Hans-Werner Zoch

Hans-Werner Zoch
Institut für Werkstofftechnik Bremen (IWT) · Director

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Publications

Publications (419)
Article
Kurzfassungen Das Härten von Bauteilen ist im Allgemeinen einer der letzten Fertigungsschritte eines mehr oder weniger langen Herstellungsprozesses. Fehler, die beim Härten infolge unzureichender oder falscher Abschreckbedingungen entstehen, können zum Verlust der Teile führen oder eine Nachbehandlung erforderlich machen und verursachen dementsprec...
Article
Full-text available
Unvermeidbarer Verzug, der in nicht umwandelnden Werkstoffen durch thermische Spannungen während der Abschreckung entsteht, hängt von relativ wenigen Parametern ab: Härtetemperatur, Umgebungstemperatur, Wärmekapazität, Wärmeleitfähigkeit, Dichte, thermische Dehnung, E-Modul, Poisson-Zahl, Streckgrenze und Verfestigungsverhalten. Zusätzlich beeinflu...
Article
Abstract In the current work the distortion behavior of a complex automotive component was investigated. It turned out that the part geometry was the dominant influencing factor. Furthermore it was discussed what makes the part geometry an important carrier of distortion potential. Finally it was investigated on barlike samples how distortion can b...
Article
Nitrogen as an alloying element can improve the corrosion resistance and the mechanical properties of stainless steels. Therefore, nitrogen-alloyed martensitic stainless steels, such as X30CrMoN15-1, have been developed in recent decades and conventional processing of this steel by casting or powder metallurgy is well understood. However, only very...
Article
Additive manufacturing in the powder bed by means of laser powder bed fusion (L-PBF) combines the fast production of metallic components with complex geometrical structures with a high degree of customization and low raw material consumption. However, there is a high demand for the development of new alloys to achieve the desired properties of addi...
Article
Carbonitriding serves to improve the properties of steel components. The carbon and nitrogen content and the microstructure comprising martensite, retained austenite, and finely distributed nitrides and carbides are significant parameters determining the properties of a component. Our present knowledge posits that these multi-phase microstructures...
Article
In the field of massive forged components the mechanical engineering industry searches for processes with increasing energy and resource efficiency. The new generation bainitic steels are promising for such application because of the high strength, toughness and fatigue properties. In order to achieve the desired mechanical properties, the developm...
Article
Carbonitriding is used to improve the properties of steel components. The carbon and nitrogen content and the microstructure comprising martensite, retained austenite, and finely distributed nitrides and carbides are significant parameters determining component properties. Current state of the art posits that these multi-phase microstructures deter...
Article
In many applications in the roller bearing industry, bainitic microstructures are considered superior to martensitic [1–3] due to their specific advantages such as compressive residual stresses at the surface of a though hardened steel component and the increased toughness for hypereutectoid steels. Especially tolerance to damage incurred in operat...
Article
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Rotary swaging is an incremental cold forming process that changes beneath the geometry also the microstructure and mechanical properties of the workpiece. Especially a new process design with Eccentric Flat Shaped Dies (EFSD) influences both the kind and amount of stress and plastic strain and consequently the material structure, and hence the mat...
Article
Nitriding is a widely used treatment to increase the performance of unalloyed and alloyed steels. Because nitriding majorly affects the hardness of the surface region of the material it is common to perform a quenching and tempering treatment before nitriding in order to get a suitable core hardness and microstructure for application. The hardness...
Article
Material properties like yield stress and hardness change during forming. Metastable austenitic steels are characterized by an elevated work hardening potential due to strain-induced transformation of austenite into martensite especially by multi-stage processing. An application of a new rotary swaging process design with Eccentric Flat Shaped Dies...
Article
Full-text available
Carburising followed by martensitic hardening is state of the art in the gear industry today. Carburisation followed by isothermal transformation into a partial or fully bainitic microstructure has not been systematically examined and evaluated yet. Especially isothermal transformation of carburised parts into lower bainite is promising in terms of...
Article
During forging the tools have to resist high thermal and mechanical loads. Therefore, forging dies are usually nitrided in order to increase the wear resistance of the surface areas. Compared to nitriding carbonitriding increases the hardness depths in shorter treatment times. Due to the (carbo-)nitriding, the surface near region gets a better hot...
