This paper discusses the development of silicon carbide (SiC) composite powders for HVOF spraying... more This paper discusses the development of silicon carbide (SiC) composite powders for HVOF spraying. It describes the material properties of various carbides, examines the morphology of SiC powders, and presents the HVOF parameters typically used to spray SiC composite coatings. It also examines the microstructure and composition of SiC nickel and cobalt-base composite coatings and investigates their corrosion and wear behaviors. Paper includes a German-language abstract.
Different post treatment methods such as heat treatment, mechanical processing, sealing, etc. are... more Different post treatment methods such as heat treatment, mechanical processing, sealing, etc. are known to be capable to improve microstructure and exploitation properties of thermal spray coatings. In this work a plasma electrolytic oxidation of aluminium coatings obtained by arc spraying on aluminium and carbon steel substrates is carried out. Microstructure and properties of oxidised layers formed on sprayed coating as well as on bulk material are investigated. Oxidation is performed in electrolyte containing KOH and liquid glass under different process parameters. It is shown that thick uniform oxidised layers can be formed on arc sprayed aluminium coatings as well as on solid material. Distribution of alloying elements and phase composition of obtained layers are investigated. A significant improvement of wear resistance of treated layers in two types of abrasive wear conditions is observed.
Abstract: The amendment of the Drinking Water Directive has reduced the permissible nickel ion co... more Abstract: The amendment of the Drinking Water Directive has reduced the permissible nickel ion content in drinking water from 50 μg/l to 20 μg/l. The development of draft standards has begun on a European level so that national standards can be adjusted and transformed to meet European and international standards. For example, DIN EN 15664-1, valid since June 2008, regulates the influence of metallic materials on water intended for human consumption. Since heat exchangers joined with nickel-based filler metals are applied in the equipment for drinking water systems, there is a possible risk of exceeding the limits for nickel ions. So far, components joined with nickelbased filler metals have been applied according to the 5% rule defined in DIN 50930-6. Under the present circumstances, the ban on nickel-based filler metals as a result of the amendment of the Drinking Water Directive will cause severe economic losses for the suppliers of solders as well as for customers. Nickelbased filler metals have not yet been included in the list of harmless materials. Investigations on the release of nickel ions into drinking water carried out according to DIN EN 15664-1 are presented. These investigations are one step forward for the inclusion of nickel-based filler metals in the list of harmless materials. Further measures, which will also be reported in this contribution, have to be taken.
The use of embedded sensors and actuators for condition assessment of machines and structures is ... more The use of embedded sensors and actuators for condition assessment of machines and structures is on rising demand [1]. Composite parts with high demands on safety and a long economic life-time, e. g. parts in airplanes and blades of wind turbines, will be equipped with strain and impact sensitive sensors in future to monitor their load history. This will lead to a better understanding and a safer application of composite materials. Different types of sensors based on different physical effects are available. Carbon fibre surfaces coated with magnetoelastic materials and structured by methods of micro-manufacturing can serve as strain- and tension-sensitive microsensor systems capable of supporting safety and health monitoring functions in parts made of composite materials. The fabrication method based on thin-film deposition technology and microstructuring by means of Focused Ion Beam (FIB) machining was developed. Carbon fibres with multiple layers deposited by physical or chemical...
HVOF has reached high industrial acceptance for the production of wear and corrosion protective c... more HVOF has reached high industrial acceptance for the production of wear and corrosion protective coatings based on cermets (e.g. WC-Co). With respect to increasing demands on technical surfaces modern research aims to reduce the weight of the sprayed volume and to improve the coating properties with simultaneous reduction of manufacturing costs for feedstock materials. As SiC combines outstanding mechanical, thermal and chemical properties, it is of high interest for thermal spray applications. Up to now thermal spraying of SiC was considered to be impossible, because of its decomposition at elevated temperatures. The development of suitable matrix alloys as metallic binders for composite feedstock enables the production of SiC containing thermal sprayed coatings. The publication presents the metallurgical concept and the results of the investigations on feedstock production processes and thermal spraying of the SiC cermets. The coatings are characterized concerning porosity and SiC ...
