The poor mechanical properties are the main obstacle for the present solid-lubricating bulk materials in practical applications. In this work, the microstructure and high temperature mechanical properties of the solid-lubricating NiCrMoAl–12.5 wt%Ag–xCaF2/BaF2 eutectic (x=5 or 10 wt%) composites, denoted as the 5 F and 10 F respectively, have been evaluated. Both the composites display superior tensile strength of above 300 MPa from room temperature (RT) to 600 °C and extraordinary compressive strength that is above 500 MPa at 800 °C. These superior properties make the composite particularly suitable for bearing applications where the compression strength is an engineering factor to be preferably considered.

•The Ni-alloy matrix composite with Ag, BaF2/CaF2 and graphite were prepared.•The tribological properties were investigated in air from RT to 800 °C.•The effect of amount of graphite on the COF and wear rate is obvious.•The COF and wear rate were dependent on the testing temperature.•The oxidation plays an important role to wear behavior of the composite.Solid lubricant materials are promising for high performance machines and mechanical systems. In this paper, the nickel alloy matrix solid lubricant composites containing Ag, BaF2/CaF2 and three different amounts of graphite were prepared by hot pressed sintering method. The tribotests were performed sliding against Si3N4 ball in air from room temperature to 800 °C. The effect of graphite content on the tribological behavior of the composites under high temperatures was studied. Micro-Raman, XRD and SEM analysis were used to analyze the morphologies and chemical composition of the worn surface and the wear mechanisms were also discussed.

•TiAl alloy exhibits excellent corrosion resistance in sea water.•The tribological behavior in sea water depends on the properties of tribo-pairs.•There are distinct wear mechanisms for TiAl alloy mated with different couple balls.In order to evaluate the potential of the new light-weight structural TiAl alloy for marine application, the electrochemical corrosion and tribological behavior of TiAl alloy in a sea water environment have been investigated in this paper. A commercial Al 5083 marine product was selected as the control tests. The counterface materials include SiC, GCr15 steel and Hastelloy C276 alloy. TiAl alloy exhibits excellent corrosion resistance over Al 5083 alloy in sea water. The wear behavior of the two materials in sea water is sensitive to counterface materials. With GCr15 steel and C276 alloy as the mating surfaces, the wear resistance of TiAl alloy is significantly superior to that of Al 5083 alloy in sea water.

In this article, the dry-sliding tribological behaviors of TiAl-based composites reinforced with 20 and 40 vol% in situ synthesized TiB2 produced by a hot-press sintering process were investigated from room temperature (RT) to 800 °C. The results show that the high-temperature wear resistance of the TiAl alloy is improved by adding the TiB2 particles under all the testing temperatures, and the more the TiB2 reinforcement, the better the wear resistance is. This improvement is more significant at 600 °C and above, especially for the composite with 40 vol% TiB2, whose wear rate is 4–10 times lower than TiAl at 600 and 800 °C. Accordingly, the wear mechanisms transfer from abrasion wear at low and moderate temperature (RT, 200 and 400 °C) to oxidation wear at high temperature (600 and 800 °C). In addition to the brittle-to-ductile transition of the materials and oxide layer formation, the phase transition of Al2O3 and TiO2 may be partly responsible for the promising wear resistance at high temperatures.

•Fe3Al–Ba0.25Sr0.75SO4 exhibits excellent high temperature tribological properties.•The wear of Fe3Al–30 wt% Ba0.25Sr0.75SO4 is an order of magnitude lower than Fe3Al.•The COF of Fe3Al–30 wt% Ba0.25Sr0.75SO4 is 3 times lower than Fe3Al above 600 °C.•The good tribological properties of the composite are due to the lubricating film.Self-lubricating materials are particularly suitable used in the advanced mechanical motion systems with extreme conditions such as high temperature, high-speed and heavy-loading. In this paper, a high-temperature self-lubricating composite, Fe3Al with embedded Ba0.25Sr0.75SO4 solid lubricant are prepared by hot-pressed sintering technique. Meanwhile, the effects of Ba0.25Sr0.75SO4 fraction on microstructure, hardness and high-temperature tribological properties of the composites are investigated. The results show that the high-temperature tribological properties of the Fe3Al alloy are greatly improved by the addition of Ba0.25Sr0.75SO4, and the wear mechanism transforms from fatigue wear to abrasion wear.