Article
Carbonitriding serves to increase the strength and wear properties of steel components. The carbon and nitrogen concentration and the depth distribution decisively determine the resulting properties. Optimal profiles create an ideal microstructure of martensite, residual austenite, finely distributed nitrides, carbonitrides and inherent compressive...
Chapter
Caused by different factors, the interest in extended fatigue life of components is increasing. Therefore, the demand for additional knowledge about the fatigue behaviour in the VHCF regime grows. In the case of high strength steels, fatigue tests mostly reveal that multiple failure mechanisms occur. However, the common statistical analysis of cons...
Article
Full-text available
The beneficial strength properties of bainitic microstructures have been perceived since several years. The transformation kinetics and different morphologies of bainite were analyzed scientifically in depth and with increasing understanding the application of bainite is focus now. But still, bainitic microstructures are mainly utilized with chemic...
Article
Kurzfassung Um den hohen Beanspruchungen bei der Warmmassivumformung zu begegnen, werden die Randbereiche der eingesetzten Werkzeuge nitriert. In vorangegangenen Untersuchungen zu nitrierten Gesenken zeigte sich, dass die Verschleißtiefe an kritischen Stellen deutlich über der Nitrierhärtetiefe lag. Eine Steigerung der Nitrierhärtetiefe ist durch N...
Conference Paper
Carbonitriding is mainly used to enhance the hardenability and wear resistance of unalloyed steels. Last year investigations have shown that improved component properties can efficiently be obtained by carbonitriding also low alloy and even higher alloy steels. The importance of carbonitriding rises. In the past carbonitriding was done with constan...
Article
Some high manganese austenitic steels show extraordinarily high ductility due to twinning induced plasticity (TWIP). The TWIP-effect is based on the formation of crystal twins in the austenitic lattice structure as a response to mechanical strain resulting in an extraordinary high ductility. Therefore, TWIP steels are very interesting for forming p...
Article
Kurzfassung Das Niederdruck-Aufkohlen bietet dem Anwender ein Verfahren, mit dem unter geringem Einsatz von Kohlenwasserstoffen quasi randoxidationsfreie, metallisch blanke Oberflächen erzeugt werden [1]. Die bei diesem Verfahren entstandene randoxidationsfreie Randschicht lässt gegenüber einer durch Randoxidation geschädigten Oberfläche höhere Dau...
Article
Low pressure carburizing offers the ability to produce bright-metallic surfaces without unwanted internal oxidation known from carburizing at atmospheric pressure but with lower consumption of hydrocarbon [1]. The expected increase in fatigue life of low pressure carburized parts compared to gas-carburized parts could not be achieved due to other s...
Article
Full-text available
Kurzfassung Eigenspannungen spielen bei der Bewertung der Güte von Bauteilen eine große Rolle. Der Aufwand für die Messungen der Eigenspannungen, insbesondere von Eigenspannungstiefenverläufen, ist aber oft sehr groß. So müssen z. B. bei röntgenografischen Methoden sukzessive oberflächennahe Schichten aufwendig abgetragen werden. Bei Tiefen größer...
Article
In the foregoing years, micro components were frequently employed in various sectors such as the electronics and medical industry. In order to produce these components in large amounts and satisfying quality, the production processes have to be improved constantly. Heat treatment represents a critical step in the production chain of micro component...
Article
Kurzfassung Hoch belastete Bauteile wie Zahnräder werden zumeist einsatzgehärtet, um die spezifische Beanspruchbarkeit an der Zahnflanke und im Zahnfuß einzustellen. Der Wärmebehandlungsprozess umfasst hier Aufkohlen, gefolgt von Abschrecken auf RT in gasförmigen oder flüssigen Medien. Das Ergebnis der Wärmebehandlung ist in den meisten Fällen ein...
Article
en The economic and ecological need for reduced weight of automobiles leads to increasing activities in recent years. One way to achieve this aim is to use modified designs for components with a high weight. Here the gear box and especially the gears have a potential for significant weight reduction. But besides the functional behavior of the compo...