Herkommliche Bauteile aus Formgedachtnislegierungen (FGLn) werden vorwiegend durch Weiterverarbei... more Herkommliche Bauteile aus Formgedachtnislegierungen (FGLn) werden vorwiegend durch Weiterverarbeitung von Halbzeugen wie z.B. Stabe, Drahte, Rohren und Platten oder pulvermetallurgisch hergestellt. Insbesondere die wirtschaftliche Herstellung von komplexen und dunnwandigen Teilen erfordert eine entsprechende Technologie. Das thermische Spritzen eroffnet Moglichkeiten dunnwandige Teile aus legiertem Pulver direkt herzustellen. Ni-Ti FGLn zeigen insbesondere bei erhohten Temperaturen eine zunehmende Affinitat zu Sauerstoff, Wasserstoff und Stickstoff; damit verbundene Reaktionen beeintrachtigen oder unterdrucken den Formgedachtniseffekt bzw. die superelastischen Eigenschaften. Die Vakuum Plasma Spritztechnologie (VPS) bietet den Vorteil der Verarbeitung hochreaktiver Werkstoffe unter kontrollierten atmospharischen Bedingungen. Aus diesem Grund wurde die VPS Technologie im Rahmen der Untersuchungen zur Herstellung freitragender Teile aus Ni55.8Ti (Gew.-%) angewendet. Mechanische und st...
Serious damage occurs sporadically in gas-carburizing furnaces employed in the gear manufacturing... more Serious damage occurs sporadically in gas-carburizing furnaces employed in the gear manufacturing industry if the cast grate sticks to the skid rail. The sticking is caused by hardening salts and/or detergents left in the furnace from earlier hardening operations. Components of these salts and/or detergents form a glassy-like surface on the skid rails which causes sticking to the cast grates. This effect is influenced by low porosity of the slide rings.
The industrial progress and the market-oriented management concepts result in increasing demands ... more The industrial progress and the market-oriented management concepts result in increasing demands of the industry for improved performances while simultaneously improving on the energy efficiency. This results in the necessity for a progressive implementation of high-performance materials in areas such as the automotive industry, engineering, as well as applications in aerospace industry. Especially construction elements taking on large stresses call for excellent mechanical properties even at extremely high temperatures. In these high-temperature ranges only engineering ceramics, which unfortunately are very limited regarding the application due to the very brittle characteristics, showcase sufficient strength values.
The main tendencies in the development of tungsten carbide coating applications are presented. Ge... more The main tendencies in the development of tungsten carbide coating applications are presented. General properties of WC based coatings and their dependence on different factors are discussed. For comparative examination of the abrasive wear resistance of thermal spray coatings detailed Taber Abraser wear tests are carried out. Besides HVOF sprayed cermet and APS Cr 2 O 3 also electroplated hard chromium coatings are studied. The best results have been obtained for HVOF sprayed cermet coatings. For this kind of wear conditions the difference in wear behaviour depending on carbide size in WC-CoCr coatings is insignificant compared to the difference depending on the matrix composition.
In Hybridlaminaten werden die positiven Eigenschaften metallischer und faserverstärkter polymerer... more In Hybridlaminaten werden die positiven Eigenschaften metallischer und faserverstärkter polymerer Komponenten miteinander kombiniert. Vorteile der thermoplastischen Kunststoffkomponente, wie z. B. Umformbarkeit und Recyclingfähigkeit sowie Großserientauglichkeit, bieten einen herausragenden Vorteil gegenüber duroplastischen Matrices. Zur Herstellung der Hybridlaminate werden in einem ersten Schritt Endlosfasern und Thermoplastfolien zu unidirektional faserverstärkten Tapes vorkonsolidiert. Anschließend werden diese belastungsgerecht mit der metallischen Komponente verpresst, wobei das Interface zwischen faserverstärktem Thermoplast und der metallischen Folie eine entscheidende Rolle spielt. Im vorliegenden Beitrag werden Hybridlaminate mit kohlenstofffaserverstärktem Polyamid (CF-PA6) als Kernschichten und glasfaserverstärktem Polyamid (GF-PA6) als Zwischenschicht zur metallischen Komponente untersucht. Bei den Laminaten kommt ein 2/1-sowie 3/2-Aufbau mit zwei bzw. drei Metalllagen sowie einer bzw. zwei Lagen faserverstärkten Kunststoffes zum Einsatz. Als metallische Folie werden die Aluminiumlegierung EN AW-6082 und die Titanlegierung Ti3Al2,5V (Grade 9) verwendet. Die Laminatherstellung, die Entwicklung und die Einstellung des Interfaces sowie die Evaluierung der mechanischen Eigenschaften werden im Beitrag diskutiert.
