Sealless rolling bearings for use under media lubricated conditions are exposed to high tribocorr... more Sealless rolling bearings for use under media lubricated conditions are exposed to high tribocorrosive loads. To achieve the necessary wear resistance while keeping up the corrosion properties of the corrosion resistant steels low-temperature-plasma-diffusion-treatments were conducted. When scaling-up the developed low-temperature-plasma-nitriding-processes to industrial dimensions, it is necessary to reach the required surface conditions independently of the parts placement within the batch. Upscaling to industrial batch processes was analyzed by using the example of rolling bearings. To achieve a homogeneous treatment result, relevant factors like temperature distribution and component placement were taken into account. This allows to draw conclusions about the surface layer properties in dependence of temperature, batch arrangement and position within the batch to verify the treatment results homogeneity.
Forging tools are often showing short lifetimes compared to cold forming tools e.g. for sheet met... more Forging tools are often showing short lifetimes compared to cold forming tools e.g. for sheet metal forming. This is based on the process conditions where high local surface temperatures are alternating with chilling conditions due to the spray cooling with water based cooling lubricants. The resulting thermal shock is provoking fatigue of the tool material in the near surface regions. Crack initiation and crack growth due to thermal shock exposure then causes chipping of the tool steel material in the surface regions. These are starting points for extensive wear.Hardness and wear resistance of tool surfaces at elevated temperatures can be dramatically enhanced with nitriding pretreatments. This has become state-of-the-art for hot forming tool steels in many forging applications. With inappropriate adjustments of the nitriding parameters a decrease of the ductility can occur and will reduce the crack resistance of the tool surface especially under thermal shock conditions.The hot working steel DIN-1.2367 (X38CrMoV5) is currently one of the most often used chromium–molybdenum tool steels in the field of forging. Exemplary for this material is the influence of the nitriding parameters like temperature, nitrogen supply and plasma parameters on the nitriding depth, the maximum hardness and the crack sensitivity will be discussed.Nitrided samples will be investigated with methods developed for the adhesion measurement of hard coatings. It could be shown that this is also appropriate for a qualification of the crack sensitivity of tools. Comparative application tests in the production of automotive components show the influence on the wear behavior and lifetime of forging tools in an industrial environment.
Metal containing carbon films (a-C:H:Me) have very good tribological properties especially in red... more Metal containing carbon films (a-C:H:Me) have very good tribological properties especially in reducing the friction coefficient in addition to wear and adhesion reduction. Typical metals for this kind of coatings are tungsten, titanium or chrom. Beside these materials other metals, like zirconium, also offer a good option for reducing the friction coefficient or wear. The main problem of these films is that at temperatures higher than 300°C the usability is reduced because of degradation of the coatings due to graphitization and oxidation effects. The a-C:H:Zr-films were prepared by reactive d.c. magnetron sputtering in an argon/acetylene atmosphere with two zirconium targets. The tribological film properties were investigated by nanohardnes, pin on disk, wear and scratch tests. To identify the film characteristics at higher temperatures, samples were tempered at normal atmospheric pressure at 150°C to 550 °C for 1.5 hours. A polished 1.3343 steel was used as the substrate. The resu...
Die vorliegende Erfindung bezieht sich auf die Bereitstellung von Bauteilen fur Gaseinspritzsyste... more Die vorliegende Erfindung bezieht sich auf die Bereitstellung von Bauteilen fur Gaseinspritzsysteme und/oder Verbrennungsmotoren, welche eine geringe Storanfalligkeit und eine lange Standzeit aufweisen. Dazu werden die Bauteile, welche mit Flussig- oder Erdgas in Beruhrung kommen, zumindest an den Bereichen, welche mit Gas in Kontakt sind, beschichtet. Die Beschichtung zeichnet sich dabei durch eine hohe Verschleisfestigkeit, hohe Korrosionsfestigkeit, gunstige Reibungseigenschaften und eine gute AntI-Haftwirkung aus.
