Werkzeug-Einlaufverhalten beim Microfinishen

Die Untersuchungen vergleichen das Einlaufverhalten metallisch gebundener Diamant-Microfinishwerkzeuge in unterschiedlichen Konditionierzuständen. Die Analyse erfolgt werkstück-, prozess- als auch werkzeugseitig anhand von Oberflächengüte, Prozesskräften und Werkzeugtopographie. Hierdurch wird die Wirkung der Konditionierzustände auf das Einlaufverhalten des Werkzeugs respektive das Erreichen der stationären Prozessphase untersucht und hinsichtlich der auftretenden Wechselwirkungen analysiert.The present investigations compare the run-in behavior of metal-bonded diamond microfinishing tools in different conditioning states. The analysis is carried out on the workpiece, process and tool sides on the basis of surface quality, process forces and tool topography. The effect of the conditioning states on the run-in behavior of the tool and the achievement of the stationary process phase is investigated and analyzed with regard to interactions

The effect of machined surface conditioning on the coating interface of high velocity oxygen fuel (HVOF) sprayed coating

Roughening the substrate surface is essential for thermal sprayed coatings. In this regard, sandblasting has established itself as an easy to use surface conditioning procedure. The quality of the obtained roughness depends on the conditions of the sandblasting material, adjusted parameters, and the kind of the process execution (manual or mechanical). These preconditions limit the reproducibility of the roughness obtained. Sandblasting causes residual compressive stress and may also lead to the inclusion of sand particles and notches in the roughened surface, which affects the interfacial properties of the coating, as well as the flexural strength of the coated parts. The hardness of the roughened surface plays, thereby, an important role. However, in order to reliably avoid these effects, microfinishing can be used as an alternative to generate a homogenous roughened substrate surface, control the induced residual stresses, and increase the reproducibility. In addition, the roughened surface pattern can be produced during the chip forming process of the to-be-coated parts. The utilization of the appropriate combination of machining processes and parameters should lead to the required surface pattern and thus to an enhanced coating adhesion and flexural strength of the coated part. The induced residual stresses and the quality of the obtained surface roughness have a significant influence on the coating adhesion and the lifespan of the coated parts. This paper aims to analyze, as a first step, the effect of the turning and microfinishing on the surface conditioning of the bearing steel 100Cr6 (AISI 52100). The investigation concludes by comparing the microfinished with the sandblasted surfaces with regard to the interface to and the adhesion of the WC–Co high velocity oxygen fuel (HVOF) sprayed coatings on them. Surface conditioning plays a decisive role by the induced residual stresses and the elimination of adhesion defects

Innovative X-ray diffraction and micromagnetic approaches for reliable residual stress assessment in deep rolled and microfinished AISI 4140 components

The residual stress state in the subsurface is a key element of surface integrity. It is well known to have a significant impact on a component's properties in terms of fatigue behavior and resistance to wear and corrosion. For this reason, adjusting residual stresses during manufacturing is a major challenge in modern production engineering, to improve and ensure a component's fatigue strength. In this context, hydrostatic deep rolling of the workpiece surface using adapted parameters enables the targeted induction of compressive residual stresses into subsurface layers. Due to specific properties regarding subsurface and topography for functional components in tribological applications, a further machining operation by microfinishing following deep rolling seems to be purposeful. In particular with regard to the production of components exposed to periodic load changes when used, the process combination can enable a substitution of the typically required conventional subsurface zone hardening. With the aim of economical process design, the corresponding parts can be manufactured with significantly reduced time and costs. Efficient and well-founded methods for monitoring the resulting influence on the subsurface zone properties are essential for a reproducible and target-oriented process design. The prevailing method for the non-destructive assessment of residual stresses in both academia and industry is X-ray diffractometry using the sin2 ψ-method. However, this method is time-intensive and requires complex instrumentation. Thus, efforts have been undertaken in past decades to develop alternative methods for the efficient and reliable characterization of residual stresses. In this research, the applicability of the cos α-method in X-ray diffractometry and a micromagnetic approach for residual stress assessment was investigated, analyzing deep rolled and microfinished AISI 4140 specimen conditions. In addition to the diffractometric and micromagnetic measurements, metallographic and topographic analyses of machined surfaces were carried out. Deep rolling was found to induce significant compressive residual stresses of up to −1100 MPa. After microfinishing of the deep rolled surfaces, favorable compressive residual stresses remain in the subsurface, reaching approximately up to −750 MPa. Based on this, the production of tailored surfaces with respect to a suitable combination of topography and subsurface is possible. For all surface states investigated, a good agreement between the two approaches in X-ray diffraction was found. Magnetic Barkhausen noise (MBN) measurements prove to be well applicable for an efficient and holistic assessment of surface integrity in the subsurface of deep rolled and microfinished AISI 4140 specimens

Structuring Surfaces by Microfinishing Using Defined Abrasive Belts

Microfinishing, also known as superfinishing or short-stroke honing, is a commonly used process for generating technical surfaces focusing on tribological applications. Due to microfinishing processes high surface qualities are manufacturable regarding the surface roughness and bearing area ratio. While the required characteristics for tribological loaded workpieces are changing with their rising significance, the surface structuring is becoming more and more important. With the use of defined abrasive belts, the possibilities of surface structuring by microfinishing are enhanced. The possibilities and challenges concerning surface structuring by microfinishing applying defined abrasive belts are described in this research study. Therefore, a geometrical-kinematic simulation is used to predict the theoretical structures generated by microfinishing, while in experimental investigations the influences of kinematic parameters and a multi-stage process sequence are considered

The impact of additive manufacturing on the mechanical properties of a stainless precipitation hardening steel

A stainless precipitation hardening steel has been qualified for powder bed fusion of metals using a laser beam. The mechanical and microstructural properties of additively manufactured samples have been thoroughly investigated and compared to samples of the very same material made by means of ingot casting. Additive manufacturing is feasible and can deliver superior mechanical properties. Additionally, the surface quality will be improved by means of wet abrasive jet machining, and its impact on the residual stresses has been shown

The impact of additive manufacturing on the mechanical properties of a stainless precipitation hardening steel

Finanziert aus dem Open-Access-Publikationsfonds der Universität Siegen für ZeitschriftenartikelA stainless precipitation hardening steel has been qualified for powder bed fusion of metals using a laser beam. The mechanical and microstructural properties of additively manufactured samples have been thoroughly investigated and compared to samples of the very same material made by means of ingot casting. Additive manufacturing is feasible and can deliver superior mechanical properties. Additionally, the surface quality will be improved by means of wet abrasive jet machining, and its impact on the residual stresses has been shown