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1

The computer simulation of internal stresses of tool gradient materials reinforced with the WC-Co

Dobrzański L., Kwaśny W., Dołżańska B.

Archives of Materials Science and Engineering

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2012

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Vol. 57, nr 1

38-44

EN

Purpose: The general topic of this paper is the computer simulation with the use of finite element method for determining the internal stresses in tool gradient materials WC-Co obtained in the powder metallurgy process in different temperatures of 1400°C + HIP and 1460°C + HIP. Design/methodology/approach: The following research studies have been carried out a new group of sintered tool gradient materials, tungsten carbide with cobalt matrix, modeling of stresses was performed used of finite elements method in ANSYS environment, and the experimental values of stresses were determined basing on the X-ray diffraction patterns. Findings: The developed model of the tool consists of four layers with different contents of tungsten carbide and the concentration of cobalt by using the finite element method allows to simulate the impact of sintering temperature on the stress occurring in the material. On the basis of the model, it was found that by properly controlled treatment technology, able to induce compressive stresses in the surface layer of material, thus increasing the resistance of the material on the formation and propagation of cracks. Research limitations/implications: It was confirmed that using of finite element method can be a way for Computer simulation of stresses, strains and displacements of the fabricated gradient material depending on the sintering temperature. Results reached in this way are satisfying and in slight degree differ from results reached by experimental method. However for achieving better calculation accuracy in further researches it should be developed given model which was presented in this paper. Originality/value: The obtained results show the possibility to manufacture TGMs on the basis of different portions of cobalt reinforced with hard ceramics particles in order. The computer simulation is based on the finite element method, which allows to better understand the interdependence between parameters of process and choosing optimal solution.

2

Manufacturing technologies of sintered graded tool materials evaluated according to foresight methodology

Dobrzańska-Danikiewicz A., Kloc-Ptaszna A., Dołżańska B.

Archives of Materials Science and Engineering

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2011

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Vol. 50, nr 2

69-97

EN

Purpose: The goal of this paper is to evaluate the development efficiency of conventional technologies of powder metallurgy used for graded tool materials manufacturing. The technologies were divided into three groups according to the matrix type and the percent fraction volume of components in the powders layers. Design/methodology/approach: In the framework of foresight-materials science research a foresight matrices set was created, materials science experiments using light, transmission and scanning electron microscopes, X-ray diffractometer, microhardness tester, work-stands for testing of fatigue resistance, mechanical fatigue strength, fracture toughness were conducted and technology roadmaps were prepared. Findings: Quite high potential and attractiveness of the analysed technologies against the environment, as well as good development perspectives in industry were shown. Research limitations/implications: Research concerning graded tool materials constitute a part of a larger research project aimed at identifying, researching, and characterising the priority innovative technologies in the field of materials surface engineering. Practical implications: The presented materials science results prove a manufacturing possibility of elements with ductile cores and hard coatings using conventional technologies of powder metallurgy. These technologies are recommended for practical implementation in industry, especially for cutting tools. Originality/value: The originality of this paper the value evaluation of manufacturing technologies of graded tool materials against background environment including the influence of the chemical composition and sintering conditions on the surface layers hardness.

3

Characteristics of structure and properties of a sintered graded tool materials with cobalt matrix

Dobrzański L. A., Dołżańska B., Gołombek K., Matula G.

Archives of Materials Science and Engineering

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2011

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Vol. 47, nr 2

69-76

EN

Purpose: The mechanical alloying (MA) method has been chosen to manufacture tool gradient materials with high disproportion of cobalt matrix portion between core and surface layer. Design/methodology/approach: The following research studies have been carried out to elaborate a new group of sintered tool gradient materials, tungsten carbide with cobalt matrix, to elaborate their fabrication technology and to determine their structure and properties: a fabrication technology of mixtures and the formation technology of tungsten carbide gradient materials with cobalt matrix WC-Co was applied and elaborated; sintering conditions were selected experimentally, ensuring the best structure and properties; phase and chemical composition of the sintered gradient WC-Co materials was determined using EDX; the structure of sintered gradient WC-Co materials was investigated using scanning microscopy; mechanical and physical properties of sintered gradient WC-Co materials was determined: hardness, resistance to abrasive wear, resistance to brittle cracking. Findings: The presented research results confirm that the methods of mixing tungsten carbide in cobalt matrix an important effect upon the grain size of mixture. But it is not possible to determine the changes in grain size distribution. The larger particles break down rapidly that the product becomes more uniform. Practical implications: The material presented in this paper is characterized by very high hardness of the surface and relative ductility of the core. Originality/value: The obtained results show the possibility to manufacture TGMs on the basis of different portions of cobalt reinforced with hard ceramics particles in order to improve the abrasive resistance and ductility of tool cutting materials.

