Anna Góral

Structure Characterization of Ni/Al2O3 Composite Coatings Prepared by Electrodeposition

In the present study, the electrodeposition of composites consisted of metal matrix (nickel) and inert particles (hard nano-sized Al2O3 oxide) has been carried out in a Watt’s type bath of pH 4, at room temperature in a system with the steel rotating disk electrode. The influence of dispersed Al2O3 powder on structure characteristics (morphology, phase composition, texture, residual stresses) of Ni/Al2O3 coatings has been investigated. The crystallographic texture of Ni and Ni/Al2O3 coatings deposited on the steel substrates was analyzed by XRD technique based on the back-reflection pole figures. The “sin2ψ” X-ray diffraction method was used to determine the residual stress as a function of X-ray penetration depth. The influence of Al2O3 particles on the value of the Ni coating microhardness was also analyzed.

Effect of Surface Roughness and Structure Features on Tribological Properties of Electrodeposited Nanocrystalline Ni and Ni/Al2O3 Coatings

Metal matrix composite coatings obtained by electrodeposition are one of the ways of improving the surfaces of materials to enhance their durability and properties required in different applications. This paper presents an analysis of the surface topography, microstructure and properties (residual stresses, microhardness, wear resistance) of Ni/Al2O3 nanocomposite coatings electrodeposited on steel substrates from modified Watt’s-type baths containing various concentrations of Al2O3 nanoparticles and a saccharin additive. The residual stresses measured in the Ni/Al2O3 coatings decreased with an increasing amount of the co-deposited ceramics. It was established that the addition of Al2O3 powder significantly improved the coatings’ microhardness. The wear mechanism changed from adhesive-abrasive to abrasive with a rising amount of Al2O3 particles and coating microhardness. Nanocomposite coatings also exhibited a lower coefficient of friction than that of a pure Ni-electrodeposited coating. The friction was found to depend on the surface roughness, and the smoother surfaces gave lower friction coefficients.

Structure and Martensitic Transformation in NiMnSn Alloy Ribbons with Partial Sn Substitution by Al

The influence of Al substitution for Sn in Ni44Mn43.5AlxSn12.5-x (x= 0, 1, 2, 3) ferromagnetic shape memory alloy ribbons on phase transformation and microstructure evolution is outlined in this paper. Ribbons produced by melt spinning technique showed fully crystalline structure, however non uniform. Energy dispersive spectroscopy microanalysis (EDS) confirmed the average composition of ribbons in accord with the initial alloys. The higher symmetry parent phase was identified with the aid of X-ray diffraction (XRD) as bcc L21 Heusler type structure. The unit cell parameters were determined applying the XRD profile fitting method. It was observed that with increase of Al content unit cell parameters and in turn unit cell volume decrease. This may be attributed to the fact that Al has a smaller radius compared to Sn, which it was substituted for. Differential scanning calorimetry (DSC) measurements did not allow to detect the martensitic transformation above -150°C.

The Microstructure of Rapidly Solidified Al-Zn-Mg-Cu Alloys with Zr Addition

The effect of rapid solidification on the microstructure of Al-Zn-Mg-Cu alloys with 8 wt.% Zn-2 wt.% Mg-2.3 wt.% Cu and 0.2 or 0.5 wt.% of Zr additions were investigated using X-ray diffraction measurements (XRD), scanning (SEM) and transmission electron microscopy (TEM) combined with energy dispersive X-ray (EDX) microanalysis. Rapidly solidified ribbons with thickness of 70-100 m were performed by melt spinning technique. The mould cast alloys as well as the melt spun ribbons revealed dendritic microstructure of (Al) solid solution and η Mg(Zn,Cu)2 phase in interdendritic areas. The refinement of the microstructure and reduction of the volume fraction of the η phase up to 1.7%, as compared to 4% in the mould cast alloys was observed in the ribbons. Copper dissolution up to about 20 wt % in the η phase causes a decrease of the lattice parameters. The Al3Zr primary precipitates were observed in the mould cast alloy containing 0.5 wt % of Zr while in the ribbons all zirconium dissolved in the aluminium solid solution.

Influence of Surface Pretreatment on the Corrosion Resistance of Cold-Sprayed Nickel Coatings in Acidic Chloride Solution

Corrosion resistance of the cold-sprayed nickel coatings deposited on the Ni surface (substrate) without and with abrasive grit-blasting treatment of the substrate was investigated. The corundum powder with different grain sizes was used. The corrosive environment contained an acidic chloride solution. The mechanism of the corrosion of nickel was suggested and discussed. Corrosion electrochemical parameters were determined by electrochemical methods. The corrosion effect of a nickel coating depends on the grain size used to prepare the substrate. The nickel coating after the medium grit-blasting treatment of the substrate was found to be the most corrosion resistant. However, the smallest resistance on the corrosion effect should be attributed to the nickel coating on the substrate after the coarse grit-blasting treatment.