Duplex stainless steel is common in thick-walled components such as longitudinal welded pipes in ... more Duplex stainless steel is common in thick-walled components such as longitudinal welded pipes in the oil and gas industries and as parts of various machines in the chemical and food industries. Electron beam welding is a very suitable method for welding such components. Due to the high power density of the electron beam combined with the decreased evaporation temperature in a vacuum atmosphere, steel with a sheet thickness of up to 150 mm can be welded in one pass. In the case of the electron beam welding of duplex stainless steels, vacuum atmosphere in the working chamber causes a nitrogen effusion from the weld pool. The microstructure of the resulting weld is characterized by an unacceptable high ferrite content, which is the main reason for both low impact toughness and low pitting corrosion resistance. This work focuses on the influence of nitrided weld edge surfaces on metallurgical properties of the resulting welded joint. The aim here is to investigate the effect of increase...
ABSTRACT Beside its conventional applications such as improving the wear resistance of machine pa... more ABSTRACT Beside its conventional applications such as improving the wear resistance of machine parts and tools, plasma thermochemical treatment (PTT) can be successfully used as a method for surface modification to achieve specific surface properties. Surface electrical conductivity of austenitic stainless steel sheets, for example, can be significantly enhanced by means of plasma nitriding. Such materials are of interest for the use as bipolar plates of proton exchange membrane fuel cells (PEMFC). In this regard a new PTT method based on a strip hollow cathode (SHC-PTT) has been developed as a cost-effective process for surface modification of thin metal strips in continuous operation. A laboratory-scale SHC-PTT device operating in stationary treatment mode has been realized and short-time plasma nitriding of EN 1.4301 (AISI 304) austenitic stainless steel sheets has been studied. The obtained nitrided layers were investigated using GDOES and XRD. Further, the interfacial contact resistance of the sheets was measured and the corrosion behaviour was investigated by means of electrochemical methods. The obtained results clearly demonstrate the high potential of the new SHC-PTT method for further development in terms of treating thin steel strips in continuous operation.
It is shown that the use of nitrogen or carbon as alloying elements in plasma diffusion treatment... more It is shown that the use of nitrogen or carbon as alloying elements in plasma diffusion treatment of TiAl6V4 is beneficial for the load-supporting properties of the base material. The plasma diffusion treatment produces a compound layer consisting of nitrides or carbides and an inner diffusion zone, essentially characterized by the presence of nitrogen- or carbon-rich α-Ti crystals which are embedded in the metal matrix. This results in a hardness gradient from the interior to the surface. To avoid hydrogen embrittlement, plasma nitriding is performed in a pure nitrogen atmosphere. The formation of soot by carburizing could be avoided by optimizing the carbon flow during plasma carburizing. The influence of plasma nitriding and carburizing on the adhesion of the TiC coating depends on the plasma diffusion pretreatment and the conditions of the TiC coating. Plasma-nitrocarburizing pretreatment leads to the best adhesion of the TiC coating; the critical load of failure is 80% higher than in the case of TiC on base material. A critical load of approximately 33 N was found under the optimum parameters. We conclude that the combination of plasma diffusion treatment and TiC coating extends the tribological applicability of TiAl6V4 in many industrial sectors. Fretting fatigue and wear could be increased by a duplex plasma treatment combined with shot peening.
ABSTRACT Pulsed-DC plasma boriding in an Ar–BCl3 atmosphere was performed for pure titanium and t... more ABSTRACT Pulsed-DC plasma boriding in an Ar–BCl3 atmosphere was performed for pure titanium and the titanium alloy TiAl6V4 in the temperature range of 700–900°C. The plasma boriding leads to the formation of TiB2 and TiB at the surface for pure titanium as well as for TiAl6V4, depending on the process parameters. These phases were identified using X-ray diffraction (XRD). The amount of boron, oxygen and the alloying elements at the surface and the depth profiles were examined by glow-discharge optical emission spectroscopy (GDOS). The hardness profile was measured on metallographic sections after boriding. The high hardness of the layer is similar to the hardness known for titanium boride layers formed by plasma-assisted chemical vapor deposition (PACVD). Scratch tests indicate that the adhesion strength is relatively high, thus indicating a high potential for industrial applications under tribological conditions.