4

Structure and properties of sintered tool gradient materials

Dobrzański L. A., Dołżańska B.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 43, nr 2

711--733

EN

Purpose: The main objective of the presented is to elaborate the fabrication technology of novel sintered tool gradient materials on the basis of hard wolfram carbide phase with cobalt binding phase, and to carry out research studies on the structure and properties of the newly elaborated sintered tool gradient materials. Design/methodology/approach: The following research studies have been carried out to elaborate a new group of sintered tool gradient materials, wolfram carbide with cobalt matrix, to elaborate their fabrication technology and to determine their structure and properties: a fabrication technology of mixtures and the formation technology of wolfram carbide gradient materials with cobalt matrix WC-Co was applied and elaborated; sintering conditions were selected experimentally: time, temperature and sintering atmosphere as well as isostatic condensation, ensuring the best structure and properties; phase and chemical composition of the sintered gradient WC-Co materials was determined using EDX, EBSD methods and qualitative X-ray analysis; the structure of sintered gradient WC-Co materials was investigated using scanning microscopy and transmission electron microscopy; mechanical and physical properties of sintered gradient WC-Co materials was determined: porosity, density, hardness, resistance to abrasive wear, resistance to brittle cracking. Findings: The presented research results confirm that the newly elaborated technology of powder metallurgy, which consists in sequential coating of the moulding with layers having the increasing content of carbides and decreasing concentration of cobalt, and then sintering such a compact, ensures the acquisition of the required structure and properties, including the resistance to cracking and abrasive wear of tool gradient materials, due to earned high hardness and resistance to abrasive wear on the surface as well as high resistance to cracking in the core of the materials fabricated in such a way. Practical implications: The material presented in this paper is characterized by very high hardness of the surface and relative ductility of the core. TGM with smooth changes of the cobalt phase in the material. Originality/value: The obtained results show the possibility to manufacture TGMs on the basis of different portions of cobalt reinforced with hard ceramics particles in order to improve the abrasive resistance and ductility of tool cutting materials.

5

Hardness to toughness relationship on WC-Co tool gradient materials evaluated by Palmqvist method

Dobrzański L., Dołżańska B.

Archives of Materials Science and Engineering

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2010

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Vol. 43, nr 2

87-93

EN

Purpose: Goal of this work was to describe the propagation characteristic of cracks produced at the corners of Vickers indent and the toughness change in functionally graded WC-Co cemented carbide with high disproportion of cobalt matrix portion between core and surface layer. Design/methodology/approach: Investigations of toughness methods were developed during the investigations for tungsten carbide and cobalt, making it possible to obtain four materials and then their structure was determined. Findings: A wide variation in hardness and toughness has been obtained in WC-Co composites. The propagation characteristic of cracks produced at the corners of Vickers indent and the toughness change in functionally graded WC-Co cemented carbide with dual phase structure were investigated. It is shown that cracks tend to propagate both around and across WC crystal grain. The changes of toughness with the microstructure and an integrated strengthening effect, as well as high toughness characteristic of the tool gradient material are revealed. Practical implications: Material presented in this paper are characterized by very high hardness of the surface and relative ductility of core. The cobalt phase in obtained TGM material will changing smoothly. Originality/value: The Palmqvist test provides a useful method of measuring fracture toughness of material characterized by very high hardness of the surface and relative ductility of core.

6

Structure and properties of tool gradient materials reinforced with the WC carbides

Dobrzański L. A., Dołżańska B., Matula G.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 28, nr 1

35-38

EN

Purpose: The purpose of the paper is to describe sintered Tool Gradient Materials manufactured by powder metallurgy process. The Powder Metallurgy method has been chosen to manufacture tool gradient materials with high disproportion of cobalt matrix portion between core and surface layer. Design/methodology/approach: Forming methods were developed during the investigations for tungsten carbide and cobalt, making it possible to obtain materials wits five layers in their structure. Findings: High diversification of cobalt matrix portion in comparison to hard phases in subsequent layers of gradient materials leads to their deformation in as sintered state. In case of all gradient materials, mean hardness was equal about 1750 HV1. Whereas, hardness of lower cobalt matrix rich layers is about 1548 HV1 and increased up to 2154 HV1 for lower layer of material rich with hard carbide phases. The porosity decreases along with the carbon content in these layers. Practical implications: Material presented in this paper is characterized by very high hardness of the surface and relative ductility of core. TGM with a smooth changes of the cobalt phase in the material. Originality/value: The obtained results show the possibility of manufacturing of TGM on basis of different portion of cobalt reinforced with hard ceramics particles carried out in order to improve the abrasion resistance and ductility of tool cutting materials.

7

Structure and properties of TGM manufactured on the basis of cobalt

Matula G., Dobrzański L. A., Dołżańska B.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 20, nr 1-2

151-154

EN

Purpose: It has been demonstrated in the paper structure and properties of tool gradient materials manufactured by powder metallurgy on the basis of cobalt. Design/methodology/approach: Light microscope, SEM, image analysis, microhardness tests, density examination. Findings: Basing on the investigations of the cemented carbides reinforced with different ceramics particles fabricated it was found of that density of sintered samples depend on reinforced particles, temperatures and atmosphere of sintering. Increasing of sintering temperature increase the density of sintering samples. Moreover the sintering under vacuum atmosphere produce samples with higher quality than using argon atmosphere and prevent of surface oxidation during sintering. Practical implications: The Powder Metallurgy gives the possibility to manufacturing tools gradient materials on the basis of cobalt which characterised very high hardness on the surface. Originality/value: In the paper the manufacturing of tool gradient materials on basis of cobalt reinforced with hard ceramics particles carried out in order to improve the tool cutting properties.

