matrix. The microstructure was refined further after hot consolidation. The microstructure after solution heat treatment appeared similar to that of the spray formed alloy but aging led to a further refinement in the microstructure compared to that of the hot pressed alloy. The evaluation of wear behavior of these alloys, under dry sliding condition, showed that the age hardened alloy exhibits maximum wear resistance and minimum coefficient of friction over the entire range of applied load (10–50 N) at a sliding speed of 2 ms⁻¹ followed by hot pressed, spray formed and solution heat treated alloys. The as-cast alloy showed the least wear resistance and highest coefficient of friction. Similar trend has been observed even in their hardness values too. The wear resistance of the alloys is discussed in light of their microstructural modifications induced during spray forming and subsequent secondary processing and also the topography of worn surfaces.     

On effect of squeezing pressure on microstructural characteristics,heat treatment response and electrical conductivity of an Al-Si-Mg-Ni-Cu alloy

Abstract

The effect of squeezing pressure on the heat treatment response and electrical conductivity of the cast alloy is not clear yet. The present research aims at investigating and elucidating them. It was found that the hardness peak occurred earlier for the pressurised cast alloy during the aging process as compared with non-pressurised one. Squeezing pressure reduces the time required for heat treatment. This significant fact was ignored by most researchers. Pressure also improved the electrical conductivity of the cast alloy. The results showed that the electrical conductivity of samples increases with increasing the aging time and temperature. Moreover, better mechanical properties including high hardness and ultimate tensile strength and good toughness and ductility of the pressurised cast samples indicate that these samples are more reliable to be used for different applications.     

Evaluation of effect of chromium on wear performance of high manganese steel

Abstract

The effects of elements such as Ni, Mo, Cr, Cu, and V on the wear behaviour of high manganese steels have been reported extensively. Most researchers agree on the influence of many of the elements but disagree on the effect of Cr. A study has been conducted to evaluate the effect of 1.7 and 2.3 wt-Cr on high manganese steel when subjected to various wear conditions: impact loading, abrasion, combined impact-abrasion, and combined abrasion-corrosion. The study has revealed that adding Cr to high manganese steel resulted in an increase in hardness and hardenability, and a decrease in toughness. The effect on wear resistance was found to depend on the wear conditions. Chromium alloyed high manganese steels showed superior wear resistance compared with plain Hadfield steels where corrosion, abrasion, and combined impact-abrasion conditions prevailed. Such conditions required a high surface hardness. Plain Hadfield steel showed superior wear resistance in conditions where pure impact wear is encountered. Such conditions required an increase in toughness rather than surface hardness.     

Martensitic transformation and work hardening of metastable austenite induced by abrasion in austenitic Fe-C-Cr-Mn-B Alloy - a TEM study

Abstract

The martensite transformation and work hardening of metastable austenite induced by abrasive wear in an austenitic Fe-C-Cr-Mn-B alloy were studied by TEM. The results show that an α' martensitic transformation occurred to form an elongated and equiaxial cellular dislocation substructure and the untransformed austenite matrix produced an equiaxial cellular dislocation substructure on the abraded surface. Electron diffraction patterns of the abraded material are composed of diffraction rings with series of broken arcs resulting from a fine grain structure and the deformation texture. The work hardening zone of austenite at the subsurface reveals heavy slip bands and deformation faults, at which the dislocations pile up. Examples of ? martensite induced by abrasive wear can be detected. The α' martensite transformation and metastable austenite work hardening should bring about an increase in surface hardness and wear resistance. Additionally, the cellular dislocation substructure of α' and γ have a significant effect on increasing the hardness of the wear surface. Observation by TEM indicates that the α' martensite transformation happens more easily in the austenite matrix near the carbide (Fe, Cr)₇C₃ as a result of the depletion of carbon and chromium.     

Influence of minor additions on characteristics of Cu–Al–Ni alloy

Abstract

The aluminium and nickel contents of Cu–Al–Ni alloy are varied to relate the parent phase chemistry to its shape memory behaviour. Rare earth and grain refining elements (titanium, zirconium, boron, etc.) are added in minor quantities to assess their effects on the grain refinement of the alloy and also on its shape recovery behaviour. It is observed that increasing the aluminium and nickel contents decreases the shape recovery temperature whereas minor additions are found to increase it. The alloys have been aged in the parent as well as the martensitic phase to investigate the influence of minor additions on their aging response. It is observed that precipitation of γ₂ phase occurs during the initial stage of aging of the ternary alloy. The aging behaviour is monitored via changes in resistivity and hardness of the alloys during aging. Minor additions are found to retard the precipitation of γ₂ phase during aging. Titanium and rare earths particularly reduce the tendency for grain coarsening in the alloy. It is further observed that two types of martensite, β′₁ and γ′₁, are produced in the alloys under investigation. The transformation temperatures of these martensites are also related to the aluminium content of the alloy.

MST/1744     

Effect of thermomechanical treatment on spray formed Cu – Ni – Si alloy

Abstract

The heat treatment response of a spray formed Cu – 2.4Ni – 0.6Si (wt-%) alloy has been investigated. The spray formed alloy was given various thermomechanical treatments prior to isothermal aging. These treatments included solutionising and/or cold rolling with different reductions in original thickness. The variation in hardness and electrical conductivity of the alloys was measured as a function of the aging time. The results indicated the highest peak hardness value of ~250 kg mm^-2 for the alloy aged after solution treatment and cold rolling to 40% reduction in thickness, compared with the maximum hardness of 220 kg mm^-2 for specimens aged directly in the as spray formed condition. However, the electrical conductivity after aging was observed to be a maximum of 65%IACS (International Annealed Copper Standard) in specimens cold rolled to 80% reduction in thickness before aging. The aging response was observed to accelerate with the degree of cold working. Optical, scanning electron and transmission electron microscopy were used for microstructural characterisation of the materials. Precipitation of the second phase was observed to dominate in deformation bands. The alloy showed evidence of discontinuous precipitation, particularly when the alloys were cold rolled before aging. The onset of discontinuous precipitation led to a drastic deterioration in hardness of the alloys. The precipitation behaviour of the alloy is discussed in the light of microstructural characteristics associated with various processing conditions of the alloy.