Article
In this study, the methods of Water Jet Peening (WJP) and Laser Shock Peening (LSP) were compared to Shot Peening (SP) and investigated in terms of induced residual stresses (RS), microstructure, surface topography and fatigue properties for a case-hardened steel. Different modifications of the surface topography were observed for the different pee...
Article
Chromium nitride (CrNx) films are frequently used as interlayers to enhance the adhesion of hydrogenated amorphous carbon (a-C:H) films on steel substrates. The microstructure of these CrNx interlayers has a direct influence on the corrosion protection properties of the a-C:H films. A dense and defect-free microstructure can improve the corrosion r...
Article
Kurzfassung Metal-Dusting ist eine spezielle Form der Hochtemperaturkorrosion, die unter aufkohlenden Bedingungen in der Petrochemie, in thermochemischen Wärmebehandlungsprozessen und teilweise auch in Gas- und Ölbrennern anzutreffen ist. In Laborversuchen in einem elektrisch beheizten Quarzglas-Rohrreaktor sowie in einem Feldversuch an einem indus...
Article
Kurzfassung Durch Nitrieren kann die Beanspruchbarkeit von Zahnrädern, insbesondere die Flanken- und Zahnfußtragfähigkeit, signifikant gesteigert werden. Die Dauerfestigkeit und damit die Lebensdauer nitrierter Bauteile steigen mit zunehmender Nitriertiefe, wobei die benötigte Nitriertiefe abhängig von der Größe der Verzahnung ist. In der Praxis wi...
Article
In this study, the distortion of steel shafts was investigated before and after induction hardening. Several essential influencing factors in the manufacturing process chain regarding cold drawing, cutting method, notches on the shafts, and induction hardening were analyzed by design of experiment (DoE). Further necessary examinations of microstruc...
Conference Paper
Plasmanitriding is a thermochemical surface heat treatment of steel components to produce nitride layers which increase wear-, corrosion- and fatigue resistance. Research into plasmanitriding lately showed that there is a significant and characteristic amount of ammonia formed off the process gases nitrogen and hydrogen. This research paper is aime...
Article
Rotary swaging is an incremental cold forming process and allows for the cost effective manufacture of cylindrical light weight components such as rods or hollow shafts. The process has a widespread use particularly in the automotive industry for example for the manufacture of axles and steering spindles. Besides the generation of desired geometrie...
Article
Today case hardening of highly stressed gear wheels is state of the art, to meet the specific load demands at flank and tooth root. The heat treatment is including a carburization and quenching step in liquids or in gaseous media. The result of the heat treatment of gear wheels is strongly impacting the strength and the load capacity at flank and f...
Article
In order to improve the rolling contact fatigue (RCF) behavior of gear steels, a concept to increase their damage tolerance is developed alternatively to the conventional approach of improving the degree of steel cleanliness. For that purpose, Cu is used as a main alloying element in order to trigger the precipitation of nano-sized Cu precipitates...
Article
Modern lightweight construction containing hybrid materials and structures allow the improvement of a wide range of density specific properties. In this regard, the great potential of structures consisting of carbon fibre reinforced plastics (CFRP) and aluminium (Al) is far from being exhausted. In order to exploit this potential, novel joint conce...
Conference Paper
The gear wheel manufacture is one of the key technologies for power train systems and in automotive industry. These high performance parts require stable processes and narrow tolerances in order to sustain the load over a long service life. However manufacturing related distortion, which causes shape and size alteration, requires larger cutting and...
Article
Die Dauerfestigkeiten carbonitrierter Biegeproben aus den Stählen 18CrNiMo7-6 und 20MnCr5 wurden untersucht. Es wurden jeweils 4 Varianten hergestellt, die sich in der Wärme- und der Oberflächenbehandlung unterscheiden: Neben der konventionellen Gasaufkohlung wurden carbonitrierte Proben mit einem niedrigen und einem erhöhten Randstickstoffgehalt v...
Article
Full-text available
The extensive use of lubricant during rotary swaging is particularly required for a good surface finish of the work piece and the reduction of tool wear. Abandonment of lubricant would improve the ecological process-balance and could also accelerate for further work piece refinements. Also cleaning of the manufactured components becomes obsolete. T...
