Poznań, Poland
Poznań, Poland

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Jakubowicz J.,Poznan University of Technology | Adamek G.,Poznan University of Technology | Palka K.,Lublin University of Technology | Andrzejewski D.,Metal Forming Institute
Materials Characterization | Year: 2015

The paper describes the formation, morphology and mechanical properties of Ti void composites. The Ti void composites were made using 100 and 325 mesh Ti powder for solid scaffold formation. The spherical and polyhedral voids (pores) were formed using saccharose particles (table sugar) of different shapes. The Ti void composite morphology was investigated by microcomputed tomography and scanning electron microscopy. The Ti void composites of designed porosity of 50-70% were made. Compression test was applied for mechanical properties estimation. It has been found, that Ti void composites made from 100 mesh Ti and those having spherical pores have a higher strength and elastic modulus, i.e. for the designed porosity of 50% for 100 and 325 mesh Ti void composites, a compressive strength was 32.32 and 20.13 MPa, respectively. It has been shown that this is related to better sintering of the 100 mesh Ti powders compared with the 325 mesh Ti powders. A correlation between microcomputed tomography data and mechanical properties has also been shown. The Ti void composites, made with the use of saccharose as a space holder, described in this work should be a promising material for biomedical applications, where interconnected pores and good mechanical properties are required. © 2014 Elsevier Inc. All rights reserved.

Borowski J.,Metal Forming Institute | Bartkowiak K.,Friedrich - Alexander - University, Erlangen - Nuremberg | Bartkowiak K.,Poznan University of Technology
Physics Procedia | Year: 2010

An analysis of the literature concerning the methods of surface treatment of aluminum alloys has been performed. Based on the literature and on earlier initial investigation (hardness measurements, microscopic inspection, roughness measurements, tribological tests and scanning microscope inspection of AlSi6Cu4 and 6082 (PA4) alloy samples exposed to laser, it has been determined that the hardness of the AlSi6Cu4 alloy has increased from the level of 60-80 HV 0.1 to the level of 120 HV 0.5 due to laser treatment, while heat treatment dispersion hardening has resulted in further increase of the hardness of the laser treated zones up to the level of 160 HV. The even structure obtained allows us to propose such technology for increasing hardness and wear resistance of those alloys. In the 6082 alloy, containing less alloy elements, the hardness increase is smaller reaching the level of 120 HV0.5. This is related to obtaining zones with dispersion secretions. The suggested laser treatment parameters, 400W and 530 W with the traverse velocity of 2.8 to 5.33 mm/s do not cause significant increase of roughness, due to which such surface does not require further machining. The results of initial tribological investigation are very promising and they allow us to expect that the technology of structure comminution by laser treatment will allow for improving the life time of products with laser treated surface.

Adamek G.,Poznan University of Technology | Andrzejewski D.,Metal Forming Institute | Jakubowicz J.,Poznan University of Technology
Journal of Biomaterials and Tissue Engineering | Year: 2014

The paper presents a new procedure for void metal composite (VMC) formation. Table sugar crystals (saccharose) as a space holder material that forms voids around Ti scaffold have been used. In the process, the Ti with sugar particles were mixed together and uniaxially pressed to make green compacts composed of the Ti and sugar grains. The voids in the compacts were then made by dissolving sugar crystals in water. Such titanium scaffold was sintered at 1300 _C, and a Ti- VMC was made with homogenously distributed uniform voids of diameter of up to 1 mm. Sugar particles of polyhedral and spherical shape were applied for voids formation and the sugar shape was controlled by the sugar mixing process. Thus, after compacting of the Ti powder with proper sugar crystals, the voids of polyhedral or spherical shape were achieved. The authors show that the compression strength of the Ti-VMC of 75% porosity depends on the shape of the voids and is higher for polyhedral than for spherical sugar spacers, whereas the Young’s modulus is higher for spherical voids. © 2014 American Scientific Publishers. All rights reserved.

