A number of laboratory studies have indicated that Ni 3 Al-based alloys have significant potential in wear-critical applications, especially in sliding wear in a temperature range between 400 and 650 • C. In this study, the wear behavior of an iron-alloyed Ni 3 Al with composition of Ni-18.8Al-10.7Fe-0.5Mn-0.5Ti-0.2B in atomic percentage and its composites reinforced by 6 vol.% Cr 3 C 2particles were investigated. Hot isostatic pressing (HIP) and casting processes were applied for preparing the materials. The wear rate of the tested materials under different loads and their scuffing resistance were measured by means of the pin-on-disc method. Analytical SEM, EDS, and XRD techniques were used to observe the microstructures and identify the phase constitutions of the materials. The tribological performance related to the analytical results revealed that the single-phase Ni 3 Al-based alloy showed an improved scuffing resistance, compared to a duplex-phase microstructure. Also, the investigation indicated that the added hard Cr-carbide played a positive role for the tribological behavior of the intermetallics, especially in terms of reducing the wear rate.

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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-carbides cladded layer by TIG process improved wear properties significantly with very low values of the friction coefficient (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.

Iron alloyed Ni,Al with composition of Ni-18. 8A1-10. 7Fe0. 5Mn-0. 5Ti-0.2B in atom percent (NAC alloy) showed attractive tribological properties under unlubrication condition at room temperature. The alloy was prepared by hot isostatic pressing (HIP) process. The wear properties were associated with its intrinsic deformation mechanism. Unfortunately, the single phase NAC-alloy worked inadequately with its counterpart disk, and also showed a poor machinability. In the present work, NAC-alloy matrix composite with 6 % (volume percent) MnS particle addition was studied to improve its wear behaviors and performance on machining. Two metallurgical processes of HIP and vacuum casting were applied to produce the testing materials. Pin-on-disk (POD) measurements were carried out at room temperature. A commercial vermicular graphite cast iron was selected as a reference material. The counterpart disk was made of a grey cast iron as liner material in ship engines. The contact pressures of 2. 83 MPa and 5. 66 MPa were normally applied in the tests. The investigation indicated that MnS particle addition in the NAC-alloy composites functions as an effective solid lubricant, and improved wear properties and machinability of the materials. Obviously, as-cast NAC-alloy with in-situ formed MnSphase was working more effectively with the counterpart, comparing to the HIPed NAC-alloy composite with MnS particles. At the high contact pressure of 5.66 MPa, the specific wear rate of the as-cast NAC-alloy composite was high. The phenomenon of the negative effect is mostly due to the brittle second NiAl phase as evidenced in the microstructure analysis. Key words: HIP processing; friction coefficient; specific wear rate; intermetallics ; sliding wear; casting ; machinability T h e advanced engines require increasingly high working temperatures, running speeds and loads. Therefore, there is a great interest to develop and test new materials. One of the candidates is the intermetallic materials. T h e main driving force for such research into intermetallics has in the past been their attraction for high temperature structural applications. It is only in a few of cases that their tribological properties have been studied. And therefore, there is ample scope in this area for fruitful further research, based on the intrinsic characters of the intermetallics. Especially, the tribological performances of Ni,Al based alloys are the mostly attractive and studied in the intermetallic groups.T h e intermetallic materials have long-range ordered crystalline structures with strong oriented atomic bonding, which should be considered as a benefit to a slow wearing rate of the materials. They also show strong strain-hardenability and yield strength; even the strength is increased with raised temperature up until a certain level. In certain cases, these properties lead to excellent tribological propekties under a certain temperature range. In fact, a number of labora- an initial understanding sliding wear behavior of the materials under unlub...