Article
The average operation temperature of rolling element bearings in standard applications is rising. Due to this advancing demand, the chemical composition of martensitic bearing steels like 100Cr6 (DIN 1.3505; SAE 52100) and 100CrMnSi6-4 (DIN 1.3520) has to be adapted. To enhance the tempering resistance of these steels several alloying approaches co...
Article
Rotary swaging is an incremental bulk metal forming process for the manufacture of cylindrical light weight components. Nowadays, rotary swaging is carried out under the extensive use of lubricant to avoid abrasive and adhesive tool wear and to provide the desired work piece quality. This work presents rotary swaging tools exhibiting hard coated an...
Article
Rundkneten ist ein Massivumformverfahren zur Herstellung von Leichtbaukomponenten aus zylindrischen Halbzeugen. Es setzt derzeit einen intensiven Einsatz von Schmiermitteln voraus, um Werkzeugverschleiß zu minimieren und die gewünschte Bauteilqualität bereitzustellen. In dieser Arbeit werden strukturierte und hartstoffbeschichtete Rundknetwerkzeuge...
Article
Kurzfassung Eine Prozesskette für die Herstellung von Maschinenbauteilen besteht im Allgemeinen aus mehreren Prozessschritten, wie z. B. Stranggießen, Warmwalzen, Glühen, Richten, Drahtziehen, Richten und Polieren, spanende Bearbeitung, Induktionshärten und Schleifen. Verzug wird häufig nach der finalen Wärmebehandlung beobachtet. Verantwortlich da...
Article
In modern lightweight structures different requirements for components occur. In many cases they cannot be fulfilled by a single material in an optimum way. Therefore, the use of different materials with different properties is desirable. The combination of CFRP (carbon fibre reinforced plastics) and aluminium alloys is promising for structural com...
Article
Kobasko et al.have primarily shown that rapid water quenching can create compressive residual stresses near the surface and thereby a significant increase in the fatigue-limit (Intensive Quenching). Such processes result in an increase in hardness. Depending on steel grade, dimensions of the component and quenching intensity through hardening or on...
Article
Kurzfassung Durch Umformen von Stahl bei niedrigen Temperaturen lassen sich formgenaue Werkstücke ressourcenschonend und wirtschaftlich herstellen. Besonders wenn Bauteile auf einem konstant hohen Qualitätsniveau in großen Stückzahlen benötigt werden, wie beispielsweise im Automobilbau, bieten Kaltmassivumformprozesse häufig die optimale Lösung. We...
Article
Kurzfassung Das Laserstrahlbeschichten wird als Reparaturverfahren von Bauteilen und zur Auftragung von Funktionsschichten eingesetzt. Über die Ermüdungseigenschaften laserstrahlbeschichteter Bauteile existieren jedoch nur wenige Untersuchungen. Aus diesem Grund wird in dieser Veröffentlichung das Ermüdungsverhalten von Vierpunktbiegeproben aus dem...
Chapter
Die Oxidation der Metalle ist dadurch gekennzeichnet, dass im Laufe derselben an der Oberfläche der Metallphase eine Schicht des festen Reaktionsproduktes gebildet wird. Diese Reaktionen, die bei hohen Temperaturen dickschichtige Oxidationsprodukte bilden, bezeichnet man als Verzunderung. Da die Mechanismen der Hochtemperaturkorrosion sehr komplizi...
Chapter
In Faserverbundwerkstoffen (FVW) übernehmen die Komponenten Fasern und Kunststoffmatrix jeweils spezifische Funktionen. Die Fasern (F) gewährleisten die Zugfestigkeit und Steifigkeit in der Faserrichtung; häufig wird dabei auch die Anisotropie der mechanischen Eigenschaften der Fasern ausgenutzt. Der Matrix (M) kommen drei Aufgaben zu: sie gewährle...
Chapter
Bei der Fertigung duromerer Faserverbundwerkstoffe (FVW) entsteht gleichzeitig mit dem Verbundwerkstoff das spätere Bauteil. Eine gute Prozesskontrolle, basierend auf den Kenntnissen erreichter Prozessgrößen und Prozessbedingungen sowie deren Reproduzierbarkeit, sind daher von großer Relevanz. Materialografische Untersuchungen unter Verwendung mikr...
