| 1. |
- An, T., et al.
(författare)
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Analysis on microstructure and friction wear performance of chromium carbide/Ni 3Al composite surfacing layer
- 2012
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Ingår i: Hanjie Xuebao/Transactions of the China Welding Institution. - 0253-360X. ; 33:2, s. 101-104
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Tidskriftsartikel (refereegranskat)abstract
- Microstructure of chromium carbide reinforced Ni 3Al-based matrix composite coating prepared by argon tungsten-arc welding was investigated with optical microscope, scanning electron microscopy (SEM), electron probe micro-analysis (EPMA) and X-ray diffraction (XRD). The wear performance of the coating and cast iron of piston ring were tested by a Pin-on-Disc tribometer. The results indicated that the Ni 3Al-based matrix was formed during welding, a large number of fine carbide particles such as Cr 3C 2 and Cr 7C 3 dispersed in it; The particle of Cr 3C 2 in welding wire was dissolved and re-precipitated during hardfacing. The re-precipitation of chromium carbide particle contains Fe, Ni elements and forms strong metallurgically bond with Ni 3Al-based matrix. Diffuse distribution of chromium carbide particles and Cr solid-solution in Ni 3Al-based matrix, makes the surfacing layer with higher hardness. The hardfaceing layer shows excellent dry friction wear resistance and its friction coefficient is 0.23, lower than 0.39 which is the friction coefficient of piston material of vermicular graphite cast iron. The wear rate of hardfaceing layer is only 43 percent of vermicular graphite cast iron.
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| 2. |
- Feng, S., et al.
(författare)
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Formation of In-Situ Dispersion Strengthening Particles in Cast FeCrAl Alloy
- 2010
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Ingår i: Journal of Iron and Steel Research International. - 1006-706X. ; 17:2, s. 74-78
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Tidskriftsartikel (refereegranskat)abstract
- In order to fabricate dispersion strengthened alloys strengthened by submicron-sized or nano-sized stable particles through casting routes, understanding of the formation process of dispersion strengthening particles in metal melt is of significance. Thus, nano NiO and TiO2 particles were selected as reactant to form in-situ dispersion strengthening oxide particles in Fe20Cr5Al alloy. Nano NiO and TiO2 particle powder was separately dispersed into nano Ni powder first. The loose mixed nano powder was added in Fe20Cr5Al alloy melt when pouring the melt into mold. The study shows that nano NiO particles were not as effective as nano TiO2 particles in forming dispersion strengthening Al2O3 particles. The final diameters of dispersion strengthening oxide particles arose from nano TiO2 particles were of submicron. The Brownian collision of particles had caused this coarsening.
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| 3. |
- Feng, Yingkai, et al.
(författare)
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Effect of Cr3C2 Content on the Microstructure and Wear Resistance of Fe3Al/Cr3C2 Composites
- 2022
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Ingår i: Coatings. - : MDPI AG. - 2079-6412. ; 12:12
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, an engine piston ring coating comprising composite material of Fe3Al and Cr3C2 mixed powder was prepared by laser cladding onto carbon structural steel. The microstructure and tribological properties of the cladding materials were investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and wear tests. The influence mechanism of the Cr3C2 content in cladding powder was studied. During the process of wear, the soft Fe3Al/Fe2AlCr matrix is first ground off, and the hard Cr7C3 phase initially supports the abrasive surface before being worn away into hard particles, resulting in abrasive wear. With the increase in Cr3C2 content, the hardness of the cladding layer increases, the proportion of the Cr7C3 phase increases, and the morphology changes from a sparse network to a dense floccule. Of the cladding layers with different Cr3C2 content, the 15 wt.% Cr3C2 cladding layer had the lowest friction coefficient, and the 25 wt.% Cr3C2 cladding layer had the lowest wear rate. The low wear rate of the 25 wt.% Cr3C2 cladding layer can be attributed to the fact that adhesive wear does not easily occur and the fine microstructure of the strengthening phase, which facilitates better separation in the grinding surfaces.
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| 4. |
- Fu, L., et al.