•Ti3AlC2/SiC tribo-pair showed excellent tribological properties in sea water environment.•The friction coefficient and wear rate decreased with reciprocating frequency increasing.•A layer of soft hydrated tribo-film can be formed because of tribo-chemical reaction.•The tribo-film can be easily sheared and provide favorable lubrication.In this paper, the tribological property of Ti3AlC2/SiC tribo-pair in sea water was investigated. For comparison, the tribological property in deionized water was studied as well. The results revealed that the Ti3AlC2/SiC tribo-pair displayed better lubricating effect in the two aqueous liquids. The friction coefficient and wear rate decreased with the increment of reciprocating frequency. Herein, a layer of soft hydrated tribo-film, which was caused by tribo-chemical reaction in aqueous environment, was easily sheared and conceived to be liable for the lubricating effect. The lubrication and wear mechanism were boundary lubrication and tribo-chemical wear, respectively. When the soft hydrated tribo-film was exposed in air, the tribo-film could contract and yield rimose tribo-film on account of the loss of water.

•High purity AlMgB14 powder was synthesized successfully.•Cupper matrix gets strengthened by doping moderate amount of AlMgB14.•The sintering temperature exerts a significant effect on properties of Cu/AlMgB14.•Cu/AlMgB14 composite shows a lower dry friction coefficient, as low as 0.2.Cu/AlMgB14 composites with different AlMgB14 amounts were fabricated by hot press sintering. The influences of the sintering temperature and the AlMgB14 content on the tribological and mechanical properties of the composites were preliminarily investigated. In short, a lower sintering temperature leads to a lower friction coefficient but relatively poor mechanical properties, while the opposite results are shown at higher sintering temperature. Besides, raising the AlMgB14 concentration to some extent can markedly reduce the friction coefficient and the wear rate of the composites. Especially when sintered at lower temperature, the composites with 10 wt% AlMgB14 or above have the lowest friction coefficient of 0.2.

•Tribological behavior of a Ni-based solid lubricating composite was studied.•Effect of sliding speed and testing temperature on the behavior is investigated.•Tribological behavior is high dependent on sliding speed and temperature.•The composite exhibits favorable self-lubricity at 0.2–1.0 m/s and RT-800 °C.•The oxide layer plays an important role to wear behavior at high temperatures.High temperature solid lubricating materials show important demands in applications for moving machine assemblies under extreme operating conditions. In this study, the tribological behavior of a nickel-alloy based self-lubricating composite (82.5%nickel-alloy–12.5%Ag–5%BaF2/CaF2) against Si3N4 ball was evaluated under various temperatures and sliding speeds. Results showed that the friction coefficient and wear rate of the composite were greatly dependent on testing temperature and sliding speed. The composite exhibited favorable lubricity in the wide temperature range from 25 °C to 800 °C. The friction and wear mechanisms were explored by observing and analyzing the worn surfaces.

•The nickel-alloy-based solid-lubricating composites are prepared.•The composites show favorable tribological properties from room temperature to 900 °C.•The effect of amount of BaF2/CaF2 eutectic on the CoF is small, but it is obvious on the wear.•The friction coefficient is slightly lower as sliding against Si3N4 than Inconel 718.•The wear rate is nearly independent of the counterfaces of Si3N4 and Inconel 718.High-temperature self-lubricating nickel-alloy based composites with Ag and three amounts of BaF2/CaF2 eutectic were prepared by hot press sintering technique. Both the composites with 5 wt% and 10 wt% BaF2/CaF2 eutectic exhibited markedly higher strength than 15 wt% composite. The friction coefficient of the three composites was comparable. All three composites showed the highest wear rate at 600 °C, but very lower at 800 and 900 °C. The friction coefficient of the three composites was slightly lower as sliding against Si3N4 than Inconel 718. The friction and wear mechanism was proposed.

In this paper, Cu/AlMgB14 composites with by weight percent, 5, 10 and 20 % of the AlMgB14 (referred to CA-5, CA-10 and CA-20) were fabricated by hot-press sintering method. The mechanical and dry-sliding tribological properties of the three composites were investigated. The results indicated that the densities of the Cu/AlMgB14 composites were lower than copper, whereas the hardness higher. The friction and wear behaviors of the composites were strongly dependent on the AlMgB14 content. The friction coefficient was in the range of 0.73–1.0 for CA-5, but it was always steady at about 0.2 for CA-10 and CA-20. Accordingly, the increase in the AlMgB14 concentration can improve the wear resistance of the composites.

