Key Engineering Materials Vol. 641

Abstract: Al-coated Mg-Li alloy rods and plates having a homogeneous coating layer of 180μm in thickness have been produced by hot extrusion of Mg-Li alloy billets together with Al disks. The Al-coated Mg-Li alloy exhibits an excellent corrosion resistance in a weight-loss test with a 0.5 mass% HCl aqueous solution, and it has been revealed by a potentiometric corrosion test with a 3 mass% NaCl aqueous solution that the Al-coated Mg-Li alloy has the same electric potential as that of pure Al. Al-coated Mg-Li alloy sheets produced by hot forging of the extruded plates exhibits good elongation of 22 %, 40 % and 130 % at room temperature, 200 °C and 300 °C, respectively.

Abstract: Various allotropic forms of carbon like carbon nanotubes (CNT’s) can have high mechanical, thermal and electrical properties. Because of this phenomena research results are being conducted worldwide on their possible use in electro-technical and electrical industry, for heat removal applications and in the fields of widely understood mechanical industry. Development method of high quality CNT’s is complex and can be long lasting. Because of those difficulties the production cost is very high and price of obtained CNT’s can reach thousands of euros. High cost of pure CNT’s and graphene is a direct reason for numbers of studies, also conducted in this article, on the synthesis of copper and other forms of carbon like i.e. activated carbon. Authors of this article state that also with the use of activated carbon one can achieve increase of copper mechanical, electrical, and technological properties. In this paper research results on copper and activated carbon (CWZ14) synthesis method are presented along with the research results of electrical, mechanical, rheological and micro-structural properties for obtained composites.

Abstract: The results of research into manufacturing of layered brazing materials with silver brazing alloy BAg22 content and copper obtained in pressing at elevated temperature and rolling process for use in cutting tools working in harsh conditions were presented. Mechanical and dimensional properties of the constituent materials of the layered strips with 50 and 75% volume fraction of copper as the inner layer were selected, i.e. the BAg22 alloy strip and the copper strip, for the preliminary join operation in pressing process. Cladding process conditions of the set BAg22/Cu/BAg22 of the original thickness of 32mm for the ratio of layer thicknesses as 1:2:1 and 24mm of the original thickness for the ratio of layer thicknesses as 1:6:1 including the method of semi products surface preparation and range of forces and temperature parameters were specified. Plastic working conditions of pressed composite ingot in hot and cold rolling to the final thickness with the intermediate and final heat treatment parameters were developed.

Abstract: The purpose of the studies was to determine production parameters of AgW50 composite contact material. Fabrication of contact tips from this material was carried out by powder metallurgy method including preparation of the powder mixture, pressing, sintering and optional repressing under pressure of not less than 600 MPa. This technology enables production of contact tips with different shape and size without application of machining. The required material structure, i.e. uniform distribution of tungsten particles in the silver matrix, was achieved by milling conducted in the planetary ball mill. The further operations of this technological process, i.e. optimization of consolidation parameters, enabled fabrication of material characterized by high density and functional (electrical) properties.

Abstract: The paper presents the aspects of trimets manufacturing related to raising quality and economic demands. The comparison of two types of alloys used as a filler metal has been performed. Modification of the chemical composition of brazing alloy, currently used for trimet composite strips in terms of lower silver contents has been proposed. The joining of conventional cemented carbides with steel has been investigated.

Abstract: The effect of plasma gases (argon, helium) on the structure and properties of the WC-CrC-Ni coatings deposited at the graphite substrate has been investigated. The coatings were deposited by plasma spraying method in equipment Cham Pro –Thermal Spray Systems produced by Sulzer company. The microstructure of coatings were investigated by light microscopy (MO) and scanning electron microscopy (SEM). The performed investigations have been shown that with the increasing of amounts of argon and reducing volumes of helium and nitrogen, the microhardnees increased. The plasma gases also influenced on the porosity of coatings. Keywords: WC-CrC-Ni coatings, plasma spraying, microstructure, porosity Acknowledgement: The work was supported by project No INNOTECH – K2/IN2/9/181851/NCBR/13