(författare)
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Effects of Cr3C2 content and temperature on sliding friction and wear behaviors of Cr3C2/Ni3Al composite materials
- 2018
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 414-415, s. 163-173
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Tidskriftsartikel (refereegranskat)abstract
- Chromium carbide (Cr3C2)-reinforced Ni3Al matrix composites, which possess excellent high-temperature strength and wear resistance, are considered as potential high-temperature wear-resistant materials. In this study, effects of Cr3C2content on the friction and wear properties of Cr3C2/Ni3Al composites and their counterpart gray cast iron disks were investigated at different temperatures. The worn surface morphologies of the Cr3C2/Ni3Al composites and gray cast iron disks were analyzed to understand their wear mechanisms. The analysis results showed that in the Ni3Al matrix composites, a combination of abrasive wear and adhesive wear occurred at room temperature, whereas adhesive wear was severer at 200 °C. Furthermore, the optimum Cr3C2contents of the Cr3C2/Ni3Al composites were found to be 18 vol% and 12 vol% at room temperature and 200 °C, respectively. The volume loss of the composites increased with an increase in the fraction of the Cr3C2strengthening phase at 350 °C. The wear resistance of the gray cast iron disks decreased with an increase in temperature. In contrast, the wear resistance of the Ni3Al matrix composites increased with an increase in temperature. This increased wear resistance of the composites is attributed to the transformation of their wear mechanism with increasing temperature.
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| 5. |
- Fu, L., et al.
(författare)
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Microstructure and tribological properties of Cr3C2/Ni3Al composite materials prepared by hot isostatic pressing (HIP)
- 2017
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Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 115:115, s. 203-212
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Tidskriftsartikel (refereegranskat)abstract
- Ni3Al-based composites with different Cr3C2 contents were fabricated by the hot isostatic pressing (HIP) technique.The microstructure, phase constitution, and tribological properties of the composites were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and pin-on-disk wear tests. The results revealed that the strengthening phase is distributed homogeneously in the Ni3Al matrix. During the HIP process, M7C3 (M = Cr, Fe) is formed by diffusion of Fe, C, and Cr to the interface between the Cr3C2 particles and Ni3Al matrix. The diffusion process binds the phases and is important for improving the wear resistance of Cr3C2/Ni3Al composites. The wear measurements demonstrated that micro-cutting and fatigue wear are the dominant mechanisms for this tribological pair. The wear resistance of Cr3C2/Ni3Al composites is significantly improved by the addition of Cr3C2 particles.When the content of Cr3C2 is within a certain range, the wear resistance of Cr3C2/Ni3Al composites increases as the Cr3C2 content increases. However, the addition of excess Cr3C2 (for example, 24 vol% in this work) could lead to a decrease in the wear resistance of the composites. In addition, the average friction coefficients and wear of the counterpart decrease with increasing Cr3C2 addition.
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| 6. |
- Gong, Karin Anne Xia, 1965
(författare)
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A Ni3Al-alloy and its Composites as Potential Wear Resistant Materials for Advanced Applications
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Ni3Al-based intermetallic alloys as engineering materials in service, they may be subjected to a wear environment of some sort. Hence, it is technologically important to understand the tribological response and to determine methodologies to improve wear resistance of these advanced materials. The tribological performance of Ni3Al-based alloys is among the mostly promising in the group of intermetallics. Therefore, a Fe-alloyed Ni3Al (NAC-alloy) with composition of Ni-18.8Al-10.7Fe-0.5Mn-0.5Ti-0.2B (at.%) and its composites tailored respectively with hard Cr3C2 and soft MnS particles were selected in this thesis work for investigation. The testing materials were prepared by powder metallurgy, vacuum casting process and cladding technique, respectively. To evaluate the friction coefficient and specific wear rate of the test materials, a conventional pin-on-disk (POD) tribometer was used. The monolithic NAC-alloy showed similar wear properties with respect to its specific wear rate and friction coefficient under the applied pin-on-disk testing conditions to those of commercial vermicular graphite cast iron. Unfortunately, NAC-alloy worked inadequately with its counterpart disk of a grey cast iron used as liner material in engines. Added hard Cr3C2 particles reduced wear on both sides of the pin and disk by 50%. The soft MnS particles, which functioned as an effective solid lubricant, reduced friction coefficient of the friction pair and decreased specific wear rate of the grey cast iron disk by 20%. However, the specific wear rate of the pin was not lowered. In general, the NAC-alloy may function well as a matrix material to develop wear-resistant composites. In this thesis study, it was also recognized that development of metallurgical processes may play an important role for further improving wear properties of the investigated materials.For further understanding wear mechanism of the NAC-alloy and its composites, nanoindentation and numerical simulation were applied to study friction-induced nanohardness variation in subsurface layer of the tested materials. An exponential decay fitting function was applied and the deformation strain of the monolithic NAC-alloy versus surface distance was derived. The addition of hard Cr3C2 particles reduced the thickness of the subsurface layer and retained the same peak hardness of the friction surface as the monolithic NAC-alloy. Due to ineffective strain hardening, the addition of soft MnS particles decreased both of the thickness of subsurface layer and the peak-hardness on the friction surface. These results were coupled to the experimental data from pin-on-disk tests and microstructural analysis.