The microstructure, mechanical and dry-sliding tribological properties of TiAl-based composites with 20 and 40 vol% in situ formed Ti2AlC, produced by hot press sintering process, are investigated. The microstructural characterization reveals that Ti2AlC phase is in the form of spherical particles and large blocks, and the quantity of the blocks increases with Ti2AlC content. This difference in the morphology and distribution of the Ti2AlC phase leads to the discrepancy of the wear resistance of the composites. In contrast to the Ti-46Al-2Cr-2Nb intermetallics, the dry-sliding wear resistance of the TiAl/Ti2AlC composites first declines slightly and then enhances with the Ti2AlC content. Furthermore, the TiAl/40 % Ti2AlC composite shows low wear rate at higher sliding speed.

The dry-sliding tribological behaviors of Ti–46Al–2Cr–2Nb intermetallics and its composites with 20 and 40 vol% in situ formed TiB2 produced by hot press sintering process were investigated. Also, the microstructures and mechanical properties of the three materials were examined. With the increase of TiB2 amount, the hardness and wear resistance ascended. The enhanced wear resistance can be attributed to the higher hardness and the load-carrying role of TiB2. The friction coefficient was irrespective of TiB2 content. The wear mechanism of the materials was dominated by fatigue wear and delamination.Highlights► TiB2 enhanced significantly wear-resistance of the Ti–46Al–2Cr–2 Nb intermetallics. ► The friction coefficient of the materials is irrespective of TiB2 content. ► Wear resistance significantly increases with rising TiB2 amount.

The high-temperature tribological behaviour of Fe–28Al–5Cr alloy and its composites containing TiC was investigated against a Si3N4 ceramic from 25 to 800 °C. The high-temperature wear resistance of the materials was significantly improved by the addition of TiC, which was attributed to the high hardness of the composites, as well as the support role of hard TiC. The oxidation played an important role to friction and wear.Highlights► TiC improves wear-resistance of Fe–28Al–5Cr alloy at high temperature obviously. ► Wear rate of the composite with 50% TiC is 28–35 times lower than that of Fe–28Al–5Cr alloy. ► Enhanced wear-resistance of composites originates from high hardness and high strength. ► At 200–800 °C, the oxides play an important role in friction process. ► Wear resistance significantly increases with rising TiC amount.

•TiC improves obviously the wear-resistance of Fe–28Al–5Cr alloy at H2SO4 solution.•Wear rate of the composite with 50% TiC is 4–38 times lower than that of Fe–28Al–5Cr alloy.•The reasons for low friction coefficients are due to the formation of FeS and hydrated silica.•Wear resistance significantly increases with rising TiC amount.Sliding wear behaviour of Fe–28Al–5Cr and its composites containing 15, 25, 35 and 50 wt% TiC was investigated against a Si3N4 ceramic ball in 1 mol/L H2SO4 solution. The wear rate and friction coefficient were significantly reduced by the addition of TiC. The main reason should be the load carrying role of hard TiC and the formed FeS and hydrated silica films becoming more and more stable with TiC content. The dominant wear mechanism of the Fe–28Al–5Cr alloy and the 15% composite is ploughing and corrosive wear, but that of the 25%, 35% and 50% composites is corrosive wear.

In this paper, we reported the tribological behavior of Ti3AlC2 disk sliding against SiC ball from room temperature (RT) to 1,000 °C. The tribological properties are highly dependent of testing temperature. At RT, the coefficient of friction (CoF) is as low as 0.34 in the steady state, but the wear rate is relative high (4.26 × 10−4 mm3/Nm). At 200 and 400 °C, the CoF is as high as 1.21, and the wear rates are very high, about on the order of 10−3 mm3/Nm. From 600 to 1,000 °C, however, Ti3AlC2 exhibits quite low wear rate on the order of 10−6 mm3/Nm and relative moderate CoF, 0.60–0.80. The compacted continuous oxide layer at 600 °C and above might be responsible for the outstanding wear resistance.

In this study, we report that a layered Ti3AlC2 ceramic exhibited three distinct tribological behaviors at different vacuum degrees. It is firstly found that the layered Ti3AlC2 exhibited intrinsic self-lubricity under vacuum degree from 2.0×104 to 5 Pa with the coefficient of friction (CoF) as low as 0.2 and nearly no wear. Under lower 0.1 Pa and air atmosphere, however, it showed lubrication failure. Under lower 0.1 Pa, The CoF abruptly rose after transitory low friction in initial duration and deteriorated wear occurred in the Ti3AlC2. The CoF sluggishly ascended to stable value from 0.2 to 0.7 in air. The lubricating mechanism of Ti3AlC2 ceramic was proposed.