Sealless rolling bearings for use under media lubricated conditions are exposed to high tribocorr... more Sealless rolling bearings for use under media lubricated conditions are exposed to high tribocorrosive loads. To achieve the necessary wear resistance while keeping up the corrosion properties of the corrosion resistant steels low-temperature-plasma-diffusion-treatments were conducted. When scaling-up the developed low-temperature-plasma-nitriding-processes to industrial dimensions, it is necessary to reach the required surface conditions independently of the parts placement within the batch. Upscaling to industrial batch processes was analyzed by using the example of rolling bearings. To achieve a homogeneous treatment result, relevant factors like temperature distribution and component placement were taken into account. This allows to draw conclusions about the surface layer properties in dependence of temperature, batch arrangement and position within the batch to verify the treatment results homogeneity.
Forging tools are often showing short lifetimes compared to cold forming tools e.g. for sheet met... more Forging tools are often showing short lifetimes compared to cold forming tools e.g. for sheet metal forming. This is based on the process conditions where high local surface temperatures are alternating with chilling conditions due to the spray cooling with water based cooling lubricants. The resulting thermal shock is provoking fatigue of the tool material in the near surface regions. Crack initiation and crack growth due to thermal shock exposure then causes chipping of the tool steel material in the surface regions. These are starting points for extensive wear.Hardness and wear resistance of tool surfaces at elevated temperatures can be dramatically enhanced with nitriding pretreatments. This has become state-of-the-art for hot forming tool steels in many forging applications. With inappropriate adjustments of the nitriding parameters a decrease of the ductility can occur and will reduce the crack resistance of the tool surface especially under thermal shock conditions.The hot working steel DIN-1.2367 (X38CrMoV5) is currently one of the most often used chromium–molybdenum tool steels in the field of forging. Exemplary for this material is the influence of the nitriding parameters like temperature, nitrogen supply and plasma parameters on the nitriding depth, the maximum hardness and the crack sensitivity will be discussed.Nitrided samples will be investigated with methods developed for the adhesion measurement of hard coatings. It could be shown that this is also appropriate for a qualification of the crack sensitivity of tools. Comparative application tests in the production of automotive components show the influence on the wear behavior and lifetime of forging tools in an industrial environment.
Metal containing carbon films (a-C:H:Me) have very good tribological properties especially in red... more Metal containing carbon films (a-C:H:Me) have very good tribological properties especially in reducing the friction coefficient in addition to wear and adhesion reduction. Typical metals for this kind of coatings are tungsten, titanium or chrom. Beside these materials other metals, like zirconium, also offer a good option for reducing the friction coefficient or wear. The main problem of these films is that at temperatures higher than 300°C the usability is reduced because of degradation of the coatings due to graphitization and oxidation effects. The a-C:H:Zr-films were prepared by reactive d.c. magnetron sputtering in an argon/acetylene atmosphere with two zirconium targets. The tribological film properties were investigated by nanohardnes, pin on disk, wear and scratch tests. To identify the film characteristics at higher temperatures, samples were tempered at normal atmospheric pressure at 150°C to 550 °C for 1.5 hours. A polished 1.3343 steel was used as the substrate. The resu...
Die vorliegende Erfindung bezieht sich auf die Bereitstellung von Bauteilen fur Gaseinspritzsyste... more Die vorliegende Erfindung bezieht sich auf die Bereitstellung von Bauteilen fur Gaseinspritzsysteme und/oder Verbrennungsmotoren, welche eine geringe Storanfalligkeit und eine lange Standzeit aufweisen. Dazu werden die Bauteile, welche mit Flussig- oder Erdgas in Beruhrung kommen, zumindest an den Bereichen, welche mit Gas in Kontakt sind, beschichtet. Die Beschichtung zeichnet sich dabei durch eine hohe Verschleisfestigkeit, hohe Korrosionsfestigkeit, gunstige Reibungseigenschaften und eine gute AntI-Haftwirkung aus.