Chapter
Die mechanischen Eigenschaften von Faserverbundwerkstoffen (FVW) werden im starken Maße von der Faser‐Matrix‐Interaktion bestimmt, da die Kraftübertragung im Werkstoff von Faser zu Faser über die Matrix geschieht. Eine gute Faser‐Matrix‐Haftung ist daher entscheidend für die mechanische Leistungsfähigkeit. Durch die Applizierung eines „Haftvermittl...
Chapter
Die heute als Electron backscatter diffraction (EBSD) bezeichnete Analysetechnik geht zurück auf die Entdeckung der sog. Kikuchi‐Linien, die bereits 1928 von Nishikawa und Kikuchi im Transmissionselektronenmikroskop beobachtet wurden. Noch im selben Jahr beschrieben sie, dass solche Beugungslinien auch im Reflexionsmodus erfasst werden können – die...
Chapter
Die bei Veränderungen der Temperatur durch Wärmeausdehnung oder durch Phasenumwandlung auftretenden Längenänderungen eines Werkstoffes lassen sich mit Hilfe eines Dilatometers messen.
Article
Die AiF-Leitinitiative „EcoForge“ hat erfolgreich Möglichkeiten entwickelt, die Prozesskette zur Herstellung von Schmiedebauteilen einschneidend zu verkürzen. Wesentlicher Bestandteil des Vorhabens war die Integration des Wärmebehandlungs- beziehungsweise Quenchprozesses in die Bauteilfertigung der Schmiedelinie, um so definierte homogene Gefügezus...
Article
Full-text available
In the project “EcoForge: Resource-efficient process chains for high performance parts” a new efficient forging process chain is developed, which allows a saving in energy of more than 30 %. This process chain will be optimized for high-strength ductile bainitic steel (HDB). The forging heat is directly utilized to substitute reheating process step...
Article
Full-text available
Unlike thermoset fiber reinforced plastics (FRPs), thermoplastic FRPs provide excellent workability under elevated forming temperatures. Thus, complex shaped components made of thermoplastic FRPs become increasingly important for advanced lightweight applications, such as multi-material automotive bodies in white. To enable transition bonding betwe...
Article
High strength aluminium alloys with improved stability at elevated temperatures for micro components, which are needed e.g. in the automotive or the micro electronics industry, require new alloys and advanced production processes regarding primary shaping, heat treatment and cold forming. Their development is part of the Collaborative Research Cent...
Article
This chapter will first present the basic mechanisms of distortion generation. Then the systematic of unavoidable dimensional and shape changes will be discussed. For the handling of avoidable distortion, the concept of distortion potential and the corresponding carriers will be introduced. Based on this, the method 'Distortion Engineering' and the...
Article
The fatigue life of the bearing steel 52100 (100Cr6) in bainite and martensite conditions was investigated up to 2 × 109 cycles. The tests were performed under cycling tension (R = 0.1) and tension–compression (R = −1) on a piezo-electric ultrasonic testing equipment. The specimens are designed with a cylindrical part in the highly stressed centre....
Article
In this investigation notched and fracture mechanics specimens were machined from the steel SAE 5120 (DIN EN 20MnCr5) in two cleanliness conditions. The first material is used for high-performance components and is nearly free of oxides. The second material is standard steel and used for common requests in the field of drive engineering containing...
Article
In this contribution very high cycle fatigue properties of the martensitic stainless 18% chromium steel X90CrMoV18 (DIN 1.4112, AISI Type 440B) in air and biofuel with 85% ethanol are presented. They were gained on notched specimens which were loaded at a stress ratio of R = 0.1 under differing load frequencies. In all cases, fatigue failure occurr...
Conference Paper
Die AiF-Leitinitiative "EcoForge" hat zum Ziel die Prozesskette zur Herstellung von Schmiedebauteilen effizient zu verkürzen. Wesentlicher Bestandteil des Vorhabens ist die Integration des Wärmebehandlungs- bzw. Quenchprozesses in die Bauteilfertigung der Schmiedelinie, um so definierte Gefügezustände in Bauteilen direkt aus der Schmiedewärme einst...
Article
Nitriding and nitroarburizing is a thermochemical heat treatment with increasing demand in more and more various applications. Many of them need cleaning and activation of the surface. Depending on pre processing conditions and steel grade it can be rather difficult, to get a homogeneous clean and activated surface for the nitrogen and carbon diffu...