It is a challenge to design self-lubricating materials that exhibit and maintain reduced friction coefficient as well as high strength over a wide range of temperatures. A high-temperature self-lubricating nickel-alloy-based composite was created using the hot pressing technique. The composite exhibited high relative density, and simultaneously superior lubricating properties, average friction coefficient below 0.25 from room temperature to 800 °C, and high strength, 470 MPa of tensile strength and 1500 MPa of compressive strength. The composite was very promising in high-temperature tribology.

A high-strength Fe85Ni15 alloy with lath martensitic structure was obtained by the self-propagating high-temperature synthesis technique. After tempering at 500 °C for 2 h, the hardness increased from 3.8 to 5.1 GPa, and the compression yield strength increased from about 1100 to 1500 MPa without much sacrifice of ductility. The strengthening effect might be attributed to the evolution of lath martensitic morphology and the reverse martensitic transformation.

The paper reports the dry-sliding tribological behavior of Fe100−x–Nix (x=20,23,25,30) alloys with various martensite fractions. For all the alloys, the friction coefficient decreased with increasing applied load and increased with increasing sliding speed, but there was nearly no difference between the different alloys. The wear rate of the alloys increased with increasing applied load and decreased slightly with increasing sliding speed. Microstructures had great influence on the wear behavior of these alloys. The Fe77Ni23 alloy with well-proportioned martensite exhibited the best wear resistance.Highlights► Different nickel contents lead to different martensite fractions in Fe–Ni alloys. ► Different phase compositions result in different mechanical properties. ► Phase compositions have little effect on friction coefficient of Fe–Ni alloys. ► Fe77Ni23 alloy with well-proportioned martensite phase exhibits the best wear resistance.

Tribological behavior of a Ti-46Al-2Cr-2Nb alloy, produced by hot-pressed sintering, was investigated using a home-built ball-on-disc tribotester against a Si3N4 ceramic ball at a constant speed of 0.188 m s−1 and an applied load of 10 N from 20 to 900 °C. It was found that the friction coefficient decreased slowly with increasing temperature from 20 to 600 °C, and then rose and reached the highest value at 800 °C, but slightly dropped at 900 °C. The wear rate of the alloy, in the magnitude of 10−4 mm3/Nm, increased mildly with increasing temperature to a maximum value at 400 °C and then dropped rapidly from 600 to 800 °C, and increased a little at 900 °C. The wear mechanism of the alloy transformed from mainly ploughing and small delamination wear at 20–700 °C to plastic deformation and adhesive wear at 800 and 900 °C. The transition of the wear mechanism occurred between 700 and 750 °C. The friction and wear behavior of the hot-pressed Ti-46Al-2Cr-2Nb alloy was comparable to that of a vacuum casting Ti-41.7Al-8.3Nb-0.09Y alloy measured under the same conditions for comparative purposes.Highlights► The tribological behavior of the Ti-46Al-2Cr-2Nb alloy was studied from 20 to 900 °C. ► The friction coefficient first decreases and then increases with the temperature. ► The wear rate of the alloy was strongly dependent on the test temperatures. ► There are two kinds of different wear mechanisms at below and above 750 °C.

The tribological behavior of a Ti-46Al-2Cr-2Nb alloy prepared by hot-pressed sintering was investigated under liquid paraffine lubrication against AISI 52100 steel ball in ambient environment and at varying loads and sliding speeds. For comparison, the tribological behavior of a common Ti-6Al-4V alloy was also examined under the same testing conditions. The worn surfaces of the two alloys were analyzed using a scanning electron microscope. The friction coefficient of the Ti-46Al-2Cr-2Nb alloy in the range of 0.13–0.18 was significantly lower than that of the Ti-6Al-4V alloy (0.4–0.5), but comparable to that under dry sliding, which indicated that TiAl intermetallics could be more effectively lubricated by liquid paraffine than titanium alloys. Applied load and sliding speed have little effect on the friction coefficient of the Ti-46Al-2Cr-2Nb alloy. The wear rate of the Ti-46Al-2Cr-2Nb alloy was about 45–120 times lower than that of Ti-6Al-4V alloy owing to Ti-6Al-4V alloy could not be lubricated effectively. The wear rate of the Ti-46Al-2Cr-2Nb alloy increased with increasing applied load, but decreased slightly at first and then increased with increasing sliding speed. The wear mechanism of the Ti-46Al-2Cr-2Nb intermetallics under liquid paraffine lubrication was dominated by main plowing and slight flaking-off, but that of the Ti-6Al-4V alloy was plastic deformation and severe delamination.

