Licai Fu

The Tribological Behavior of a Ti-46Al-2Cr-2Nb Alloy Under Liquid Paraffine Lubrication

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.

Nanostructured Hypoeutectic Fe-B Alloy Prepared by a Self-propagating High Temperature Synthesis Combining a Rapid Cooling Technique.

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.

Combustion Synthesis and Characterization of Bulk Nanocrystalline

Bulk nanocrystalline Fe88Si12 alloy is fabricated by a combustion synthesis processing that is convenient, low in cost, and capable of being scaled up. The Fe88Si12 alloy consists of two phases: ¿-Fe(Si) and Fe3Si. It is a composite structure of meshwork dispersed in a matrix. The meshwork is a few micrometers in length and 0.5-1 ¿m in diameter, and the grain size of the matrix is in the range of 5-15 nm. The nanocrystalline Fe88Si12 alloy is yielded at 1760 MPa with a large ductility of 14.6% in compressive test. Moreover, the coercive force of the product is approximately 3.6 A/m and saturation magnetization is about 196 emu/g. The results suggest that the product exhibits good mechanical behavior and soft magnet properties.

{\bf Fe}_{\bf 88} {\bf Si}_{\bf 12}

The limited room temperature ductility of nanostructured materials with uniform grain size distribution restricts practical applications. To circumvent this problem, we employ a self-propagating high temperature synthesis combining a rapid solidification process to prepare the bulk nano-eutectic Fe83B17 alloy, which can lead to simultaneous high strength and large ductility. The microstructure of the Fe83B17 alloy has been examined in detail using x-ray diffraction, scanning electron microscopy and transmission electron microscopy. The Fe83B17 alloy is composed of the eutectic of tetragonal Fe2B and α-Fe phases. The t-Fe2B and α-Fe phases display a fine lamellar eutectic structure with lamellar spacing of about 50 nm. The size of the eutectic colonies is in the range 3–25 µm. High yield strength (1089 MPa) and large ductility (~24.9%) are observed simultaneously in mechanical behaviour tests. The rotation of the eutectic colonies, accompanying viscosity plastic flows to release the localization of the shear stress, can contribute to the simultaneous high strength and large ductility.

Alloy

In this paper, we investigated the effect of counterface of AISI 52100 steel and ceramics of SiC, Al2O3, and Si3N4 on the tribological behavior of Ti3AlC2 at ambient. The results showed that the tribological properties of Ti3AlC2 are strongly dependent on the counterfaces. Under present test conditions, the tribocouple of Ti3AlC2/SiC exhibits lower coefficient of friction (CoF) 0.40, Ti3AlC2/AISI 52100 steel shows a rising CoF from 0.1 to 0.63, both Ti3AlC2/Si3N4 and Ti3AlC2/Al2O3 tribopartners exhibit higher CoF of 1.22 in average. The Ti3AlC2 exhibits the lowest wear rate sliding against AISI 52100 steel, the wear rate of Ti3AlC2 sliding against Al2O3, Si3N4, and SiC are higher and comparable. The morphologies of the worn surfaces of the Ti3AlC2 are observed by scanning electron microscopy, and the element states are analyzed by X-ray photoelectron spectroscopy. The wear mechanisms are discussed.

Microstructure and mechanical behaviour of nano-eutectic Fe83B17 alloy prepared by a self-propagating high temperature synthesis combining rapid solidification

In this study, bulk nanostructured composite Cu60Fe40 alloy is prepared by a combustion synthesis technique. The prepared Cu60Fe40 alloy consists of Cu(Fe) solid solution and Fe(Cu) solid solution phases. The large-scaled compositional segregation in the Cu-rich and Fe-rich phases is not observed, respectively. A few micron-sized dendrite (Fe(Cu) solid solution) is embedded into the nanostructured matrix (Cu(Fe) solid solution). The grain size of the matrix is in the range 50–300 nm. The yield and fracture strength of the Cu60Fe40 alloy are 540 and 1050 MPa, respectively, and the fracture strain obtained from the compression test is about 20.9%. The Cu60Fe40 alloy displays notable work hardening in the compressive deformation.

Effect of Counterface on the Tribological Behavior of Ti3AlC2 at Ambient

A large bulk nanostructured Ni65Al21Cr14 alloy with dimensions of Φ 100mm × 6mm was produced by combustion synthesis technique followed with rapid solidification. The Ni65Al21Cr14 alloy was composed of γ′-Ni3Al/γ-Ni(Al, Cr) eutectic matrix and γ-Ni(Al, Cr) dendrite. The eutectic matrix consisted of 80-150nm cuboidal γ′-Ni3Al and 2-5 nm γ-Ni(Al, Cr) boundary. The dentrite was comprised of high-density growth twins with about 3-20 nm in width. The nanostructured Ni65Al21Cr14 alloy exhibited simultaneously high fracture strength of 2200MPa and good ductility of 26% in compression test.

Microstructure and mechanical behavior of nanostructured composite Cu60Fe40 alloy

Abstract The tribological behavior of Fe3Al composite with 60 wt.% Fe3AlC0.5 under air and vacuum was studied. The composite exhibited a lower wear rate but somewhat higher friction coefficient under air than vacuum. The wear rates increased and the friction coefficients decreased with increasing the applied load under both conditions. The sub-layer of the worn surface under vacuum suffered from severe plastic deformation. This was not the case under air due to protection by surface oxide films. The dominant wear mechanisms were plastic deformation and adhesion under vacuum and oxidative wear and slight delamination under air.

Combustion synthesis of large bulk nanostructured Ni 65 Al 21 Cr 14 alloy

Fe70Ni30 alloy with nanoscale twins was obtained by deep cryogenic treatment (DCT) of coarse grained Fe70Ni30 alloy (CG-Fe70Ni30) at liquid nitrogen temperature. The tribological behavior of DCT-Fe70Ni30 alloy was investigated under liquid paraffin oil lubrication compared with that of CG-Fe70Ni30 alloy. The experimental results showed that the wear resistance of DCT-Fe70Ni30 alloy was improved significantly after the introduction of nanoscale twins, and DCT-Fe70Ni30 alloy also showed a little lower friction coefficient relative to CG-Fe70Ni30 alloy. The results indicated that twins play a positive role in the materials friction-reduction and anti-wear properties, which is attributed to the better oil-adsorption ability and enhanced hardness of DCT-Fe70Ni30 alloy caused by structural refinement. Wear mechanisms were discussed.

Tribological behavior of Fe3Al-60 wt.% Fe3AlC0.5 composite under air and vacuum conditions

The wear behavior of Ag implantation GH4169 alloy by ion beam assisted bombardment was measured under lower applied load and sliding speed. The wear rate of GH4169 alloy decreased from 2.58 × 10−4 mm3·m−1 to 6.25 ×10−5 mm3·m−1 after Ag implantation. The friction coefficient had not mostly been changed. After Ag implantation, Ag and Ag2O were detected on the worn surface of GH4169 alloy, which benefits the formation of continuous lubrication and protected layers. The predominant wear mechanism changed from abrasion and adhesion wear to oxidation and adhesion wear. In addition, the hardness increased. So, the wear resistance of GH4169 alloy under lower applied load and sliding speed can be improved with Ag implantation by ion beam assisted bombardment.