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| 7. |
- Gong, Karin Anne Xia, 1965
(författare)
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Investigation on subsurface layer of Ni3Al-alloy and its composites induced by friction
- 2012
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Ingår i: International Conference on Innovative Technologies, IN-TECH 2012. ; , s. 361-364
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Konferensbidrag (refereegranskat)abstract
- Evaluation of the wear behaviour of a Ni3Al-based (NAC) alloy and its composites by pin-on-disk (POD) testing indicates that the wear mechanism of the materials varied from that of traditional multi-phase cast irons. It was recognised that the wear of a Ni3A-based alloy and its composites was mainly caused by their plastic deformation and resulted in the formation of a specific subsurface layer at the worn surface. Nanoindentation and numerical regression analysis were further applied to study the friction induced on the subsurface layer of the alloy and its composites. Fitting functions and relevant curves of nanohardness of the Ni3Al matrix versus the surface distance from the worn surface, compressive deformation strain of the monolithic Ni3Al-based alloy versus nanohardness, and the friction-induced strain of the monolithic Ni3Al-based alloy versus surface distance were determined. It was determined that gradually distributed plastic strain with various microstructures was induced in the subsurface layer by friction. The addition of hard Cr3C2 particles reduced the thickness of the subsurface layer and retained the same peak hardness of the friction surface as the monolithic Ni3Al-alloy, which indicates a 50% wear rate reduction on both sides of the pin and disk. The use of MnS particles as a solid lubricant was studied in a NAC-alloy/MnS composite. An ineffective strain-hardening effect on the friction surface of the composite led to a less protected surface layer and an unimproved specific wear rate, though a low wear rate on its counterpart disk and a low friction coefficient of the friction pair were obtained. Finally, a kinetic and periodic process was proposed and used to understand the wear mechanism of the studied Ni3Al-based materials.
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| 8. |
- Gong, Karin Anne Xia, 1965, et al.
(författare)
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Ni3Al-based Intermetallic Alloys as A New Type of High-Temperature and Wear-Resistant Materials
- 2007
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Ingår i: Journal of Iron and Steel Research International. - 1006-706X. ; 14:5, Suppl. 1, s. 21-25
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Tidskriftsartikel (refereegranskat)abstract
- Some intermetallics as high-temperature wear-resistant materials attracted attention of material researchers due to their intrinsic long-range ordered crystalline structures with strong oriented atomic bonding. In the group, Ni3Al-based intermetallic alloys are especially interesting for certain tribological applications. In this work, the wear-behaviour of an existed Ni3Al-based alloy, 77.7Ni-9.8Al-11.5Fe-0.5Mn-0.5Ti-0.1B in weight percentage, and its composites reinforced by Cr3C2-particles were studied, and related to their microstructures. HIPing and casting processes were applied for preparing the materials. Wear-rate of the testing materials under different loads and their scuffing resistance were measured by Pin-on-Disk method. The tested materials were analysed by SEM, EDS, and XRD techniques. The results revealed that the single phase Ni3Al-based alloy showed a reasonable wear-resistance, compared to a duplex microstructure. And, the investigation also indicated that the hard Cr-carbide played a positive role on tribological intermetallics, especially for reducing the wear-rate.