Interfacial Phenomena in Composite Materials '91, 1991
Metallic and ceramic materials were sprayed using atmospheric arc (Ni and Mo on mild steel and Fe... more Metallic and ceramic materials were sprayed using atmospheric arc (Ni and Mo on mild steel and Fe) and plasma (Al2O3 on NiCr20 substrate) spraying techniques. The aim of the investigations was to analyse the interfacial phenomena and particle microstructure and morphology. The phase composition of sprayed particles and substrates in the interface area was investigated by optical and electron microscopical (SEM, TEM) methods. The bond quality was also determined by bond strength measurements. It is possible to correlate the results of microscopical investigations of interface phenomena with results of quantitatively measured bond strength of plasma sprayed Ni coatings.
ABSTRACT Carbon fibres are fabricated in bundles. A single roving contains a minimum of 1000 fila... more ABSTRACT Carbon fibres are fabricated in bundles. A single roving contains a minimum of 1000 filaments. Certain applications demand thinner bundles or even single fibres. Single fibres can be used as tool electrodes in electrochemical machining processes. Thinner rovings are needed in sensor applications to raise the electrical resistance of the carbon fibre bundle used as strain sensor. Rovings with a lower filament count cannot be delivered by carbon fibre producers. A splitting technology is therefore needed. A continuous bundle splitting technique was developed. It uses mechanical means, liquid flow and variations in winding force and speed to separate the filaments. The impact of winding parameters and of the liquid flow on the splitting result was quantified in experiments with the developed splitting system. An automatic and continuous splitting of carbon fibre rovings was realised. Smaller bundles of carbon fibre filaments can be provided. There is a solution to satisfy the demand on finer carbon fibre rovings.
Electroplated nickel coatings provide ductility, excellent corrosion resistance and good wear res... more Electroplated nickel coatings provide ductility, excellent corrosion resistance and good wear resistance, which qualifies them to meet complex demands of engineering, microtechnology and microelectronics. The co-deposition of particles is a promising alternative to deposit layers with adequate microstructure and properties avoiding the rise of residual stress. The incorporation of the sufficient quantity of particles, monodisperse distribution and downsizing to nanometre scale affect the amount of strengthening by dispersion hardening. To avoid agglomeration in the electroplating bath as well as in the layer is a challenge which has been met by simple Watts nickel electrolyte with a minimum of organic additives and adequate bath agitation comprising sonication, i.e. the exposure of the bath to high-frequency sound waves. Well-dispersed hard particles (titanium oxide and silicon carbide) were incorporated in nickel films. The focus was set on the correlation between the gained micros...
This paper discusses the development of silicon carbide (SiC) composite powders for HVOF spraying... more This paper discusses the development of silicon carbide (SiC) composite powders for HVOF spraying. It describes the material properties of various carbides, examines the morphology of SiC powders, and presents the HVOF parameters typically used to spray SiC composite coatings. It also examines the microstructure and composition of SiC nickel and cobalt-base composite coatings and investigates their corrosion and wear behaviors. Paper includes a German-language abstract.
Different post treatment methods such as heat treatment, mechanical processing, sealing, etc. are... more Different post treatment methods such as heat treatment, mechanical processing, sealing, etc. are known to be capable to improve microstructure and exploitation properties of thermal spray coatings. In this work a plasma electrolytic oxidation of aluminium coatings obtained by arc spraying on aluminium and carbon steel substrates is carried out. Microstructure and properties of oxidised layers formed on sprayed coating as well as on bulk material are investigated. Oxidation is performed in electrolyte containing KOH and liquid glass under different process parameters. It is shown that thick uniform oxidised layers can be formed on arc sprayed aluminium coatings as well as on solid material. Distribution of alloying elements and phase composition of obtained layers are investigated. A significant improvement of wear resistance of treated layers in two types of abrasive wear conditions is observed.
Abstract: The amendment of the Drinking Water Directive has reduced the permissible nickel ion co... more Abstract: The amendment of the Drinking Water Directive has reduced the permissible nickel ion content in drinking water from 50 μg/l to 20 μg/l. The development of draft standards has begun on a European level so that national standards can be adjusted and transformed to meet European and international standards. For example, DIN EN 15664-1, valid since June 2008, regulates the influence of metallic materials on water intended for human consumption. Since heat exchangers joined with nickel-based filler metals are applied in the equipment for drinking water systems, there is a possible risk of exceeding the limits for nickel ions. So far, components joined with nickelbased filler metals have been applied according to the 5% rule defined in DIN 50930-6. Under the present circumstances, the ban on nickel-based filler metals as a result of the amendment of the Drinking Water Directive will cause severe economic losses for the suppliers of solders as well as for customers. Nickelbased filler metals have not yet been included in the list of harmless materials. Investigations on the release of nickel ions into drinking water carried out according to DIN EN 15664-1 are presented. These investigations are one step forward for the inclusion of nickel-based filler metals in the list of harmless materials. Further measures, which will also be reported in this contribution, have to be taken.
