Papers by Keyword: NiAl

Abstract: The sintering at (1.35x103) °C for 90 minutes under argon gas atmosphere formed a nickel aluminide NiAl-based composite strengthened with yttrium oxide Y₂O₃ with the addition of cobalt in the current sample. (ASTM E140 – 12b) was used to perform the Brinell hardness test. The addition of cobalt increases the hardness of the (NiAl-Y₂O₃) composite. The hardness of NiAl-30Y₂O₃ composite improved from 341HB to 359HB after 1.5 wt.% Co was added, although the hardness improved to (381-383)HB after 2-2.5 percent Co was added. According to the findings of the wear examination, the inclusion of cobalt decreases the wear intensity of NiAl-30Y₂O₃, according to the findings of the wear examination. The adhesion wear rate reduces from 7.61 * 10^-6 gr / cm to 6.72 * 10^-6 gr / cm when 1.5 wt. percent Co is added, thus inserting 2-2.5 wt. percent Co reduces the rate to 5.87* 10^-6 – 5.22* 10^-6 gr /cm.

Abstract: Aluminium as matrix in particulars have been vastlys investigateds, this is becauses of the diverses applicationss of aluminium dues to its exceptional propertiess. Material scientistss alwayss face a challenges when it comess to the tribologicals and mechanicals propertiess of aluminium, as it exudess rather poors behaviours in these aspectss. Hences this works aims to improves the mechanicals and corrosives resistances of Aluminiums by reinforcings with aluminum oxides and Nickel throughs stir casting usings vortex techniques. Al-Ni-Al₂O₃ composites with percentages of Ni fixed at 20 % and Al₂O₃ differed through 4-8% in incrementss of 2 wt. % . Composites material was prepareds by stir castings using vortex techniques. The hardness value of the aluminiums matrix composites improved with increaseds percentages of Al₂O₃, maximums increase was obtaineds for 8% Al₂O₃ composite, viewing an increases of about 55%. A generals corrosions and erosion-corrosions for the Al-20%Ni bases alloys and the prepareds composites were carrieds out in 3.5wt% NaCl solutions as corrosives mediums for general corrosions while in erosion-corrosions with impacts angles 90° in slurry solutions ( 1wt%SiO₂ sand in 3.5wt% NaCl solution as the erodent). It was founds that the general corrosions rates for composite specimens is lower than thats of the bases alloy (Al-20%Ni). In case of erosion-corrosion resultss, it was founds that the erosion corrosions resistances property of the prepareds composites improveds significantlys with the increaseds percentages of Al₂O₃. There wass a noticeable improvements in the corrosion resistances of the aluminiums composites compareds to its purest forms, owing to the presences of nickel. Howevers, the increases in Al₂O₃ percentages decrease the corrosions rates. The extreme decreases was obtaineds for 8% Al₂O₃ composites, with a decreases of 26% corrosion rates in (mpy) unit for composites material is lowers than that of the bases alloys.

Abstract: Nickel aluminides have shown great potential as high temperature structural materials. In this study, two classes of nickel aluminide were reinforced with 0.5wt% MWCNTs. Starting powders of nickel, aluminium and MWCNTs were ball milled together using a two stage milling regime and consolidated by spark plasma sintering. The effect of MWCNT reinforcement on the hardness of two classes of nickel aluminide was investigated. Microhardness values revealed a lack of dependence on densification for the NiAl₃ composites. The microhardness values of NiAl-CNT reduced with MWCNT addition whereas microhardness values of NiAl₃-CNT increased with MWCNT addition.

Abstract: In this study the effect of thermal spray process on wear resistance of NiAl/Cr2C3 thermal spray coating has been investigated. For this purpose the NiAl power mixed with 10 %wt. Cr2C3 powder and milled for 1 hrs at argon atmosphere. The APS parameters such as voltage (V), current (A), spray distance (mm), powder feed rate (gr/min), were optimize using a response surface methodology. For investigation effect of spray parameters on quality of coatings, the porosity and wear resistance of coatings analyzed with SEM and pin on disk wear test. Results show that increase of voltage and current are more effective other parameters. Increasing of powder feed rate and spray distance raised porosity of coatings intensively.

Abstract: In this study, αAlB₁₂-20vol% NiAl cermet disk specimens were prepared by spark plasma sintering, and their microstructure, Knoop hardness, fracture toughness, and friction and wear properties were investigated. The αAlB₁₂-20vol% NiAl disk specimens were obtained by spark plasma sintering blended αAlB₁₂ and NiAl powder at 1573 K for 600 seconds. No reaction product phases were observed between the αAlB₁₂ and NiAl phases. The αAlB₁₂-20vol% NiAl disk specimens exhibited friction coefficients lower than 0.2 and specific wear rates as low as 1.3 × 10^-6 mm³/Nm when sliding against Si₃N₄ ball specimens in water. O-rich phases were observed on the worn surfaces of the NiAl and αAlB₁₂-20vol% NiAl disk specimens after sliding against Si₃N₄ ball specimens in water. The Knoop hardness of the disk specimens was as high as 10 GPa and the fracture toughness was as high as 7 MPa m^1/2.