The tribological behaviour of Fe–28Al–5Cr and its composites containing 15, 25 and 50 wt% TiC (corresponding to 19.3, 31.2 and 57.6 vol%), produced by hot-pressing process, was investigated under liquid paraffine lubrication against an AISI 52100 steel ball in ambient environment at varied applied loads and sliding speeds. It was found that the wear resistance increased and friction coefficient decreased with increasing of TiC content. The coefficients of friction are in the range of 0.09–0.14 at the given testing conditions. The wear rates of all the materials except the 50% composite are on the order of 10−6–10−5 mm3 m−1, the wear rate for the 50% composite is too low to quantify under the two sliding conditions, (50 N, 0.04 m/s) and (100 N, 0.02 m/s). The wear rates of all the materials increase as applied load increases and the increasing extent diminishes with the increase of TiC content, but first increase slightly and then nearly remains steadiness with increasing sliding speed. The 50 wt% composite has wear resistance about 7–20 times better than pure Fe–28Al–5Cr at different sliding parameters. The enhanced wear resistance by TiC addition is attributed to the high hardness of the composites, as well as support of the oil lubrication film/layer by the hard TiC phase. The worn surfaces of all the materials are analyzed by a scanning electron microscope. The dominant wear mechanism of the Fe–28Al–5Cr and 15% composite is grooving and flaking-off, but those of the 25 and 50% composites are mainly shallow grooving.

The mechanical properties and wear behavior of an Fe70Ni30 alloy with twinned martensite structure obtained by deep cryogenic treatment at −196°c (DCT) were evaluated in comparison with that of coarse-grained (CG) Fe70Ni30 alloy (single austenite phase). The results showed that after the introduction of martensite with nano-scale twins, the Vickers hardness of Fe70Ni30 increased from 145 to 248 Hv. The friction coefficient of both samples was almost the same, and it decreased with increasing applied load and increased with increasing sliding speed. The XPS results indicated that oxide protecting film was formed on the worn surface, which may dominate the friction coefficient. The wear rate for both samples increased with increasing applied load and decreased slightly with increasing sliding speed. The wear resistance of DCT-Fe70Ni30 alloy was obviously enhanced. The wear mechanisms were investigated by SEM accordingly.Highlights► Nano-twinned martensitic structure was introduced in Fe70Ni30 alloy. ► Hardness and yield strength increased by introduction of nano-twinned martensite. ► The friction coefficient was not affected by the nano-twinned structure. ► Wear resistance of the nano-twinned Fe70Ni30 alloy enhanced obviously.

Dry-sliding tribological performance of the Fe–28Al–5Cr and its composites containing 15, 25, 35, 50 wt.% TiC, produced by hot-pressing process, was investigated against an AISI 52100 steel ball in ambient environment at varying applied load and sliding speed. It can be found that the coefficient of friction (COF) is irrespective of TiC content and applied load, but increases from 0.46 to 0.60 with increasing sliding speed at the given testing conditions. The wear-resistance increases with an increase of TiC contents. Impressively when TiC amount reaches 50 wt.%, the wear-resistance improves about 4–30 times compared to the pure Fe–28Al–5Cr at different sliding parameters. The wear rates of all the materials increase mildly with an increase in applied load, but are nearly independent of the sliding speed at an applied load of 20 N. The wear rates of the all materials are on the order of 10−3–10−4 mm3 m−1. In a word, the addition of the TiC can improve significantly the dry-sliding wear-resistance of the Fe–28Al–5Cr intermetallics at room temperature. The enhanced wear-resistance is attributed to the high hardness of the composites and as well hard TiC phase play a role of load-carrying. Worn surface features of all the materials were examined using a scanning electron microscopy (SEM). The dominant wear mechanism of Fe–28Al–5Cr and 15% composite was flaking-off, but those of 25–50% composites was flaking-off and plowing.Highlights► TiC improves significantly the dry-sliding wear-resistance of Fe-28Al-5Cr alloy. ► Wear rate of the composite with 50% TiC is 4-30 times lower than the pure Fe-28Al-5Cr alloy. ► Enhanced wear-resistance of below 15% TiC composites is attributed to high hardness. ► Enhanced wear-resistance of over 25% TiC composites originates from load-carrying role of TiC.

