1,721,138 research outputs found
In-situ investigations of interface reactions in metal coated polycrystalline and monocrystalline synthetic diamonds by XRD-phase analysis
No full textDue to their high hardness, synthetic diamonds are used in a wide range of high abrasive applications like machining and grinding. However, diamonds are able to react with metals with a high carbon affinity. The understanding of this behavior is very important if diamonds and metals are in contact at high temperature. This happens for example during the fabrication of diamond-metal composite materials which are mainly used as cutting segments in concrete and natural-stone machining. The heat treatment during the sintering process in powder-metallurgical fabrication routes enforces the formation of layers between the diamond surface and the metal matrix. Such layers directly influence the wear behavior of the diamond tools. In the case of carbide forming elements (Cr or Ti) the diamond retention will be better than in inert metal matrix systems (Cu or Bronze). In this work the carbide forming characteristics of metal (e.g. titanium) coated diamonds, which can be used in inert matrix compositions, will be investigated by means of synchrotron assisted in-situ x-ray diffraction
In-situ investigations of interface reactions in metal coated polycrystalline and monocrystalline synthetic diamonds by XRD-phase analysis
No full textDue to their high hardness, synthetic diamonds are used in a wide range of high abrasive applications like machining and grinding. However, diamonds are able to react with metals with a high carbon affinity. The understanding of this behavior is very important if diamonds and metals are in contact at high temperature. This happens for example during the fabrication of diamond-metal composite materials which are mainly used as cutting segments in concrete and natural-stone machining. The heat treatment during the sintering process in powder-metallurgical fabrication routes enforces the formation of layers between the diamond surface and the metal matrix. Such layers directly influence the wear behavior of the diamond tools. In the case of carbide forming elements (Cr or Ti) the diamond retention will be better than in inert metal matrix systems (Cu or Bronze). In this work the carbide forming characteristics of metal (e.g. titanium) coated diamonds, which can be used in inert matrix compositions, will be investigated by means of synchrotron assisted in-situ x-ray diffraction
Nanostructured WC-Co coatings manufactured by fine powders (-10+2 μm) with ultra-fine carbides (400 nm) by means of HVOF
No full textInfluence of hot pressing and vacuum sintering parameters on interfacial reactions in diamond-metal composites
No full textThe construction industry, especially the machining of natural stone and concrete, as well as the demolition of reinforced concrete structures, places high demands on the wear resistance of the used diamond-metal composite materials, which are attached to wire saws and drill bits. Material characteristics such as the hardness, porosity and the wear behavior of these diamond tools are mainly influenced by the bonding of the diamonds embedded in the metal matrix. In this case, carbide forming metals enforce a strong chemical bonding while catalytically active metals lead to a graphitization on the diamond surface, which weakens the bonding between the diamonds and the matrix. Previous research has revealed the effects of different metal matrix components on the embedded diamonds during the sintering process. Based on these results, this paper will focus on the parameter-dependencies such as the sintering time and temperature in hot-pressing as well as vacuum-sintering processes
Nanostructured WC-Co coatings manufactured by fine powders (-10+2 μm) with ultra-fine carbides (400 nm) by means of HVOF
No full textStructure analysis of the interfacial region between diamonds and metal matrices
No full textDiamond tools have widely established their usage in machining and cutting of hard materials. Although nowadays a multiplicity of specialized diamond tools exist the bonding mechanisms between the embedded diamond particles and the metal matrices are not completely understood. Especially the type and strength of the bonding between diamond and metal is of great relevance for the quality of tools. In this work diamond metal (Co(Cr), FeCu(Cr)) composites have been investigated by X-ray diffraction. The aim was the analysisof the interfacial region between the diamonds and metal matrices showing either metal-carbides or graphite. It is shown that graphitization of the diamond took place if a pure cobalt or an iron-copper matrix was used. By adding chromium to these two metal matrices the graphitization was reduced. Furthermore, the presence of chromium and iron carbides could be proved while cobalt carbide phases could not be detected
Influence of hot pressing and vacuum sintering parameters on interfacial reactions in diamond-metal composites
No full textThe construction industry, especially the machining of natural stone and concrete, as well as the demolition of reinforced concrete structures, places high demands on the wear resistance of the used diamond-metal composite materials, which are attached to wire saws and drill bits. Material characteristics such as the hardness, porosity and the wear behavior of these diamond tools are mainly influenced by the bonding of the diamonds embedded in the metal matrix. In this case, carbide forming metals enforce a strong chemical bonding while catalytically active metals lead to a graphitization on the diamond surface, which weakens the bonding between the diamonds and the matrix. Previous research has revealed the effects of different metal matrix components on the embedded diamonds during the sintering process. Based on these results, this paper will focus on the parameter-dependencies such as the sintering time and temperature in hot-pressing as well as vacuum-sintering processes
Structure analysis of the interfacial region between diamonds and metal matrices
No full textDiamond tools have widely established their usage in machining and cutting of hard materials. Although nowadays a multiplicity of specialized diamond tools exist the bonding mechanisms between the embedded diamond particles and the metal matrices are not completely understood. Especially the type and strength of the bonding between diamond and metal is of great relevance for the quality of tools. In this work diamond metal (Co(Cr), FeCu(Cr)) composites have been investigated by X-ray diffraction. The aim was the analysisof the interfacial region between the diamonds and metal matrices showing either metal-carbides or graphite. It is shown that graphitization of the diamond took place if a pure cobalt or an iron-copper matrix was used. By adding chromium to these two metal matrices the graphitization was reduced. Furthermore, the presence of chromium and iron carbides could be proved while cobalt carbide phases could not be detected
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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