Search Results for der

Knowledge of the production, the properties and the relevant regulations for industrial gases are a prerequisite for the smooth application of thermal spraying in manufacturing and research. This is why corresponding supply concepts for this coating technology were developed. These have proven extremely successful in their practical application and they ensure the user the necessary gas purity at any time. The following article serves to inform the readers about the underlying principles of gas technology and to clearly show that, in the respective specialist gas industry, they have the right partner for solving their coating problems. Paper text in German.

This paper reviews the results of thermal spraying on the magnesium alloy AZ 91. By plasma, arc and HVOF spraying various metal based alloys were used as coating materials. The layers were investigated with regard to microstructure, bonding and corrosion resistance. Paper text in German.

In this investigation, the concepts of fracture mechanics are put to use to determine the adhesion strength of WC-Co coatings on metal substrates. The paper explains how test samples are produced and describes the procedures used to obtain fracture mechanics data. Adhesion strength is determined based on local energy release rates (crack closure integral method) and is verified using a finite element model of the test sample. With this approach, the spraying parameters for WC-Co can be more precisely tuned than would be possible with a frontal pull test. Paper text in German.

This paper reviews the new DIN EN ISO personnel qualification and quality management standards and EWF training guidelines for European thermal sprayers. EWF education and training programs run for a period of three weeks, filling critical gaps in knowledge and experience. The primary aim of the ISO standards is to facilitate a reproducible process for spraying coatings of a consistent quality. Paper text in German.

Diamond films have been deposited on WC - 6% Co hard metal tools by the DC plasma jet CVD synthesis. The parameters of the process (gas composition, temperature of the gas phase and the substrate, process pressure) as well as of the substrate surface (material, pretreatment) are related to the diamond film growth. For machining abrasive materials the hard and wear resistant diamond coatings must adhere good to the substrate. The wear behaviour of thin diamond films on hard metals under cavitation treatment has been examined. Thus the conditions of diamond synthesis have been varied especially concerning the coating duration and the process pressure and engineering. The cavitation test reacts more sensitive to coating defects of pm size than the conventional testing methods (scratch test, indenter method) and considers the microstructure of the material. Paper text in German.

Aluminium alloys are extensively used materials which can be found in all kinds of industrial applications. They have distinctive advantages such as a high strength/weight ratio, an excellent workability and a good corrosion behaviour. However, aluminium alloys have wear resistance properties which limitate further use of these alloys. Plasma transferred arc surfacing (PTA) using the DCCP-technology (Direct Current Combined Polarity) was used for enhancing wear properties of different aluminium alloys (AlMgSi0.5, AlSi12) by the formation of an alloyed layer with added ceramics. Hardness of the base material could be increased by more than two times while the wear resistance of the modified aluminium alloy was about ten times higher compared to the base material. Paper text in German.

The demand for better paper qualities and for higher speed of the paper web requires a constant technological development of the existing calendering process. An important factor in modern calendering is the heated metal roll. Its surface has an important influence on the gloss and the smoothness of the paper. During operation these rolls are heated to temperatures of up to 200°C. Additionally, the rolls are exposed to severe abrasive wear by fine hard filler materials and to corrosion by the moisture of the paper. The SUMECAL coating systems - especially developed for calender rolls - surpass the hard chromium platings by far regarding the scratch and wear resistance and demonstrate better calendering properties. Paper text in German.

This paper presents research highlights obtained over the past three years in the course of a DFG-funded project on new and emerging diagnostic methods for thermal coating. It describes the tools and techniques used, the particle and substrate variables monitored, the accuracy of each measurement, and various associations with coating properties. Paper text in German.

The aim of this work is to determine how to control the microstructure and tribological properties of HVOF-sprayed TiC composite coatings. The powders used in the study were made by the SHS process and contained a mixture of TiC and either FeCr20Ni10 or FeCr18Ni15Mo3, which serve as a binder and give the sprayed coatings additional corrosion resistance. The composites produced were assessed based on metallographic examination and wear testing. The results show how the structure of the SHS powder changes due to the injection molding process and how the tribological properties of the HVOF layers are influenced by spraying conditions and the formation of mixed carbides. Paper text in German.

This paper provides a sampling of current and emerging applications for thermal spraying both in manufacturing and in equipment repair. As the examples show, thermal spraying is making an impact in many areas of industry, including automotive, aviation, biomedical, energy, printing, pulp and paper, and textiles, as well as in military and defense. Paper text in German.

This paper discusses some of the recent improvements in plasma powder surface build-up welding technology and provides examples of its use in different areas of industry. It describes the coating properties achievable with newly developed filler alloys and how they compare with conventional hardcoats. It also discusses the growing use of manual overlay PTA welding among small and midsize companies and the factors behind it. Paper text in German.

Arc spraying is an economical method for applying metallic layers due to its high spray rates and uniform melting of spray particles. The main disadvantage is the difficulty in achieving sufficient particle velocity to ensure good layer adhesion. This study investigates the influence of nozzle geometry, arc power, and gas pressure on the size and velocity of particles in an arc spray jet. The experiments were conducted using particle image velocimetry (PIV) to measure the spatial and velocity distribution of particles in flight. For X45Cr13 steel, particle velocities were found to be between 85 and 95 m/s at a gas volume flow of around 1 m 3 /min. Velocities of up to 150 m/s were ultimately achieved, but at the expense of higher atomizer gas consumption. Paper text in German.