Duplex stainless steel is common in thick-walled components such as longitudinal welded pipes in ... more Duplex stainless steel is common in thick-walled components such as longitudinal welded pipes in the oil and gas industries and as parts of various machines in the chemical and food industries. Electron beam welding is a very suitable method for welding such components. Due to the high power density of the electron beam combined with the decreased evaporation temperature in a vacuum atmosphere, steel with a sheet thickness of up to 150 mm can be welded in one pass. In the case of the electron beam welding of duplex stainless steels, vacuum atmosphere in the working chamber causes a nitrogen effusion from the weld pool. The microstructure of the resulting weld is characterized by an unacceptable high ferrite content, which is the main reason for both low impact toughness and low pitting corrosion resistance. This work focuses on the influence of nitrided weld edge surfaces on metallurgical properties of the resulting welded joint. The aim here is to investigate the effect of increase...
ABSTRACT Beside its conventional applications such as improving the wear resistance of machine pa... more ABSTRACT Beside its conventional applications such as improving the wear resistance of machine parts and tools, plasma thermochemical treatment (PTT) can be successfully used as a method for surface modification to achieve specific surface properties. Surface electrical conductivity of austenitic stainless steel sheets, for example, can be significantly enhanced by means of plasma nitriding. Such materials are of interest for the use as bipolar plates of proton exchange membrane fuel cells (PEMFC). In this regard a new PTT method based on a strip hollow cathode (SHC-PTT) has been developed as a cost-effective process for surface modification of thin metal strips in continuous operation. A laboratory-scale SHC-PTT device operating in stationary treatment mode has been realized and short-time plasma nitriding of EN 1.4301 (AISI 304) austenitic stainless steel sheets has been studied. The obtained nitrided layers were investigated using GDOES and XRD. Further, the interfacial contact resistance of the sheets was measured and the corrosion behaviour was investigated by means of electrochemical methods. The obtained results clearly demonstrate the high potential of the new SHC-PTT method for further development in terms of treating thin steel strips in continuous operation.
It is shown that the use of nitrogen or carbon as alloying elements in plasma diffusion treatment... more It is shown that the use of nitrogen or carbon as alloying elements in plasma diffusion treatment of TiAl6V4 is beneficial for the load-supporting properties of the base material. The plasma diffusion treatment produces a compound layer consisting of nitrides or carbides and an inner diffusion zone, essentially characterized by the presence of nitrogen- or carbon-rich α-Ti crystals which are embedded in the metal matrix. This results in a hardness gradient from the interior to the surface. To avoid hydrogen embrittlement, plasma nitriding is performed in a pure nitrogen atmosphere. The formation of soot by carburizing could be avoided by optimizing the carbon flow during plasma carburizing. The influence of plasma nitriding and carburizing on the adhesion of the TiC coating depends on the plasma diffusion pretreatment and the conditions of the TiC coating. Plasma-nitrocarburizing pretreatment leads to the best adhesion of the TiC coating; the critical load of failure is 80% higher than in the case of TiC on base material. A critical load of approximately 33 N was found under the optimum parameters. We conclude that the combination of plasma diffusion treatment and TiC coating extends the tribological applicability of TiAl6V4 in many industrial sectors. Fretting fatigue and wear could be increased by a duplex plasma treatment combined with shot peening.
ABSTRACT Pulsed-DC plasma boriding in an Ar–BCl3 atmosphere was performed for pure titanium and t... more ABSTRACT Pulsed-DC plasma boriding in an Ar–BCl3 atmosphere was performed for pure titanium and the titanium alloy TiAl6V4 in the temperature range of 700–900°C. The plasma boriding leads to the formation of TiB2 and TiB at the surface for pure titanium as well as for TiAl6V4, depending on the process parameters. These phases were identified using X-ray diffraction (XRD). The amount of boron, oxygen and the alloying elements at the surface and the depth profiles were examined by glow-discharge optical emission spectroscopy (GDOS). The hardness profile was measured on metallographic sections after boriding. The high hardness of the layer is similar to the hardness known for titanium boride layers formed by plasma-assisted chemical vapor deposition (PACVD). Scratch tests indicate that the adhesion strength is relatively high, thus indicating a high potential for industrial applications under tribological conditions.
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Papers by Peter Kaestner