Veinthal R.,Tallinn University of Technology |
Sergejev F.,Tallinn University of Technology |
Zikin A.,Tallinn University of Technology |
Zikin A.,ACT Research GmbH |
And 2 more authors.
Wear | Year: 2013
The conventional Fe-Cr-C overlay is studied due to the lack of information regarding the response of this material system to impact wear conditions. Previously the same material system has been successfully used in erosion wear conditions. The high stress abrasive impact wear resistance and low and high surface fatigue wear behaviour of a Fe-Cr-C overlay (FeCrC-matrix) produced by plasma transferred arc welding (PTA) were studied.The overlays with varied PTA hardfacing process cooling parameters were tested. The cooling parameters were as follows: (1) active cooling-application of gas cooling of substrate during the welding process; (2) passive cooling-application of copper plate under substrate with constant temperature of 20. °C and (3) standard-cooling in the air. Different cooling time leads to differences in microstructure and formation of residual stresses (surface cracks, etc.).The abrasive impact testing reveals the difference in the overlays response to the cyclic stressing at high impact energy. The surface fatigue wear (SFW) testing is accompanied by the abrasive impact wear (AIW) testing. The SFW incorporates cyclic loading of the overlays surface with spherical indenter with radius of 10. mm at high loads, while in AIW testing the specimens are bombarded almost in normal direction with granite gravel particles (diameter of <6. mm) with the energy in the range of 0.14-0.52. J.The study proposes the relation between high energy impact/abrasive wear behaviour and the surface fatigue wear behaviour of Fe-Cr-C hardfacings produced under varying cooling conditions. © 2013 Elsevier B.V.
Felkel Y.,ACT Research GmbH |
Dorr N.,ACT Research GmbH |
Glatz F.,University of Applied Sciences Wiener Neustadt |
Varmuza K.,Vienna University of Technology
Chemometrics and Intelligent Laboratory Systems | Year: 2010
The most common analyses carried out to assess gas engine oil quality include determination of viscosity, total base number (TBN), and total acid number (TAN). TAN has been considered to be an important indicator of oil quality, specifically in terms of defining oxidation and the extent of acidic contamination of used oils. TAN can be determined by potentiometric titration, and typical values for used oils can reach up to 4 mg KOH/g. A more convenient approach for the determination of TAN is based on infrared (IR) spectral data and multivariate regression models. We developed partial least-squares (PLS) models for the determination of TAN using IR data measured from monograde mineral gas engine oils (SAE 40, medium ash) that have been used in sewer and wood gas engines run with gaseous fuels from a sewage plant and a wood gasification plant, respectively. The final model performance was 0.07 mg KOH/g for the standard error of prediction (SEP). Essential for the development of powerful empirical models was an appropriate variable selection by combining expert knowledge, biPLS or dyn-biPLS, and a genetic algorithm. The optimum complexities of the models (the number of PLS components) and their prediction performances have been estimated by repeated double cross validation (rdCV). © 2009 Elsevier B.V. All rights reserved.
Linz M.,ACT Research GmbH |
Linz M.,Saarland University |
Winkelmann H.,ACT Research GmbH |
Hradil K.,Vienna University of Technology |
And 2 more authors.
Engineering Failure Analysis | Year: 2013
Stresses in the near-surface area can form cracks which join together, propagate and combine, forming pits due to material spall-off. The stresses causing the cracks are not only influenced by external forces, residual stresses stored in the material also play an important role. Moreover, these residual stresses can vary during the lifetime of the sliding components. Cracks are found in the wear tracks of linear oscillating ball contacts on AISI 4140 steel. The crack propagation at the surface is longitudinal to the sliding direction. Residual stress analysis by X-ray diffraction (XRD) shows that normalized samples develop tensile stresses in the near-surface zone of the wear track. Residual stresses are found to be higher transversal to the moving direction than longitudinal. © 2013.