A simple and inexpensive method for combustion synthesis of the series of Fe-x%Ni martensite alloys (x = 15, 20, 23, 25 at %) was developed. XRD, SEM, and TEM examinations showed that all the products were composed of lath martensite and retained austenite. With increasing nickel content, the hardness and yield strength decreased gradually, which originated from the differences in phase compositions and micro structural characteristics. All the products exhibited high strength and good ductility, especially the Fe-15%Ni alloy which exhibited (in compression tests) high yield strength (up to 1300 MPa) at a good ductility (∼30%).

The tribological properties of the nano-eutectic Fe1.87C0.13 alloy are investigated under dry-sliding against AISI52100 steel ball in ambient environment with varying applied load and sliding speed. As comparison, the tribological properties of the same alloy after annealing treatment, which is with coarse-grained microstructure, also are examined at the same testing condition. The worn surfaces of the alloys are analyzed by a scanning electron microscope (SEM). The wear resistance of the nano-eutectic Fe1.87C0.13 alloy is about 2–6 times higher than that of the annealed coarse-grained Fe1.87C0.13 alloy, and the wear rates increase with increasing applied load and sliding speed. Friction coefficients of the two alloys are almost same. These results demonstrate that the wear resistance of the Fe1.87C0.13 alloy is improved by forming nanostructure to obtain enhanced mechanical properties, but the friction coefficient is not significantly affected owing to almost the same friction surface states. The wear mechanism of the two alloys shows slight difference.

The tribological properties of a Fe3Al material in an aqueous solution of 1 mol/l H2SO4 corrosive environment sliding against a Si3N4 ceramic ball are studied using an Optimol SRV oscillating friction and wear tester in a ball-on-disc contact configuration. We investigate the effects of load and sliding speed on tribological properties of the Fe3Al material. The worn surfaces of the Fe3Al material are examined by a scanning electron microscope (SEM) and an X-ray photoelectron spectroscope (XPS). It is found that the Fe3Al material exhibits better wear resistance than 1Cr18Ni9Ti stainless steel in the sulfuric acid corrosive environment. The wear rate of the Fe3Al material is on the order of 10−13 m3/m and increases with increasing load, but does not vary below the sliding speed of 0.08 m/s then dramatically increases with increasing sliding speed. The friction coefficient of the Fe3Al material is in the range of 0.1–0.28, and slightly increases with increasing load, and does not vary with the increase of sliding speed. The Fe3Al material occurs tribochemical reaction with the H2SO4 aqueous solution in the friction process. Wear mechanism of the Fe3Al material is dominated by microploughing and corrosive wear.

The tribological properties of the nano-eutectic Fe1.87C0.13 alloy are investigated under liquid paraffine lubrication against AISI52100 steel ball at room temperature with varied applied load and sliding speed. As comparison, the annealed coarse-grained Fe1.87C0.13 alloy is also examined in the same testing condition. The wear rate of the two alloys increases with increasing applied load and sliding speed. The wear resistance of the nano-eutectic Fe1.87C0.13 alloy is about 2–20 times higher than that of the annealed Fe1.87C0.13 alloy at present experimental conditions. The friction coefficients of the two alloys are almost same. The annealed Fe1.87C0.13 alloy shows serious wear under high applied load and sliding speed. The worn surfaces of the two alloys are analyzed by a scanning electron microscope. With increase in the applied load and sliding speed, the wear mechanism of the nano-eutectic Fe1.87C0.13 alloy is transformed from plowing to fatigue flaking pits, whereas that of the annealed coarse-grained Fe1.87C0.13 alloy is transformed from plowing to fatigue flaking pits then to severe fatigue wear.

