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Pawlus P.,Rzeszow University of Technology | Michalczewski R.,Institute for Sustainable Technology | Lenart A.,Aerojet Rocketdyne | Dzierwa A.,Rzeszow University of Technology
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology | Year: 2014

This paper describes the tribological effect of surface topography on friction and wear under dry fretting regime of a point contact. Experiments were made using SRV4 ball-on-disc tribotester. 100Cr6 sphere of 64 HRC (Rockwell method, scale C) hardness co-acted with a disc made of 42CrMo4 steel with hardness of 40 HRC. Fretting tests were carried out under dry gross slip conditions. The diameter of ball was 10mm. During tests, normal load was kept constant at P = 50N within the contact. Duration of each test was 15min. Tests were performed in 26 temperature in the chamber at 39-43% of relative humidity. Displacement amplitude was 0.1mm (stroke was 0.2mm) with frequency of 20Hz. The disc samples had different textures obtained after one process (grinding, vapor blasting, or polishing) and two process (grinding or vapor blasting followed by lapping). During tests, the friction force was monitored as a function of time. Wear of disks and balls was measured after the test using white light interferometer. Surface roughness height of discs, determined by the Sq parameter was in the range: 0.01-4.5μm. It was found that initial surface roughness height had a significant influence on friction and wear in dry gross slip conditions. For rougher disc surfaces, the friction force in initial test stage and wear of co-acting parts were higher. © IMechE 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Wiecinski P.,Warsaw University of Technology | Smolik J.,Institute for Sustainable Technology | Garbacz H.,Warsaw University of Technology | Kurzydlowski K.J.,Warsaw University of Technology
Vacuum | Year: 2014

The aim of the present work was to investigate erosion properties of the nanostructured Cr/CrN multilayer coatings on titanium Ti6Al4V alloy. Seven types of multilayer (Cr/CrN)×8 coatings were deposited by PVD vacuum arc method. The coatings had the same total thickness and number of the constituent layers but differed in the thickness ratio of Cr and CrN constituent layers (QCr/CrN parameter). The erosion test was performed using sandblasting equipment. Small (40-80 μm), spherical silica particles were used as an erodent, which hit the surface at angle of 90°. The SEM and STEM observation were focused on the cracking behaviour as well as on the microstructure changes in the substrate material and ductile Cr layers. The investigations demonstrate that the applied surface treatment significantly improves the erosion resistance of the titanium alloy. The best erosion resistance was achieved for the Cr/CrN with the thickness ratio of 0.81. Increase, as well as decrease of the QCr/CrN parameter resulted in decrease of erosion properties. Observations performed on cross-sections through the erosion zones revealed the small cracks, which were observed mainly in the CrN layers. The STEM observations showed also microstructure changes in the Cr layers and refinement of grain size in substrate material due to the accommodation of plastic deformation. Microscopic examination revealed also the mechanisms of the effective cracks blocking at the interfaces between the layers as well as in the microstructure of the ductile Cr layers. © 2014 Elsevier Ltd. All rights reserved.

Wiecinski P.,Warsaw University of Technology | Smolik J.,Institute for Sustainable Technology | Garbacz H.,Warsaw University of Technology | Kurzydlowski K.J.,Warsaw University of Technology
Thin Solid Films | Year: 2011

Five different nanostructured, multilayer coatings (CrN/Cr)x8 with different thickness ratio of Cr and CrN layers were deposited by PAPVD (Plasma Assisted Physical Vapour Deposition) vacuum arc method on Ti6Al4V titanium alloy. The microstructure, chemical and phase composition of the CrN and Cr sub-layers were characterized by SEM with EDX and Cs-corrected dedicated STEM on cross-sections prepared by focus ion beam. Besides, hardness and Young's modulus of the (Cr/CrN)x8 coatings has been measured. The adhesion has been tested by scratch test method. The obtained (CrN/Cr) multilayer coatings, 5-6 μm in thickness, have homogeneous and nanocrystalline structure, free of pores and cracks. The microstructures of Cr and CrN layers consist of columnar grains below 100 nm in diameter. The hardness and Young's modulus of these coatings depend linearly on thickness ratio of Cr and CrN layers. The decrease of the thickness ratio Cr/CrN 0.81 to 0.15 results in the increase of hardness from 1275 HV to 1710 HV and Young's modulus from 260 GPa to 271 GPa. © 2011 Elsevier B.V. All rights reserved.