Scheichl B.,Vienna University of Technology |
Scheichl B.,ACT Research GmbH
AIP Conference Proceedings | Year: 2013
A novel self-consistent description of time-mean two-dimensional turbulent-boundary-layer flow separating from a bluff body at arbitrarily large globally formed Reynolds numbers is presented. Contrasting with previous approaches, the theory deals with a sufficient delay of flow detachment or, correspondingly, increase of the turbulence intensity so as to both settle the question of the actual position of separation and trigger a turbulent boundary layer exhibiting a large relative streamwise velocity deficit. At separation, a generic variation of the velocity profile close to the body surface with the third power of the distance from it is detected. The Euler stage resulting from the breakdown of the incident boundary layer and governed by its vorticity is envisaged in detail. Specifically, an analytical solution to the central linear vortex-flow problem could be established. This represents the essential ingredient for the understanding of the multi-layered substructure of the flow more close to the surface, which completes the picture of gross separation at the Euler scale. Most important, the analysis does not resort to any specific turbulence closure. Concerning the canonical situation of circular-cylinder flow, a first comparison between the predicted and publicly available experimentally obtained values of the separation angle is encouraging. © 2013 AIP Publishing LLC.
Gabler C.,ACT Research GmbH |
Gabler C.,Vienna University of Technology |
Dorr N.,ACT Research GmbH |
Allmaier G.,Vienna University of Technology
Tribology International | Year: 2014
The effect of varying the cationic structural moiety of bis(trifluoromethylsulfonyl)imide based ionic liquids (ILs) on the constitution of the tribolayer was studied by a X-ray photoelectron spectroscopic (XPS) approach. Tribolayers generated from five different ILs were characterised by means of XPS imaging of the top-most surface layers and by performing depth profiling. Differences in the concentration of tribochemical reaction products such as fluorides, detected on the topmost layers indicate that between the selected ILs an order of decreasing decomposition takes place phosphonium>imidazolium>pyrrolidinium>sulfonium>ammonium. Similar results could be shown in the depth profiles of the tribolayers. Hence, the influence of the cationic moiety cannot be neglected. © 2014 Elsevier Ltd.
Curkovic L.,University of Zagreb |
Curkovic H.O.,University of Zagreb |
Salopek S.,ACT Research GmbH |
Renjo M.M.,University of Zagreb |
Segota S.,Ruder Boskovic Institute
Corrosion Science | Year: 2013
Nanostructured TiO2 thin films were deposited on AISI 304 austenitic stainless steel by sol-gel process, dip coating technique. Influence of the number of layers, addition of polyethylene glycol (PEG) in initial sol, morphology and the surface roughness parameters of titania films on corrosion resistance of coated stainless steel were examined. Prepared films were characterized by SEM-EDS and AFM analysis. Electrochemical corrosion behavior of the coated stainless steel substrates was evaluated in simulated marine environment in 3wt.% aqueous NaCl solution by electrochemical impedance spectroscopy (EIS) and in 0.5M aqueous HCl solution by potentiodynamic polarization. © 2013 Elsevier Ltd.
Katsich C.,ACT Research GmbH |
Badisch E.,ACT Research GmbH
Surface and Coatings Technology | Year: 2011
Within this work, the effect of carbide degradation in a WC/W2C reinforced Ni-based hardfacing was assessed under abrasive and combined impact/abrasive conditions. In view of the above, a WC/W2C reinforced Ni-based hardfacing was deposited by plasma transferred arc (PTA) welding using different welding currents. Microstructure was characterised by quantitative metallography to determine specific structural parameters: mean carbide diameter and carbide area fraction. Scanning electron microscopy (SEM, EDS) and X-ray diffraction (XRD) were also used to characterise carbide dissolution mechanism. Tribological behaviour was determined with a 3-body abrasion test according to ASTM G65 and with a cyclic impact/abrasion test (CIAT). Results showed significant carbide degradation with increasing welding current, resulting in a significant reduced primary carbide content and carbide diameter. Reduced carbide content indicated a significantly wear rate increase under pure 3-body abrasion conditions. Specific wear energy was determined under pure abrasive condition and showed significant dependence on the primary carbide content. However, wear rates under combined impact/abrasion were at constant level due to the reduction of the brittle primary carbide content. © 2011 Elsevier B.V.