8

Influence of hard ceramic particles on structure and properties of TGM

Dobrzański L. A., Dołżańska B., Matula G.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 24, nr 2

95-98

EN

Purpose: The Powder Metallurgy route has been chosen to fabricate tool gradient materials with high disproportion of cobalt matrix portion between core and surface layer. In the paper structure and properties of TGM have been shown. Design/methodology/approach: SEM, light microscope, microhardness tests, density examination. Findings: According to carried out researches it could be stated, that forming the gradient materials with highest amount of complex carbide (W,Ti)C 90-95%, using uniaxial unilateral pressing, could be possible after adding into each layer of mixes 2 % of paraffin lubricant. High diversification of cobalt matrix ratio in comparison to hard phases in subsequent layers of gradient materials leads to their deformation in as sintered state. In case of all gradient materials, mean hardness was equal about 1600 HV1. Whereas, hardness of lower cobalt matrix rich layers brought values about 1450 HV1 and increased up to 1800 HV1 for lower layer of material rich with hard carbide phases. Practical implications: Material presented in this paper is characterized by very high hardness of the surface and relative ductility of core. TGM is a smoothly varying distribution of phases element composition. Originality/value: In the paper the manufacturing of TGM on basis of different portion of cobalt reinforced with hard ceramics particles carried out in order to improve the abrasion resistance and ductility of tool cutting materials.

9

Influence of carbide (W, Ti)C on the structure and properties of tool gradient materials

Dobrzański L. A., Dołżańska B., Matula G.

Archives of Materials Science and Engineering

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2007

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Vol. 28, nr 10

617-620

EN

Purpose: The goal of this work is to obtain the gradient materials based on the (W, Ti)C with high disproportion of cobalt matrix portion between core and surface layer. In this work is shown the structure and properties of Tool Gradient Materials (TGM). Design/methodology/approach: In presented study (W, Ti)C powder were mixed with cobalt powder. Prepared mixtures were heaped up, pressed at 300MPa and sintered in vacuum furnace at temperatures 1450*C. Produced gradient materials were studied by scanning electron microscope (SEM), light microscope. Hardness tests and density examination were also made. Findings: According to carried out researches it could be stated, that forming the gradient materials with highest portion of complex carbide (W,Ti)C 91-95%, using uniaxial unilateral pressing, could be possible after adding into each layer of mixtures 2% of paraffin lubricant. High diversification of cobalt matrix ratio in comparison with hard phases in subsequent layers of gradient materials leads to their deformation in as sintered state. In case of all gradient materials, mean hardness was equal about 1600 HV1. Whereas, hardness of lower cobalt matrix rich layers has value about 1450 HV1 which increases up to 1700 HV1 for lower layer of material rich with hard carbide phases. Practical implications: The Powder Metallurgy gives the possibility of manufacturing tools gradient materials characterised by very high hardness on the surface and relative ductility in core. Originality/value: In the work the manufacturing of TGM on the basis of different portion of cobalt matrix reinforced with hard ceramics particles carried out in order to improve the abrasion resistance and ductility of tool cutting materials.

10

Comparison of electrical characteristics of silicon solar cells

Dobrzański L. A., Wosińska L., Dołżańska B., Drygała A.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 18, nr 1-2

215--218

EN

Purpose: The aim of this work is comparison of the operational characteristics of photovoltaic silicon cells: monocrystalline silicon, polycrystalline silicon and amorphous silicon. Design/methodology/approach: The notion of fill factor (FF), which is characteristic for Photovoltaic quality, has been introduced to compare properties of different silicon solar cells. Basing on the indicated characteristic the analysis of cell power efficiency has been carried out and the maximum power points PMM have been determined. Findings: It has been pointed out that crystal structure and surface texture affect utility properties of the investigated Photovoltaic Silicon Cells. Moreover, it has been stated that along with the radiation intensity growth the maximum cell power increases accompanied by its efficiency deterioration and simultaneous change of the maximum power point position, what causes and short-circuit current increase. Research limitations/implications: It has been found that the cell surface texture has an important influence on utility properties of the photovoltaic cells, which is connected with the high refractivity of silicon. Therefore, development of the cell surface forming methods is of a significant influence on improvement of the photovoltaic cells properties. Practical implications: Currently the photovoltaic industry is based mostly on the crystalline and polycrystalline silicon. Limitations of the utility properties resulting from the relationships presented in this paper accompany the advantages of cells fabricated from the amorphous and polycrystalline silicon, like the low manufacturing costs and no geometrical limitations. Analysis of the discussed relationships makes optimization of the cel parameters possible, depending on the service requirements. Originality/value: Known cells were compared as regards their conversion efficiency in various lighting conditions, depending on their design and material properties.