This paper investigates the influence of nozzle design on the quality of Al 2 O 3 coatings produced by atmospheric plasma spraying. It compares the thermal and deposition efficiency of different plasma guns along with the porosity and adhesion strength of the resulting coatings. The intent of the study is the application of convergent-divergent nozzles as an economic alternative to the nozzles typically used for atmospheric plasma spraying. Paper text in German.

This study assesses the potential use of thermally sprayed dicalcium diiron pentaoxide (Ca 2 Fe 2 O 5 ) for thermoelectric generators. Ca 2 Fe 2 O 5 coatings up to 2 mm thick were produced by atmospheric plasma spraying and examined. Compared to the bulk material, the coatings exhibit lower thermal and electrical conductivity. The Seebeck coefficient could not be measured, and the thermoelectric performance was inadequate. The limitations derive not only from the thermal spray process, but also the material itself.

Much of the research being done in arc wire spraying deals with new nozzle geometries and secondary atomizing gas flows. This study, instead, focuses on pulsed current power. Spray trials are conducted using a conventional electric arc gun and an inverter that produces large current pulses with controlled amplitude and frequency. Droplet formation and detachment are monitored with a high-speed camera that records shadow images synchronized with current and voltage measurements. The images are processed into analog signals that are converted to the frequency domain and the Fourier coefficients are plotted, providing a relative measure of the influence of pulse frequency on droplet ablation. The results suggest that arc spraying can be improved using pulsed current power and that gas pressure and pulse time have greater influence than pulse frequency.

In order to homogenize the properties of APS sprayed coatings, the spray process was investigated using numerical simulations combined with innovative diagnostic techniques. The process was subdivided into three areas: the plasma torch, the free jet, and coating formation. By simulating these areas separately and combining the results, appropriate process parameters for homogenized coatings were obtained. For a comprehensive computation of coating formation which, besides the impact, flattening, and solidification of particles, includes the mechanical properties of the coating, a volume of fluid algorithm is coupled with a finite element model. In order to verify the modeling of the plasma jet and to provide input data for the coating formation, diagnostic efforts were concentrated on measuring the gas temperature of the plasma as well as particle shape, velocity, and temperature. The results of spatially resolved 3D analysis employing an innovative tomography system are presented and compared with the numerical results.

Tungsten coatings on copper substrates were produced and subjected to thermal shock loads in an electron beam device. The aim was to minimize the erosion rates thus caused. They are basically dependent on the level and type of porosity. Moreover, material erosion can also be directly influenced by the spraying parameters in coatings with the same relative density. In this connection, the chamber pressure, powder size and spraying distance play a decisive role.

Traditionally, large moulds for manufacturing of CFRP (carbon fiber reinforced plastics) parts are machined from a solid metal block making this way of manufacturing very energy and time consuming. Using wire arc spraying thin-walled moulds can be produced by spraying onto an original mould and separating the coating. In order to create a reliable and high quality product the manufacturing process needs to be highly reproducible. Thus the spraying process requires monitoring and control, which can be done using artificial neural networks (ANN). In our approach, for monitoring the process the diagnostic system PFI (Particle Flux Imaging) is used to characterize the spray particle stream, which is essentially achieved by fitting an ellipse to an image of the particle stream. Comparing deviations from a reference ellipse recorded for an “optimal” coating process provides data that can subsequently be used for process control. Investigations performed by the method of design of experiments (DOE) show a very strong correlation of the parameters pressure, current, and voltage with certain parts of the PFI data: for example the semi-minor axis of the ellipse depends linearly on voltage and current but quadratic on pressure. These results can further on be used to control the coating process by ANN. This paper discusses the application of this method and its feasibility for industrial use.

The main goal of this work is to improve the coating properties of three-cathode atmospheric plasma sprayed coatings with respect to porosity and residual stresses. This was done by use of numerical simulation coupled with advanced diagnostic methods. A numerical model for the triple injection of alumina feedstock, as well as acceleration and heating of the powder particles in the characteristic threefold symmetrical plasma jet cross section produced by a three-cathode-plasma torch was developed. The modeling results for the standard injector’s position “0” were calculated and experimentally verified by Laser Doppler Anemometry (LDA). Based on the criteria defined for concentrated feedstock transport and homogeneous thermal treatment of powder particles in the plasma jet, the optimal injection position was found. In the next step a previously developed, coupled CFD-FEM-simulation model was used for simulations of the coating build-up, describing flattening, solidification and deformation due to shrinkage for alumina particles on a rough substrate surface.

One approach for controlling the twin wire arc spray (TWAS) process is to use optical properties of the particle beam like length or brightness of the beam as input parameters for a process control. The idea is that changes in the process like eroded contact nozzles or variations of current, voltage and/or atomizing gas pressure can be detected through observation of optical properties of the particle beam. It can be assumed that if these properties deviate significantly from those obtained from a beam recorded for an optimal coating process the spray particle and so the coating properties change significantly. Thus, the goal is to detect these optical deviations and compensate occurring errors by adjusting appropriate process parameters for the wire arc spray unit. One cost effective method for monitoring optical properties of the particle beam is to apply the process diagnostic system PFI (Particle Flux Imaging): PFI fits an ellipse to an image of a particle beam thereby defining easy to analyze characteristic parameters by relating optical beam properties to ellipse parameters. Using artificial neural networks (ANN) mathematical relations between ellipse and process parameters can be defined. Thus in the case of a process disturbance through the use of an ANN-based control new process parameters can be computed to compensate particle beam deviations. In this paper, it will be shown that different process parameters can lead to particle beams with the same PFI parameters.