Smolik J.,Institute for Sustainable Technology
Central European Journal of Engineering | Year: 2011

This article presents results which enabled the determination of the role of CrN coating and the influence of its thickness on the effectiveness of hybrid layer "nitrided layer / CrN coating" in the process of increasing the durability of forging dies. Dies coated with hybrid layers "nitrided layer / CrN coating" with various CrN coating thickness were - after different maintenance periods - subjected to metallographic testing, 3D shape testing and SEM analysis. Hardness distribution was also determined. The obtained results revealed that for all tested dies, independently from CrN coating thickness, the main mechanisms of their destruction was mechanical and thermal fatigue, and plastic deformation. It has been shown that the main role of CrN coating in the hybrid layer "nitrided layer / PVD coating" is to counteract a high temperature influence the source of which is forging on die material. In order to do so the CrN coating should be characterized by a considerably lower thermal conductivity coefficient to steel and low hardness so that it can efficiently resist fatigue processes in the forging process. Based on testing conducted by means of the sin2ψ method, it was revealed that internal stresses are vitally important for CrN coating for fatigue resistance of hybrid layer "nitrided layer / CrN coating" during the forging process. © Versita Sp. z o.o.

Wiecinski P.,Warsaw University of Technology | Smolik J.,Institute for Sustainable Technology | Garbacz H.,Warsaw University of Technology | Kurzydlowski K.J.,Warsaw University of Technology
Solid State Phenomena | Year: 2015

The aim of this work was to investigate the thermal stability and corrosion resistance of the Cr/CrN multilayer coatings. For this purpose, multilayer Cr/CrN coating was deposited on Ti6Al4V titanium alloy using the PVD vacuum arc method. The Cr/CrN coating had a thickness of 5.6 µm and was composed of 16 layers (8 Cr and 8 CrN). The Cr layers had a thickness of 0.26 µm and were composed of columnar grains. The CrN layer had a thickness of 0.32 µm and was characterized by a needle-like structure. Because of the potential application of the investigated coatings, thermal stability in the temperature range of 300-500°C as well as corrosion behaviour during salt fog tests was analysed. The investigation showed that the microstructure of Cr/CrN multilayer coating was stable up to 400°C. At this temperature, only a slight increase in the thickness of the transition Cr2N layer was observed. Annealing at a temperature of 500°C changed the microstructure of the constituent Cr and CrN layers and caused a decrease in their thicknesses due to an increase in the thickness of the Cr2N transition layer. Annealing at 500°C also increased the hardness of the Cr/CrN coating. XPS analysis revealed the presence of the CrO3 and Cr2O3 on the surface after annealing. Cr/CrN multilayer coatings also exhibit excellent corrosion resistance in salt fog test. No corrosion product was observed on the Cr/CrN coating surface after 120 hours of test. © (2015) Trans Tech Publications, Switzerland.

Ratajski J.,Koszalin University of Technology | Olik R.,Koszalin University of Technology | Suszko T.,Koszalin University of Technology | Dobrodziej J.,Institute for Sustainable Technology | Michalski J.,Institute of Precision Mechanics
Sensors | Year: 2010

The article presents a complex system of design, in situ visualization and control of the commonly used surface treatment process: the gas nitriding process. In the computer design conception, analytical mathematical models and artificial intelligence methods were used. As a result, possibilities were obtained of the poly-optimization and poly-parametric simulations of the course of the process combined with a visualization of the value changes of the process parameters in the function of time, as well as possibilities to predict the properties of nitrided layers. For in situ visualization of the growth of the nitrided layer, computer procedures were developed which make use of the results of the correlations of direct and differential voltage and time runs of the process result sensor (magnetic sensor), with the proper layer growth stage. Computer procedures make it possible to combine, in the duration of the process, the registered voltage and time runs with the models of the process. © 2010 by the authors.

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