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| 9. |
- Gong, Karin Anne Xia, 1965
(författare)
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Study of Ni3Al- and MoSi2-based Materials for High Temperature Structural Applications
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In general, the potential of current conventional high-temperature materials has been exploited to a large extent. The industries are therefore looking forward to development of alternative materials for their industrials application, which would be lighter, stronger and having improved higher temperature potential compared to the presently available alloys. Among the various high temperature materials for the future, intermetallics-base alloys are prime candidates for alternative materials. In this thesis work, Ni3Al- and MoSi2-based materials were specially investigated for their industrial.On Ni3Al-based materials Attractive engineering properties of Ni3Al alloys is their increasing yield strength with increasing temperature up to about 650-750 ºC. This type of strength behaviour suggested that the Ni3Al-based intermetallic alloys may have good wear properties in the peak-strength temperature range. Consequently, investigations of their sliding friction and wear were initiated. In fact, a number of laboratory studies have indicated that Ni3Al-based alloys have significant potential in wear-critical applications, especially in cavitations erosion and in sliding wear at the temperature range between 400 ºC and 650 ºC. In this work, an existed Ni3Al-based alloy 77.7Ni-9.8Al-11.5Fe-0.5Mn-0.5Ti-0.1B in weight percentages and its composite reinforced by 6 vol. % Cr3C2-particles were studied and related to their microstructures. Hot isostatic pressing and casting were applied for preparing the materials. Wear rate of the test materials under different loads and their scuffing resistance were measured by Pin-on-Disk method. SEM, EDS, XRD, and EBSD techniques were used to observe the microstructures and identify the phase constitutions of the tested materials. The tribological performance related to the analytical results revealed that the single phase Ni3Al-based alloy showed a better wear-resistance compared to duplex microstructure. And the investigation also indicated that the hard Cr-carbide played a positive role on tribological intermetallics reducing the wear-rate.On MoSi2-based materialsMoSi2 is presently considered as one of the most promising due to its high melting point (2030ºC) and excellent elevated-temperature oxidation resistance. However, like most of other intermetallics, the major problem, which has impeded their use, as high temperature materials, is their poor ductility and toughness during brittle-to-ductile transition temperature, BDTT, and low strength level above at temperature. In other words, their low temperature strength is limited by brittle fracture while the high temperature strength is governed by plastic flow. From the earlier investigations it was clear that the addition of alloying elements could not make the monolithic MoSi2 compound having the right combination of ambient temperature toughness and high temperature strengthen. For the most demand depends on the development of engineered composite materials.In this work, the attention was mostly focused on ZrO2-particles reinforced MoSi2-matrix composites. The working results indicated (1) a PLS process could be a practical and economical method for producing MoSi2-ZrO2 composites; (2) ZrO2-particles of less than 1 μm usually generated the better sintered density, RT-hardness and toughness than of the composites compared with the bigger particles; (3) the composites containing 15 – 25 vol.% unstable zironia (USZ) showed a better toughening effect, compared to the composites having less or more particles; and (4) A deteriorated oxidation resistance of MoSi2-ZrO2 composite compared to its monolithic counterpart is due to the formation of the porous oxide layer of ZrSiO4+SiO2 mixture and a retarded Si diffusion by the inner oxidation and reaction between SiO2 and ZrSiO4. Therefore, an alloying addition for further forming a protective oxide layer is necessary on developing this type of composites.Keywords: Intermetallics, Ni3Al, MoSi2, High temperature materials, Wear-resistant materials, Composites, Toughening.
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| 10. |
- Gong, Karin Anne Xia, 1965
(författare)
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Study On Wear Behaviors Of Ni3al/ Cr-Carbides Cladding Layer On High Strength Steel Substrate
- 2014
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Ingår i: Advanced Materials Research. - 1662-8985 .- 1022-6680. ; Vol. 936, s. pp 1273-1282
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Konferensbidrag (refereegranskat)abstract
- A cladding layer of Ni3Al matrix composite reinforced with 18 vol. % Cr-carbides was applied by using tungsten inert gas (TIG) welding process on high strength steel substrate. The filler metal as welding wire prepared by horizontal continuous casting process with a composition of Ni-2.5C-30Cr-9Al-0.02B (in wt. %) is used. A bulk material of NAC-alloy composite with 18 vol. % Cr3C2-particles produced by Hot Isostatic Pressing (HIP) was also investigated as a reference material. The composition of NAC-alloy is Ni-9.87Al-11.63Fe-0.50Mn-0.50Ti-0.2B in weight percentage. The pin-on-disk (POD) tribometer tests were carried out at room temperature in dry sliding condition at a pressure of 2.83 MPa (20N). The results revealed that Ni3Al/ Cr-carbidescladded layer by TIG process improved wear properties significantly with very low values of the frictioncoefficient (0.13 ± 0.02) and the specific wear rate (0.162 x 10-5 mm3/N·m) as compared to the reference HIP processed composite with the friction coefficient (0.68 ± 0.02) and the specific wear rate (0.908 x10-5 mm3/N·m) under the same testing conditions.
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