Abstract: The Diamond like carbon (DLC) and diamond coatings were deposited on a steel substrate using plasma assisted chemical vapor deposition (PA CVD) method. The parameters of deposition were analyzed in relation to the effectiveness of the process and the quality of coatings. It was found that the DLC coatings formed only at specific conditions of temperature and pressure of precursor gases. The characterization of coatings were performed by Raman spectromicroscopy, X-ray diffraction and infrared spectromicroscopy which allowed us to recognize the dominant phases and the distribution of bonds inside the coatings. The chemical bonds such as sp² C-C, sp³ CH₃/CH₂ and sp³ CH were found in microstructure coatings. The maps of distribution of bonds in the coatings were also prepared. Additionally, their microstructure was investigated by scanning electron microscopes which have revealed a spherical grains morphology of the coatings.

Abstract: This work discusses the influence of the processing temperature, time and processing strain on the microstructure of the Ti6Al2Sn4Zr6Mo alloy. The Ti6Al2Sn4Zr6Mo alloy belongs to the two-phase (α+β) type of titanium alloys. The samples were compressed with the use of the Gleeble thermo-mechanical simulator at the temperatures of: 800, 900, 950, 1000 and 1100°C and at the strain rates of: 0.01; 0.1; 1; 10 and 100 s^-1 to a total true strain of 1. The occurrence of the primary α phase in the Ti6Al2Sn4Zr6Mo alloy was investigated. The diagram showing the influence of the processing temperature and the strain rate on the dynamic recrystallization of the β phase was presented.The occurrence of the primary α phase precipitates blocks the grain growth. Therefore, the plastic deformation of this alloy should be carried out at a temperature at which the separation of the primary α phase occurs to finally obtain a material with a fine grain.

Abstract: The results of investigations of the influence of the ageing temperature on the selected mechanical properties i.e. hardness, fracture toughness (examined by the linear elastic fracture mechanics - K_Ic test) and impact strength (KV) of two-phase Ti6Al7Nb alloy, are presented in the hereby paper. Investigations were performed in the ageing temperatures range: 450÷650°C of the alloy previously undercooled from the selected heating temperature (in two-phase range) - equal 970°C. The heating temperature was determined on the basis of the dilatometric curve of the alloy heating in the system ΔL = f ((T), where: ΔL – change of the sample length, T – temperature, which was then differentiated in the system: ΔL/ΔT = f (T). The dilatometer L78 R.I.T.A of the LINSEIS Company was used in the tests. Investigations of the alloy microstructure in the ageing temperatures range 450÷650°C were carried out by means of the light microscope Axiovert 200 MAT of the Carl Zeiss Company. It was found that nearly equiaxial grains of the primary α phase occur in the microstructure (of the volume fraction app. 30%) and that the volume fraction of the new lamellar α phase - formed from the supersaturated β phase - increases. With an increase of the alloy ageing temperature, in the mentioned above range, a small increase of its hardness from 305 to 324HV as well as a decrease of stress intensity factor K_Ic from 67.3 to 48.6 MPa x m^1/2 and impact strength (KV) from 40.2 to 31.3 J. The impact tests results were supplemented by the fractographic documentation. It was found, that the characteristic features of the fractures of impact test samples do not exhibit essential differences in dependence of the ageing temperature and material hardness. The fractographic investigations were performed by means of the scanning electron microscope NovaNanoSEM 450.

Abstract: The published results of the research on crystallization process of nickel base superalloy castings rarely take into account the effect of the wall thickness of the casting. Current study presents a comprehensive assessment of the impact of molten alloy temperature, mould temperature, mould thermal insulation and casting diameter on crystallization process of polycrystalline nickel base superalloy. Research was designed and conducted as an factorial experiment at two levels. Different diameter samples were designed and optimised by the numerical simulation of solidification process using ProCAST software. Inconel 713C nickel based superalloy was cast into alumina-silicate moulds produced by lost wax technique. Casting temperature during solidification was measured using thermocouples installed in sections having a diameter of 10 and 20 mm. Statistical analysis of the influence of the main process parameters and casting diameter on cooling rate, total freezing temperature range and critical temperature range was performed. Cooling rates in the range from 0.21 to 1.24°C/s were obtained. It was found that diameter of the casting, mould temperature and the thermal insulation of the mould had significant effect on the cooling rate.