HVOF SPRAYED NANOSTRUCTURED COMPOSITE COATINGS WITH A REDUCED FRICTION COEFFICIENT

Nanostructured materials provide new possibilities, which enable creating composite structures with much better properties than composites obtained from conventional materials. Such a solution facilitates combining selected features of different nanomaterials in order to obtain a composite with the required durability, thermal, insulation, tribological, etc. properties. In the case of a composite containing a solid lubricant, it is comprised of a nanostructured matrix, providing mechanical durability, and an evenly distributed nanostructured solid lubricant. A study of the tribological properties of composite HVOF sprayed from nanostructured WC-12Co mixed with nanostructured Fe3O4, having the properties of the solid lubricant is presented. The coatings were sprayed by means of a Hybrid Diamond Jet system. A T-01 ball on disc tribological tester was used to determine the coefficient of friction on the basis of friction force obtained in the course of continuous measurement at a set load. The result of investigations was compared with properties of coatings sprayed with standard WC-12Co/ Fe3O4. Słowa kluczowe: smar stały, powłoka kompozytowa, płomieniowe natryskiwanie naddźwiękowe. Streszczenie Materiały nanostrukturalne stwarzają nowe możliwości, które pozwalają na tworzenie struktur kompozytowych o właściwościach znacznie lepszych niż te otrzymywane z materiałów konwencjonalnych. Takie rozwiązanie umożliwia łączenie wybranych właściwości różnych nanomateriałów w celu uzyskania kompozytu, który będzie posiadał wymagane właściwości wytrzymałościowe, tribologiczne, cieplne i inne. W przypadku kompozytów zawierających smar stały składają się one z nanostrukturalnej matrycy zapewniającej wytrzymałość mechaniczną i równomiernie rozłożonego nanostrukturalnego smaru stałego. W artykule przedstawiono badania właściwości tribologicznych płomieniowo natryskanego naddźwiękowo kompozytu będącego mieszaniną nanostrukturalnego proszku WC-12Co i nanostrukturalnego proszku Fe3O4 o właściwościach smaru stałego. Powłoki kompozytowe zostały natryskane z użyciem systemu do płomieniowego natryskiwania naddźwiękowego Hybrid Diamond Jet. Tester tribologiczny T-01 typu kulka-pierścień został użyty do zbadania współczynnika tarcia na podstawie pomiaru siły tarcia otrzymanej w wyniku ciągłego pomiaru przy ustalonym obciążeniu. Wyniki badań zostały porównane z właściwościami powłok płomieniowo natryskanymi naddźwiękowo z konwencjonalnych proszków WC-12Co/Fe3O4.

Microstructure of Ni/Al2O3 Electrodeposited Coatings Studied with XRD and SEM Techniques

Our interests are focused on the Ni/Al2O3 nanocomposite coatings electrochemically deposited in modified Watt’s-type baths into which α-Al2O3 nanopowder is added on steel substrates. The effect of different amounts of α-Al2O3 phase in the electrolyte baths on microstructure of electrodeposited Ni/Al2O3 coatings is investigated. In order to study the coatings the non-destructive X-ray diffraction techniques are applied. As indirect techniques, they are supported by imaging methods, especially scanning electron microscopy.

Effect of Fe and V additions on amorphous structure formation in melt spun AlNiZr alloys

Abstract An aluminum-based AlNiZr ternary alloy containing 11 at.% Ni and 5 at.% Zr was modified by substitution of 5% of nickel by either iron or vanadium. Melt spun ribbons were cast under a protective helium atmosphere from 99.9% pure elements at 35 m s−1 linear rate of the copper wheel of the melt spinner. X-ray diffraction studies confirmed that most of the volume of all cast ribbons is amorphous showing a broad amorphous halo, however all alloys have shown a small amount of crystalline α(Al) solid solution. The same phase was identified in quaternary alloys. The ribbons showed high microhardness near 500 HV. Transmission electron microscopy studies enabled identification of a large number of spherical crystals of α(Al) solid solution of size near 200 nm in AlNiZr ribbons, containing less solute elements than the amorphous phase. In alloys with iron and vanadium additions crystallites were larger in the form of discontinuous lamellar precipitates. Differential scanning calorimetric studies enabled identification of a multistage crystallization mechanism and the additions of iron and vanadium caused an increase in crystallization temperatures as compared to ternary AlNiZr alloy