Garbiec D.,Metal Forming Institute | Siwak P.,Poznan University of Technology
Powder Metallurgy | Year: 2016

Spark plasma sintering (SPS) has been used to successfully densify a 7075 aluminium alloy obtained from Alumix 431 powder. Sintering experiments were conducted at the temperature of 450 and 500°C for 2.5, 5 and 10 min. All the presented results confirm the excellent sinterability of Alumix 431 powder in vacuum during the SPS process and clearly show the effect of sintering temperatures and holding times on the densification, microstructure and mechanical properties of the obtained sintered compacts. The best results of hardness (1412 ± 39 MPa), tensile strength (345 ± 15 MPa) and compressive strength (618 ± 4 MPa) were obtained by the compacts sintered at 500°C for 5 min. © 2016 Institute of Materials, Minerals and Mining

Walczyk W.,Metal Forming Institute | Milenin A.,AGH University of Science and Technology | Pietrzyk M.,AGH University of Science and Technology
Steel Research International | Year: 2011

Application of numerical simulations to improve forging technology for crank shafts is the objective of this work. Plastometric tests were performed for steels used for manufacturing of crank shafts and a rheological model for these steels was determined. Inverse analysis was applied for the identification of the model parameters. This model was implemented in the finite element software and simulations of various variants of forging were performed. Results of simulations were used to select the best variant, which gives the lowest loses of the material and proper shape of the final product. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wisniewska-Weinert H.,Metal Forming Institute
Archives of Civil and Mechanical Engineering | Year: 2013

Application of solid lubricant nanoparticles to achieve the ultra low friction is proved to be a promising way of tribology development. A new exfoliation based technology of MoS2 solid lubricant nanoparticles is developed and elaborated in this work. The mechanical exfoliation technology of manufacturing MoS2 graphene-like nanoparticles by carefully controlling exfoliation parameters is examined with rolling cleavage machine, and the first characterization of nanoparticle-microparticle mixture obtained by this technology is made. The results reveal the promising application potential of the method. © 2013 Politechnika WrocŁawska.

Wisniewska-Weinert H.,Metal Forming Institute
Powder Metallurgy and Metal Ceramics | Year: 2013

The paper is devoted to analysis of friction and wear of real porous sliding bearings modified with solid lubricant layers at high temperature. For this purpose, a special homemade friction tester was applied. The technology of sleeve nitriding is described. The results of the friction tests reveal about the achievement of quasi-hydrodynamic lubrication regime of powder bearings. The lowest friction coefficient is found to be f = 0.04 at 300 C. The great effect of wear rate diminishing is obtained at 300 C as interaction of microasperities is preserved at the sliding interface in quasi-hydrodynamic lubrication regime. © 2013 Springer Science+Business Media New York.

Borowski J.,Metal Forming Institute | Wendland J.,Metal Forming Institute
Metalurgija | Year: 2016

Extrusion dies are usually regenerated several times (min 4 times). The phenomenon of extended life after each regenerative nitriding process has not been explained. In this work, the regeneration process of dies used in the extrusion of aluminium profiles has been presented. In the article, it was sought to explain the cause of increased die durability after the third or fourth nitriding. Also in this work is presented an analysis of the influence of the parameters of gas nitriding with the ZeroFlow method on hardness of dies. Results were verified under industrial conditions at extrusion company, comparing the durability of the dies nitrided with the ZeroFlow method with so-far-used dies nitrided in the commercial way. An increase of the dies durability was achieved after a single ZeroFlow nitriding. © 2016, Faculty of Metallurgy. All rights reserved.

Wisniewska-Weinert H.,Metal Forming Institute
Archives of Civil and Mechanical Engineering | Year: 2014

With the rapid development of industries and advanced technologies, more and more mechanical devices are required to work at high temperatures. The use of nano- and micro-particle solid lubricants is attracting great attention, particularly for high temperature applications. The structure of the solid lubricant particulate layer together combined with particle functionality determines its performance. The formation of a solid lubricant powder layer with a certain thickness, density and morphology is of great importance to solve the problem of high temperature lubrication. A pressure impregnation/filtering technology is applied for this purpose. The paper describes the phenomena encountered in the pressure filtration operation and defines the parameters of the pressure impregnation technology. © 2013 Politechnika Wroclawska.

Wisniewska-Weinert H.,Metal Forming Institute
Archives of Metallurgy and Materials | Year: 2015

A surface modification of stainless steel bearing sleeves is developed to improve the tribology characteristics at high temperature. Solid lubricant nano- and microparticles are applied for this purpose. To create the quasi-hydrodynamic lubrication regimes, the solid lubricant powder layer is made by developed pressure impregnation technique. Porous sliding bearing sleeve prototypes were made by powder metallurgy technique. The purpose of the paper is to define the friction and wear characteristics of the sleeves and to determine the influence of sealing of the sliding interface on these characteristics. It is found that application of WS2 sold lubricant nano- and micro-particles and preservation of a particle leakage out of interface allows to achieve at the high temperature the friction coefficients comparable to those at ambient temperature.

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