Abstract: The thermo-chemical treatment routes for Renè77 superalloy were developed comprising low activity and high activity aluminizing by CVD method. The influence of the treatment on the oxidation resistance in air and creep resistance of the alloy was examined. The cyclic oxidation tests at 1100°C for 500 cycles were carried out. Creep tests were performed at 982°C at the stress level of 124 and 151.7MPa. The chemical and phase composition of the surface layer was analyzed after aluminizing. It was found that aluminide coating enhanced oxidation resistance of the Renè77 superalloy without deterioration of its mechanical properties.
Abstract: In the paper the aluminide layer was deposited by CVD method on the CMSX 4 single crystal nickel base alloy. The aluminizing process was carried out at the 1050 °C during 8 h. The chemical vapor deposition process was performed by means of AlCl3 aluminum chloride. The effects of aluminizing were verified in microscopic examination (microstructure and depth layer) and chemical composition on the surface and cross-section of aluminide layer. The oxidation resistance in the air atmosphere at the 1100 °C during 1000 h was a criterion of efficiency of CVD process. The hardness distribution on the cross-section aluminide layer before and after oxidation test was investigated. The parabolic mass change was observed during oxidation. Under oxidation test during 120 h on the grain size of NiAl phase was observed the phase transformation β NiAl →Ni3Al. The increase of oxidation time causes decreasing of substrate hardness and stabilization of Topologically Closed Packed phases.
Abstract: Light weight nano/submicrocrystalline materials are promising group of constructional materials combining low density with high mechanical properties. However, their potential application requires extensive testing of functional properties, e.g. tribological ones, which may be significant and determine their practical use. Available information on abrasive wear and friction coefficients in nano/submicrocrystalline materials is rather poor. Therefore the aim of this paper is to fill the gap in the literature in this field. The AlSi12Fe5Cu3Mg alloy (RS422) produced by rapid solidification and plastic consolidation with grain size of basic phase components in the range from 50 nm to 300 nm was examined. Microstructure and mechanical properties of the materials were determined. Abrasive wear tests, static and kinematics friction coefficients measurement were carried out under the surface condition including dry, wet and oil lubricant. The results have been compared to the values of similar quantities determined in the same conditions for conventionally produced alloy AlSi11FeCuMn (AK11). Substantial increase of friction coefficients for RS442 comparing to AlSi11FeCuMn material was found, however, abrasive wear for nano/submicron grained materials were low in comparison to conventional one. Considerable increase of abrasive wear at water presence and very weak attrition at oil lubrication was observed. Relationship between structure and mechanical properties of tested materials was analyzed.
Abstract: Cold forging tools most often fail as a result of wearing down surface layer which works with forming part. Deposition of a hard coating on the working surface is widely applied to increase tool durability. In this respect technologies of production of top layers with the use of nanocomposite materials provide great opportunities of modification of tribological properties. This paper presents results of metallographic, SEM and HRTEM analysis of PVD nanocomposite coatings  (nACVIc, TiCN-CBC and TiCN-NP-MOVIC). The tribological tests with ball on disc (T10) tester and industrial tests of forging tool durability were made. The multilayer nACVIc coating is composed of thin layers with the thickness of approximately 2nm as structured alternately by Al and Ti,N,Si atoms, that is different from TiCN-CBC coating with column structure. A modification of the structure results in change of tribological behavior. The nACVIc nanocomposite coating is characterized by significantly less value of the friction coefficient (0.2) as compared to TiCN-CBC coating (0.7) under the same test conditions.
Abstract: In the present work, the microstructure, phase composition and microhardness of Cr3C2-NiCr, WCCo, and powdered composite NiCrSiBCr10%,Fe2.5%,Si3.1%,Bi2.1%C; NiCrSiBFe5; NiCrSiBCr5; NiCrSiBFe2.5Cr2.5; HVOF coatings applied on the Al-Si substrate have been compared. The coating cross-sections were examined by optical microscopy (OM), scanning electron microscopy (SEM) and electron transmission microscopy (TEM). For hard Cr3C2-NiCr and WC-Co coatings, a total microhardness level of about 860 and 1240 HV, respectively, was obtained. The microhardness of composite coatings was essentially lower and comprised in the range of values between 420 and 540 HV. The lowest level of microhardness showed the NiCrSiBFe2.5Cr2.5 coating. The most refined microstructure was found in Cr3C2 and WC coatings. The mean size of splat granules obtained in Cr3C2-NiCr had the value of about 2.7 m and of 0.5 m in WC-Co. For comparison, the granules obtained in composite coatings had the dimensions of about 30 μm. An Xray diffraction (XRD) revealed the presence of Cr3C2 and WC carbides in Cr3C2-CrNi and WC-Co coatings. In composite coatings, the phases of Cr3Ni5Si2, Ni3Si, FeSi, Fe2B, Cr3Si, BCr as well as other phases were found. The existence of the analyzed phases was additionally confirmed by the selective etching of coating microstructure. The annealing of coatings at 823K resulted in pore disappearance and increased the coating microhardness.