The use of embedded sensors and actuators for condition assessment of machines and structures is ... more The use of embedded sensors and actuators for condition assessment of machines and structures is on rising demand [1]. Composite parts with high demands on safety and a long economic life-time, e. g. parts in airplanes and blades of wind turbines, will be equipped with strain and impact sensitive sensors in future to monitor their load history. This will lead to a better understanding and a safer application of composite materials. Different types of sensors based on different physical effects are available. Carbon fibre surfaces coated with magnetoelastic materials and structured by methods of micro-manufacturing can serve as strain- and tension-sensitive microsensor systems capable of supporting safety and health monitoring functions in parts made of composite materials. The fabrication method based on thin-film deposition technology and microstructuring by means of Focused Ion Beam (FIB) machining was developed. Carbon fibres with multiple layers deposited by physical or chemical...
HVOF has reached high industrial acceptance for the production of wear and corrosion protective c... more HVOF has reached high industrial acceptance for the production of wear and corrosion protective coatings based on cermets (e.g. WC-Co). With respect to increasing demands on technical surfaces modern research aims to reduce the weight of the sprayed volume and to improve the coating properties with simultaneous reduction of manufacturing costs for feedstock materials. As SiC combines outstanding mechanical, thermal and chemical properties, it is of high interest for thermal spray applications. Up to now thermal spraying of SiC was considered to be impossible, because of its decomposition at elevated temperatures. The development of suitable matrix alloys as metallic binders for composite feedstock enables the production of SiC containing thermal sprayed coatings. The publication presents the metallurgical concept and the results of the investigations on feedstock production processes and thermal spraying of the SiC cermets. The coatings are characterized concerning porosity and SiC ...
Herkommliche Bauteile aus Formgedachtnislegierungen (FGLn) werden vorwiegend durch Weiterverarbei... more Herkommliche Bauteile aus Formgedachtnislegierungen (FGLn) werden vorwiegend durch Weiterverarbeitung von Halbzeugen wie z.B. Stabe, Drahte, Rohren und Platten oder pulvermetallurgisch hergestellt. Insbesondere die wirtschaftliche Herstellung von komplexen und dunnwandigen Teilen erfordert eine entsprechende Technologie. Das thermische Spritzen eroffnet Moglichkeiten dunnwandige Teile aus legiertem Pulver direkt herzustellen. Ni-Ti FGLn zeigen insbesondere bei erhohten Temperaturen eine zunehmende Affinitat zu Sauerstoff, Wasserstoff und Stickstoff; damit verbundene Reaktionen beeintrachtigen oder unterdrucken den Formgedachtniseffekt bzw. die superelastischen Eigenschaften. Die Vakuum Plasma Spritztechnologie (VPS) bietet den Vorteil der Verarbeitung hochreaktiver Werkstoffe unter kontrollierten atmospharischen Bedingungen. Aus diesem Grund wurde die VPS Technologie im Rahmen der Untersuchungen zur Herstellung freitragender Teile aus Ni55.8Ti (Gew.-%) angewendet. Mechanische und st...
Serious damage occurs sporadically in gas-carburizing furnaces employed in the gear manufacturing... more Serious damage occurs sporadically in gas-carburizing furnaces employed in the gear manufacturing industry if the cast grate sticks to the skid rail. The sticking is caused by hardening salts and/or detergents left in the furnace from earlier hardening operations. Components of these salts and/or detergents form a glassy-like surface on the skid rails which causes sticking to the cast grates. This effect is influenced by low porosity of the slide rings.
The industrial progress and the market-oriented management concepts result in increasing demands ... more The industrial progress and the market-oriented management concepts result in increasing demands of the industry for improved performances while simultaneously improving on the energy efficiency. This results in the necessity for a progressive implementation of high-performance materials in areas such as the automotive industry, engineering, as well as applications in aerospace industry. Especially construction elements taking on large stresses call for excellent mechanical properties even at extremely high temperatures. In these high-temperature ranges only engineering ceramics, which unfortunately are very limited regarding the application due to the very brittle characteristics, showcase sufficient strength values.
The main tendencies in the development of tungsten carbide coating applications are presented. Ge... more The main tendencies in the development of tungsten carbide coating applications are presented. General properties of WC based coatings and their dependence on different factors are discussed. For comparative examination of the abrasive wear resistance of thermal spray coatings detailed Taber Abraser wear tests are carried out. Besides HVOF sprayed cermet and APS Cr 2 O 3 also electroplated hard chromium coatings are studied. The best results have been obtained for HVOF sprayed cermet coatings. For this kind of wear conditions the difference in wear behaviour depending on carbide size in WC-CoCr coatings is insignificant compared to the difference depending on the matrix composition.