Ilo S.,ACT Research GmbH |
Tomala A.,ACT Research GmbH |
Badisch E.,ACT Research GmbH
Tribology International | Year: 2011
A tools lifetime absolutely depends on the material properties and lubrication. By a lubricant absence, the direct contact between the materials might cause an increase of friction and wear, which might lead to a tools failure. That is why wear prediction and control are important requirements in industry. The wear prediction experiments in this study were performed for an unlubricated (dry) bushing/shaft system of relatively high load and low sliding speed. Two different commercially available tool steels were used for tribological investigations. Normal load and temperature were considered as independent variable in the wear testing. The results showed that the extensive oxidation of metals have a positive factor on wear. When the temperature raises formation of the protective oxide layers consequently change the wear transition to the mild oxidative wear. Based on the classical wear equations and on the chemical oxidation kinetics concepts a wear prediction model was developed and statistically evaluated in the case when metallic contact wear as the predominant wear mechanism was combined with the oxidation of metals. © 2011 Elsevier Ltd. All rights reserved.
Ilo S.,ACT Research GmbH |
Just C.,ACT Research GmbH |
Xhiku F.,ACT Research GmbH
Materials and Design | Year: 2012
Hard-particle metal matrix composites (MMC) represent an efficient way of increasing the lifetime of machinery equipment which is exposed to severe wear conditions. The abrasive wear resistance of these materials, usually designed by reinforcement with tungsten carbides, is highly dependent on the MMC's microstructure. Plasma transferred arc (PTA) is a commonly used and efficient welding method for hardfacing deposition. Dissolution of carbide markedly influences the microstructure parameters, decreasing the carbide volume fraction as well as the mean carbide diameter, whereas matrix hardness increases with increasing carbide dissolution. However, optimisation of the multiple, process determining quality characteristics is a key factor for successful application in industrial practice. In this paper, the grey relational Taguchi method was used for the optimisation of PTA-processing in hardfacing of WC/W2C-reinforced Ni-based MMC, considering multiple quality characteristics of the microstructure parameters relevant to abrasion resistance. An L8 orthogonal array with three control factors (welding current, welding speed and oscillating speed) was used to study linear effects and interactions on signal-to-noise ratios of the various quality responses (carbide volume fraction, equivalent diameter, matrix hardness). Based on this study, optimised processing conditions of the hard-particle MMC fabrication were defined. © 2011 Elsevier Ltd.
Rojacz H.,ACT Research GmbH |
Hutterer M.,ACT Research GmbH |
Winkelmann H.,ACT Research GmbH
Materials Science and Engineering A | Year: 2013
To exploit the full potential of materials used at elevated temperatures, it is crucial to understand their deformation and fracture mechanisms. High Temperature Single Impact Studies were performed to evaluate deformation mechanisms at different energy and momentum levels and their correlation to temperature. The limitations of materials regarding their impact resistance, the resulting deformation and fracture mechanisms were investigated. NiCrBSi based Metal Matrix Composites (MMC), reinforced with TiC-NiMo or Cr3C2-Ni particles, manufactured by Plasma Transferred Arc Cladding along with two different types of steels were tested and compared to study different types of deformation and fractures. Results indicate more ductile deformation behaviour of the investigated steels, while the MMCs show brittle behaviour at several temperatures. Critical impact loadings were determined at elevated temperatures to limit the range of use in impact dominated high temperature environment. Results show that the influence of different momenta at constant impact energy levels cannot be neglected. © 2012 Elsevier B.V.