Tribological properties of a nano-eutectic Fe1.87C0.13 alloy were investigated under distilled-water lubrication against AISI52100 steel ball for various applied loads and sliding speeds. For comparison, the tribological behavior of annealed coarse-grained Fe1.87C0.13 alloy was also examined under the same testing conditions. Worn surfaces of both alloys were analyzed by using a scanning electron microscope (SEM). The wear rate of nano-eutectic Fe1.87C0.13 alloy was on the order of 10−5 mm3/m. The wear rate of nano-eutectic Fe1.87C0.13 alloy was higher than that of annealed Fe1.87C0.13 alloy at lower load, but lower under higher load. The friction coefficients of the two alloys were similar and exhibited a slight increase with increasing sliding speed, but a small decrease with increasing applied load. The wear mechanism of the nano-eutectic Fe1.87C0.13 alloy was transformed from plowing and corrosion wear to slight fatigue cracking with increasing applied load, whereas that of the annealed coarse-grained Fe1.87C0.13 alloy was transformed from plowing and corrosion wear to severe fatigue flaking.

A bulk immiscible nanostructured Fe60Cu40 (ratio of atom) alloy is fabricated by a combustion synthesis combining rapid solidification technique that is convenient, inexpensive and capable of being scaled up for tailoring the bulk nanostructured materials. The Fe60Cu40 alloy is composed of dendrites (Fe(Cu) solid solution) with size of a few micron and matrix (Cu(Fe) solid solution) with size of about 30 nm. Owing to large superheat and rapid solidification process, there is no large-scale macroscopical separation in the Fe60Cu40 alloy.

This paper reports the tribological performance of the nano-eutectic Fe83B17 alloy under dry sliding against Si3N4 ceramic ball in ambient environment with varying applied loads and sliding speeds. Worn surfaces of the nano-eutectic Fe83B17 alloy were examined with a scanning electron microscope (SEM) and an X-ray energy dispersive spectroscope (EDS). The wear debris of the samples were also analyzed by X-ray diffractometer (XRD). The wear rate of the nano-eutectic Fe83B17 alloy was of the magnitude of 10−4 mm3/m, which was lower than that of the coarse grained Fe83B17 alloy. The friction coefficient of the nano-eutectic Fe83B17 alloy was almost the same as that of the coarse grained Fe83B17 alloy. The Fe2SiO4 oxide layer was formed on the worn surface of the nano-eutectic Fe83B17 alloy. However, on the worn surface of the coarse grained Fe83B17 alloy was found only a little Fe2SiO4. These results demonstrated that the nanostructure improved the wear resistance of the Fe83B17 alloy, but did not significantly affect the friction coefficient. The wear mechanism of the nano-eutectic Fe83B17 alloy was delamination abrasion mainly.

We have successfully synthesized bulk nanostructured Fe94.3B5.7 alloy using the one-step approach of a self-propagating high temperature synthesis (SHS) combining a rapid cooling technique. This method is convenient, low in cost, and capable of being scaled up for processing the bulk nanostructured materials. The solidification microstructure is composed of a relatively coarse, uniformly distributed dendriteto a nanostructured eutectic matrix with α-Fe(B) and t-Fe2B phases. The fine eutectic structure is disorganized, and the precipitation Fe2B is found in the α-Fe(B) phase of the eutectic. The dendrite phase has the t-Fe2B structure rather than α-Fe(B) in the Fe94.3B5.7 alloy, because the growth velocity of t-Fe2B is faster than that of the α-Fe with the deeply super-cooling degree. The coercivity (Hc) and saturation magnetization (Ms) values of the Fe94.3B5.7 alloy are 11 A/m and 1.74T, respectively. Moreover, the Fe94.3B5.7 alloy yields at 1430 MPa and fractures at 1710 MPa with a large ductility of 19.8% at compressive test.

Al–Cu–Fe alloy with a nominal composition of Al62Cu25.5Fe12.5 (at.%) has been fabricated by a combination of pressure-assisted self-propagating high-temperature synthesis and rapid solidification. The as-synthesized Al–Cu–Fe alloy mainly consists of icosahedral quasicrystalline (IQC) ψ-Al65Cu20Fe15 and cubic β-Al (Cu, Fe) solid solution phases, and exhibits finely equiaxed grains with a size ranging from 50 to 200 nm. The mechanism for the formation of the ultrafine-grained IQC phase has been explained.

In this paper, the tribological behaviors of 20 and 40 vol% in situ TiB2 reinforced TiAl-based composites sliding against SiC balls were investigated in artificial sea water, and TiAl alloy was also studied as a comparison. The results showed that the TiAl-TiB2 composites are lubricated in artificial sea water and TiB2 is effective to improve the wear resistance of the TiAl alloy. Also, it was found that the tribological behaviors have a dependency on the applied loads and sliding speeds. Worn surface morphologies and composition together with electrochemical behaviors of the materials were evaluated and related to the tribological behaviors.