Abstract: This paper presents the results of a study of the oxidation behavior of NiAl produced by gel combustion synthesis calcined at two different temperatures. The objective is to compare the oxide growth rates, oxide scale composition, morphology and elemental composition of the sample powder subjected to isothermal oxidation and calcined at 1050 °C and 1300 °C for 1, 2, 4 and 10 hours by means of mass gain measurements, X-ray diffraction (XRD), field emission scanning electron microsocopy (FESEM) and energy-dispersive spectrometry (EDX) in order to investigate the reliability of the gel combustion synthesis method and evaluate the effect of calcination temperature on the oxidation behaviour of the powder. It was found that for the sample calcined at 1300°C the sample was made up mainly of metastable and stable alumina before oxidation and stable alpha alumina after oxidation whereas for the powder calcined at 1050°C the sample was mainly composed of detrimental mixed oxides before and after oxidation. Overall findings indicate that the oxidation behavior of the powder calcined at 1300°C is more protective compared to the powder calcined at 1050°C.

Abstract: NiAl is widely used for elevated temperature application because it gives better properties, especially in the gas turbine application. This study was done in order to investigate the effects of calcination temperature on NiAl and α-Al₂O₃ formation using gel combustion synthesis method. This method used fatty alcohol and fatty acid ester for producing NiAl powders. X-Ray diffraction patterns of calcined samples exhibited NiAl and α-Al₂O₃ at temperature 1050°C. Therefore, nanostructured NiAl-α- Al₂O₃ can be successfully produced with the gel combustion method using less expensive and more environmental friendly fatty alcohol and fatty acid ester as fuels.

Abstract: SHS process in the multilayer nanofoils possesses many unique properties, such as unexpectedly high propagating rate (up to 10² m/s) and extremely short time of reaction and product phase formation (10^-7 – 10^-6 s). Understanding of the mechanism of this process has critical significance not only for the theory of SHS, but also for various applications of the reactive nanofilms, e.g., joining of dissimilar materials and items. An overview of new experimental results shows existence of complex structure of the reaction waves in the multilayer foils and reveals some new “solid-flame” combustion phenomena at macroscopic level. Comparison of these data with the study of the micro- and nano-scale processes by different experimental methods sheds new light on the intrinsic mechanism of the process. The roles of the melts, reactive exothermic dissolution and methastable phases are discussed.

Abstract: 800x600 Intermetallics are compounds of two metals or of metal(s) and semimetal(s). Their structures are usually different from those of the constituents. Some intermetallics are interesting functional materials, others have attracted attention as high-temperature structural materials. We remind the reader of some fundamentals of solid-state diffusion and to the major techniques for tracer diffusion measurements, interdiffusion studies and the growth kinetics of layers in solid diffusion couples. Starting from self-diffusion, which is the most basic diffusion phenomenon in any solid, the paper covers the main features of diffusion in binary intermetallics from the systems Cu-Zn, Ni-Al, Fe-Al, Mg-Al, Ni-Ge, Ni-Ga, Fe-Si, Ti-Al, Ni-Mn, Mo-Si, Co-Nb and Ni-Nb.. We illustrate the influence of phase transitions on diffusion and point out some common features of diffusion in intermetallics. We discuss in detail diffusion in silicides of iron, molybdenum and of silicides of refractory metals. We also consider aluminides of iron, nickel, and titanium and in the aluminium-magnesium system. We consider diffusion in intermetallics of the cobalt-niobium and nickel-niobium system and in in the Nb-Sn and V-Ga systems. We finish with some remarks about grain boundary diffusion in intermetallics. Normal 0 21 false false false UK X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif";}

Abstract: The technique of synthesis of Ni+16mass%Al open cell type porous intermetallic materials that can be treated in inert or regenerative atmospheres at temperature up to 1600 K without changing their functional properties has been developed. Materials with Ni₃Al + NiAl phase composition, porosity of 42 %, sizes of transport pores up to 10 μm, sizes of core elements equal to 40 μm, and specific surface of open porosity of 90 mm^-1 have been produced. It is demonstrated that after complete oxidation of the given materials, the NiO-NiAl₂O₄ composite is formed, whose reduction in hydrogen flux results in the formation of Ni-NiAl₂O₄ cermet; the shape of the porous material in the course of oxidation/reduction does not change.