In Hybridlaminaten werden die positiven Eigenschaften metallischer und faserverstärkter polymerer... more In Hybridlaminaten werden die positiven Eigenschaften metallischer und faserverstärkter polymerer Komponenten miteinander kombiniert. Vorteile der thermoplastischen Kunststoffkomponente, wie z. B. Umformbarkeit und Recyclingfähigkeit sowie Großserientauglichkeit, bieten einen herausragenden Vorteil gegenüber duroplastischen Matrices. Zur Herstellung der Hybridlaminate werden in einem ersten Schritt Endlosfasern und Thermoplastfolien zu unidirektional faserverstärkten Tapes vorkonsolidiert. Anschließend werden diese belastungsgerecht mit der metallischen Komponente verpresst, wobei das Interface zwischen faserverstärktem Thermoplast und der metallischen Folie eine entscheidende Rolle spielt. Im vorliegenden Beitrag werden Hybridlaminate mit kohlenstofffaserverstärktem Polyamid (CF-PA6) als Kernschichten und glasfaserverstärktem Polyamid (GF-PA6) als Zwischenschicht zur metallischen Komponente untersucht. Bei den Laminaten kommt ein 2/1-sowie 3/2-Aufbau mit zwei bzw. drei Metalllagen sowie einer bzw. zwei Lagen faserverstärkten Kunststoffes zum Einsatz. Als metallische Folie werden die Aluminiumlegierung EN AW-6082 und die Titanlegierung Ti3Al2,5V (Grade 9) verwendet. Die Laminatherstellung, die Entwicklung und die Einstellung des Interfaces sowie die Evaluierung der mechanischen Eigenschaften werden im Beitrag diskutiert.
Interfacial Phenomena in Composite Materials '91, 1991
Metallic and ceramic materials were sprayed using atmospheric arc (Ni and Mo on mild steel and Fe... more Metallic and ceramic materials were sprayed using atmospheric arc (Ni and Mo on mild steel and Fe) and plasma (Al2O3 on NiCr20 substrate) spraying techniques. The aim of the investigations was to analyse the interfacial phenomena and particle microstructure and morphology. The phase composition of sprayed particles and substrates in the interface area was investigated by optical and electron microscopical (SEM, TEM) methods. The bond quality was also determined by bond strength measurements. It is possible to correlate the results of microscopical investigations of interface phenomena with results of quantitatively measured bond strength of plasma sprayed Ni coatings.
ABSTRACT Carbon fibres are fabricated in bundles. A single roving contains a minimum of 1000 fila... more ABSTRACT Carbon fibres are fabricated in bundles. A single roving contains a minimum of 1000 filaments. Certain applications demand thinner bundles or even single fibres. Single fibres can be used as tool electrodes in electrochemical machining processes. Thinner rovings are needed in sensor applications to raise the electrical resistance of the carbon fibre bundle used as strain sensor. Rovings with a lower filament count cannot be delivered by carbon fibre producers. A splitting technology is therefore needed. A continuous bundle splitting technique was developed. It uses mechanical means, liquid flow and variations in winding force and speed to separate the filaments. The impact of winding parameters and of the liquid flow on the splitting result was quantified in experiments with the developed splitting system. An automatic and continuous splitting of carbon fibre rovings was realised. Smaller bundles of carbon fibre filaments can be provided. There is a solution to satisfy the demand on finer carbon fibre rovings.
Electroplated nickel coatings provide ductility, excellent corrosion resistance and good wear res... more Electroplated nickel coatings provide ductility, excellent corrosion resistance and good wear resistance, which qualifies them to meet complex demands of engineering, microtechnology and microelectronics. The co-deposition of particles is a promising alternative to deposit layers with adequate microstructure and properties avoiding the rise of residual stress. The incorporation of the sufficient quantity of particles, monodisperse distribution and downsizing to nanometre scale affect the amount of strengthening by dispersion hardening. To avoid agglomeration in the electroplating bath as well as in the layer is a challenge which has been met by simple Watts nickel electrolyte with a minimum of organic additives and adequate bath agitation comprising sonication, i.e. the exposure of the bath to high-frequency sound waves. Well-dispersed hard particles (titanium oxide and silicon carbide) were incorporated in nickel films. The focus was set on the correlation between the gained micros...
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