Article
Full-text available
Components in hybrid design become more and more important in terms of their lightweight potential. In this context the demand for weight saving in aerospace structures leads to increasing numbers of applications of fiber reinforced plastics (FRP) for structural components. Besides FRP, metallic components are still parts of the primary structures....
Conference Paper
Abstract – The method of force-indentation tests provides the necessary requirements for a rapid measurement of hardened surface layers e.g. after case hardening, not only to obtain information about a hardness value and a correlated tensile strength according to DIN EN ISO 18265. Furthermore, the determination of the elastic-plastic deformation is...
Article
Kurzfassung Das weit verbreitete geregelte Gasaufkohlen hat den Nachteil, dass aus regelungstechnischen Gründen mit sauerstoffhaltigen Aufkohlungsatmosphären gearbeitet werden muss, was zwangsläufig zu einer Bauteilrandschichtschädigung in der Form von Randoxidation führt. Um Schädigungen durch Oxidation und Manganeffusion zu unterdrücken und auch...
Article
Tools for hot massive forming are exposed to complex loads. The abrasive wear of the thermally, mechanically and tribologically most loaded part of the engraving is the main cause of failure. In order to resist the high loads, the surfaces and boundary areas of the tools are nitrided. As an alternative to gaseous nitriding the tools are also treate...
Article
The continuous miniaturization of products needed e.g. in the automotive or the microelectronics sector requires process chains, which allow the manufacturing of microscopically small components in high quantities. The development of the required processes and technologies is the aim of the Collaborative Research Centre 747 “Micro Cold Forming” of...
Chapter
The plastic behavior of metals depends strongly on microstructural features such as dislocations, grain boundaries or precipitations. Some of these microstructural features show size effects depending not only on the size of the feature, but also on the size of the specimen.
Article
Abstract Manufacturing of microstructured mold surfaces was realized by the micromachining of thick sol–gel silica hybrid coatings. The films were deposited onto pre-machined steel molds by spin coating using NaOH-catalyzed sols from organosilicate precursors. The effect of the sol synthesis and the heat treatment on the mechanical and chemical pro...
Article
Kurzfassung Um den hohen Beanspruchungen bei der Warmmassivumformung zu begegnen, werden die Oberflächen und Randbereiche der eingesetzten Werkzeuge nitriert. Neben dem Gasnitrieren werden die Werkzeuge alternativ durch Salzbadnitrocarburieren behandelt. Das Plasmanitrieren wird nur zum geringeren Teil angewendet. Dabei bietet die Behandlung im Pla...
Article
Kurzfassung Bisherige Forschungsergebnisse weisen darauf hin, dass durch Stickstoff stabilisierter Restaustenit eine positive Wirkung auf die Dauerfestigkeit hat, insbesondere bei Anteilen von Hertz'scher Pressung im Belastungskollektiv. Das Carbonitrieren wird deshalb in der industriellen Praxis heute wieder häufiger angewandt bzw. gefordert. Die...
Article
Micro cold forming processes sometime require thin sheets of high strength materials often with a thickness below 30 μm to manufacture products with good mechanical properties. Due to its high strength and anti-recrystallization properties, aluminum-scandium is a promising material for such processes, but cannot be rolled down to the specified thic...
Article
Full-text available
In many cases different requirements for structural components exist, which cannot be fulfilled by a single material in an optimal way. Under such conditions, the use of different materials with suitable properties may be of avail. With regard to lightweight design CFRP (carbon fibre reinforced plastics) and aluminium alloys are a promising combina...
Article
Due to the special mechanical properties of carbonitrided surfaces containing martensite and nitrogen stabilized austenite, carbonitriding is of increasing interest to industry. he interaction of carbon and nitrogen in the reactive atmosphere calls for tedious pre-trials, if deined nitrogen and carbon depth proiles are required. However, the result...
Article
In order to resist the high loads in hot massive forming, the surfaces and boundary areas of the used tools are nitrided. Alternatively to gaseous nitriding the tools are also treated by salt bath nitrocarburizing. Plasma nitriding is only rarely used. But the plasma treatment has some advantages over gaseous nitriding. For example partial treatmen...