The development of corrosion- and wear-resistant high-performance coatings is important to improve components of mobile and stationary turbines, aerospace undercarriages, combustion engines, and hydraulic modules. New micro- and nanostructured coating materials and processes to machine these coatings are developed in order to increase the performance of workpieces and components, to enhance durability, and to reduce maintenance and manufacturing costs. At the Institute of Machining Technology (ISF), milling and grinding procedures have been developed for the preparation of the workpiece surface for the subsequent coating process. In contrast to conventional applications, the workpieces are not manufactured with the aim of achieving a minimized resulting surface roughness. Instead of this, a defined and adequate structure has to be generated, providing a good adhesion of the thermal sprayed coating on the workpiece surface. After first coating of the prepared substrates by a High-Velocity-Oxygen-Fuel (HVOF) coating process, the resulting surface topography does not have the required surface quality for a subsequent (Diamond Like Carbon) DLC coating process. In order to generate a more uniform surface structure, the deteriorated surface resulting from the HVOF coating process also has to be processed. Therefore, the application of an adapted grinding process with diamond wheels is used. 1. Introduction To increase the wear, erosion, and corrosion resistance of tribologically stressed functional surfaces, the use of thermally sprayed coatings increases. Typical applications for these slide or bearing surfaces are stationary turbines, aerospace undercarriages, combustion engines, and hydraulic modules [1]. One of these thermal spraying processes is the High-Velocity Oxygen Fuel (HVOF). Based on the high particle velocity a low porosity, high bond strength, and an increased hardness are the main advantages of this thermal spraying process [2, 3]. In order to obtain a good adhesion between the coating and the substrate, it is necessary to prepare the substrate surface. Although coinciding with several disadvantages, such as the necessity to clean the workpiece and the costs, a blasting process is usually used to activate the surface. In order to circumvent these disadvantages, other machining processes have to be considered. Obtaining unique surface structures which are similar to blasted surfaces regarding the roughness is also possible with other machining processes. These machining processes may be milling, grinding, or honing, for example. Depending on
References
[1]
T. N. Rhys-Jones, “Thermally sprayed coating systems for surface protection and clearance control applications in aero engines,” Surface and Coatings Technology, vol. 43-44, no. 1, pp. 402–415, 1990.
[2]
B. D. Sartwell and P. E. Bretz, “HVOF thermal spray coatings replace hard chrome,” Advanced Materials and Processes, vol. 156, no. 2, pp. 25–28, 1999.
[3]
R. Thorpe, H. Kopech, and N. Gagne, “HVOF thermal spray technology,” Advanced Materials and Processes, vol. 157, no. 4, pp. 27–29, 2000.
[4]
L. L. Boys, “Method for finishing thermal spray coatings,” in Proceedings of the Thermal Spray Coating Conference, pp. 135–138, Long Beach, Calif, USA, 1984.
[5]
R. B. Massad, “Diamond wheel grinding of thermal spray materials,” in Proceedings of the Thermal Spray Conference, pp. 139–146, 1984.
[6]
L. C. Casteletti, A. L. Neto, and G. E. Totten, “HVOF production of hard chromium substitution coatings for improved wear,” Industrial Heating, vol. 75, no. 1, pp. 53–57, 2008.
[7]
C. Rincón, G. Zambrano, A. Carvajal et al., “Tungsten carbide/diamond-like carbon multilayer coating on steel for tribological applications,” Surface and Coatings Technology, vol. 148, no. 2-3, pp. 277–283, 2001.
[8]
A. Khellouki, J. Rech, and H. Zahouani, “Influence of the belt-finishing process on the surface texture obtained by hard turning,” Proceedings of the Institution of Mechanical Engineers B, vol. 221, no. 7, pp. 1129–1137, 2007.
[9]
A. Khellouki, J. Rech, and H. Zahouani, “The effect of abrasive grain's wear and contact conditions on surface texture in belt finishing,” Wear, vol. 263, no. 1–26, pp. 81–87, 2007.
[10]
M. Omar, “Finishb？nder-Technologie und Einsatzm？glichkeiten,” in Honen in Forschung und industrieller Anwendung, Qualit？t in der Fertigung, Fachtagung, Vulkan, 1995.
[11]
K. U. Paffrath, T. Heymann, and D. Biermann, “Umweltfreundlicher Glanz,” WB Werkstatt und Betrieb, vol. 143, pp. 62–64, 2010.
[12]
D. M. Schibisch, “Kühles Band für beste Güte,” Automobil Industrie, vol. 44, no. 10, pp. 84–88, 1999.
[13]
G. Rudloff, “Der superfinish-prozess—superfinish-bearbeitung mit band,” Moderne Schleiftechnologie und Feinstbearbeitung, pp. 10-1–1019, 2004.
[14]
G. Rudloff, Superfinish von Automobil-Komponenten Mit Band, Spanende Fertigung Prozesse, Innovationen, Werkstoffe, Vulkan, Essen, Germany, 5th edition.
[15]
W. Tillmann, M. Tolan, P. Hollingsworth, L. Baumann, and M. Paulus, “Nanostructured WC-Co coatings manufactured by fine powders (-10 + 2？μm) with ultra-fine carbides (400？nm) by means of HVOF,” in Proceedings of the International Thermal Spray Conference & Exposition, Hamburg, Germany, 2011.
[16]
J. K. N. Murthy, D. S. Rao, and B. Venkataraman, “Effect of grinding on the erosion behaviour of a WC-Co-Cr coating deposited by HVOF and detonation gun spray processes,” Wear, vol. 249, no. 7, pp. 592–600, 2001.
[17]
B. Zhang, X. Liu, C. A. Brown, and T. S. Bergstrom, “Microgrinding of nanostructured material coatings,” CIRP Annals—Manufacturing Technology, vol. 51, no. 1, pp. 251–254, 2002.
[18]
Z. H. Deng, B. Zhang, and F. Cheng, “Investigations of grinding forces for nanostructured WC/12Co coatings,” Key Engineering Materials, vol. 304-305, pp. 151–155, 2006.
[19]
K. Bonny, P. De Baets, J. Quintelier et al., “Surface finishing: Impact on tribological characteristics of WC-Co hardmetals,” Tribology International, vol. 43, no. 1-2, pp. 40–54, 2010.
[20]
J. Jiang and R. D. Arnell, “The effect of substrate surface roughness on the wear of DLC coatings,” Wear, vol. 239, no. 1, pp. 1–9, 2000.
[21]
Z. Zhong, “Machining of thermally sprayed WC-Co coatings,” Materials and Manufacturing Processes, vol. 16, no. 1, pp. 103–112, 2001.
[22]
F. Klocke and W. K？nig, Fertigungsverfahren 2. Schleifen, Honen, L？ppen, Springer, Berlin, Germany, 4th edition, 2005.