Abstract: Various nitriding methods are applicable, viz.: gas nitriding, nitriding in powders and plasma nitriding which is one the latest nitriding technologies applicable for parts made of constructional and tool steels. A large of motor car products made from iron-based alloying powders has been subjected to plasma nitriding process in order to enhance their surface properties like: hardness and abrasive wear. One of the main problems of chemical heat treatment alloys produced by powder metallurgy technology is their porosity degree. In the experiments Fe-Ni-Cu-Mo and Fe-Mo sintered structural parts modified by boron were made. Boron activates the sintering process which results in their considerable consolidation in the sintering at 1473 K for 60 minutes in the atmosphere of hydrogen. The experiments are related to the production of sintered structural elements based on iron powder - NC 100.24 as well as Astaloy Mo (Fe-Mo) and Distaloy SA (Fe-Ni-Cu-Mo) modified by 0.2 wt%, 0.4 wt% and 0.6 wt% B. Sintered parts were obtained by mixing powders said above, followed by compacting at 600 MPa pressure and sintered at 1473 K during 60 minutes time in hydrogen atmosphere. Selected sintered parts were plasma nitrided at 883 K during 4 hours time. After plasma nitriding microstructure morphology using light microscopy and phase identification by Xray diffraction technique have been made. The influence of structure and phase composition on the surface properties of examined sintered parts modified by boron, after plasma nitriding have been analyzed.
Abstract: In this study, commercial Cu was subjected to plastic deformation by compression with oscillatory torsion. Different deformation parameters were adopted to study their effects on the microstructure and mechanical properties of Cu. The deformed microstructure was characterized by using scanning electron microscopy (SEM) equipment with electron backscattered diffraction (EBSD) facility and scanning transmission electron microscopy (STEM). The mechanical properties were determined on an MTS QTest/10 machine equipped with digital image correlation. Can be found, that process performed at high compression rate and high torsion frequency is recommended for the refining grain size. The size of structure elements: average grain size (D) and subgrain size (d) reached 0.42 m and 0.30 m respectively, and the fraction of high angle boundaries was 35%, when the sample was deformed at a torsion frequency f= 1.6 Hz and compression rate v=0.04 mm/s. Deformation at these parameters leads to an improvement in strength properties. The strength properties are about two times greater than the initial state.
Abstract: Iron phases present in alloys from the 6xxx series affect the workability behaviour of these alloys. Iron in these alloys occurs in the form of intermetallic phases and AlFe, α-AlFeSi, β- AlFeSi eutectics. The homogenisation treatment is carried out to induce the transformation of phase into phase The aim of the studies was EDX and EBSD analysis by scanning microscopy of iron phases present in model alloys based on 6061 system, characterised by the silicon-iron ratio Si/Fe=0,5 and 1, examined in as-cast condition and after homogenisation, followed by a comparison of the detected phases with phases present in industrial ingots. In 6061 alloy, copper in the amount of 0,4wt.% occurred in the solid solution of aluminium. The EDX analysis proved that copper atoms were embedded also in iron precipitates, and scarce phases of an AlxCuy type were being formed. Different content of magnesium in the examined alloys (0,8 and 1,2wt.%) affected not only the quantitative content of Mg2Si phases, but also the presence of AlFe phases in alloy with small content of Si (0,4wt.%) and high content of Mg (1,2wt.%).
Abstract: The present paper is aimed at investigations of mechanical properties and structure of technical purity aluminum powders prepared by plastic consolidation process. The research work is focused on effective improvement of mechanical properties of material while keeping the conductivity at high level. It is well known that application of rapid solidification method with hot extrusion technique leads to grain refinement, as so according to Hall-Petch rule, improvement in mechanical properties of material can be expected. Furthermore, additional material strength can be obtained by aluminum oxides from free surface of powders that became internal boundaries during consolidation process. Aluminum powders atomized by air, argon and water were cold compacted and extruded at temperatures of 325°C and 375°C. For comparison purposes the same extrusion conditions were applied to cast aluminum. In order to analyze effect of recrystalization process during hot extrusion operation, different extrusion temperatures were chosen. Tensile tests as well as micro-hardnes measurements showed significant increase in mechanical strength for RS samples in comparison to conventionally cast material. Structural observations by means of transmission electron microscopy revealed that grain size of materials extruded at the given temperature was at the same level, however amount and distribution of oxides particles differs significantly. It was considered that differences in strength between individual RS material were attributed to this effect.
Abstract: Good mechanical properties with combination of biocompatibility and high corrosion resistance make titanium and its alloys desirable materials for medical applications. A big disadvantage of titanium connects with its poor wear characteristics, however in this work this property was modified by boride microplasma surface alloying. Plasma surface alloying gives a wide range of layer thickness, which is controlled by the amount of the placed powder and process parameters like gas flow, nozzle diameter and current. Formation of TiB phase precipitation was confirmed by XRD analysis. Additionally, the modified microstructure was observed by optical microscopy. The Vickers microhardness was significantly improved from 180HV for original titanium substrate to 900HV in obtained composite layer structure, with a smoth hardness reduction in the cross section profile. Strong heat penetration from microplasma melt-in technique, results in substrate dissolution with formation of stable composite Ti + TiB layer. The surface corrosion resistance in 0.9% NaCl solution was nearly the same as for pure titanium, showing stable behavior of created oxide layer, with no negative effect of dual phase microstructure. Wear resistance of received composite layer structures were significantly improved in comparison with initial titanium samples.