ICMCTF2008 Session G6-2: Surface Pre-Treatment, Coating Post-Treatment and Treatment Process Integration

Monday, April 28, 2008 1:30 PM in Room Sunset

Monday Afternoon

Start	Invited?	Item
1:30 PM	Invited	G6-2-1 Influence of Plasma Nitriding and Surface Roughness on the Wear and Corrosion Resistance of Thin Films (PVD/PECVD) J. Ellermeier, C. Berger, O. Durst (Institut für Werkstoffkunde, TU Darmstadt, Germany) Influence of plasma nitriding and surface roughness on the wear and corrosion resistance of thin films (PVD/PECVD) The aim of the applied research was to determine the wear and corrosion resistance of PVD multilayer coatings with ZrC and PECVD DLC coatings in dependence of different machining methods for the substrate surfaces. As substrate material 42CrMo4 was chosen. 42CrMo4 is a relativ cheap material with a certain amount of impurities in the microstructure. The substrate surfaces were prepared with different roughness to investigate the influence of different machining methods to the adhesive force and lastly to the wear and corrosion resistance of the coatings. For the corrosion resistance it is important that there are as few defects in the coating as possible. Otherwise pitting corrosion will appear. Finally the roughness of the substrate has an important influence to the amount of holes in the coatings. In a further step the substrates were plasma nitrided to reach a higher hardness of the substrate. There was the question whether the higher hardness is able to improve the wear resistance through an supporting effect to the coating and whether the emplacement of nitrogen in the microstructure improves the corrosion resistance in the case of defects in the coating.
2:10 PM		G6-2-3 Surface Characterization and Phase Transformation Behavior of the Magnetron Sputtering Nickel-Phosphorus-Based Coatings F.B. Wu (National United University, Taiwan) Magnetron sputtering technique was employed to fabricate the Ni-P binary and multicomponent alloy coatings with amorphous or nanocrystallized structures. The results from surface morphology investigation and X-ray diffraction phase identification revealed that significant nanocrystallization for the Ni-P alloy coatings occurred due to higher manufacture temperatures in sputtering processes. The wavy surface characteristic with a degraded roughness of tens nm in Ra was attributed by the crystallization phenomenon and energetic particle impingement caused by substrate heating and plasma environment, respectively. Post annealing from 350 to 550°C was conducted to evaluate the precipitation behavior and to elucidate the surface morphology evolution of the Ni-P alloy coatings. The effect of alloying elements, including Al and Cu, in Ni-P coatings on crystallization and surface homogeneity were evaluated. In addition, the crystallization behavior and precipitation phenomenon of the Ni-P-based coatings manufactured by various techniques were intensively discussed.
2:30 PM		G6-2-4 Fast Regime - Fluidized Bed Machining (FR-FBM) of Atmospheric Plasma Spraying (APS) TiO₂ coatings M. Barletta, S. Guarino (Università di Roma Tor Vergata, Italy); G. Bolelli, L. Lusvarghi (University of Modena and Reggio Emilia, Italy); G. Rubino (Università di Roma Tor Vergata, Italy); A. Boschetto, A. Gisario (La Sapienza Università di Roma, Italy) This paper deals with the development and application of a new technique, Fast Regime - Fluidized Bed Machining (FR-FBM), for easy-to-automate finishing of as-deposited Atmospheric Plasma Spraying (APS) TiO₂ coatings on AISI 1040 steel substrates. The effects of leading FBM operational parameters, namely, abrasive size, jet pressure and processing time, were evaluated by using a two-level full factorial design of experiments. Machinability of APS TiO₂ coatings were found to be highly dependent on jet pressure and on abrasive grain size as they affect the contact conditions between the abrasive and machined surface as well as the finishing force. In addition, the control of processing time was found to be of crucial importance, governing the interaction time between the abrasive and machined surface. By modifying these conditions, FR-FBM decreases roughness parameters of as-deposited APS TiO₂ coatings up to 3-4 times and imparts minimal defects or alterations to the machined surface, while it is always able to guarantee the form accuracy and the respect of the closest geometrical tolerances.
2:50 PM		G6-2-7 Improving the Substrate Adhesion of PVD Coatings by Anode Layer Source Treatment W. Waldhauser (Joanneum Research Forschungsgesellschaft mbH, Austria); W. Heinz (Austrian Academy of Sciences, Austria); J.M. Lackner, M. Kahn, E. Brandstaetter (Joanneum Research Forschungsgesellschaft mbH, Austria) The quality of PVD coatings is determined by its adhesion to the substrate. State-of-the-art techniques for substrate pre-treatment for adhesion improvement are glow discharges. However, this method cannot be applied for temperature sensitive and electrically non conductive substrates. In contrast to glow discharges, ion sources produce a plasma and accelerate ions with electrostatic or electromagnetic forces. In the scientific field, mainly gridded ion sources are applied, which have a high degree of complexity and require substantial maintenance to operate due to the limited lifetime of grids and the electron source. Thus, they are scarcely applicable for industrial processes. As an alternative, gridless ion sources offer an elegant solution to ion beam production. One type of gridless ion source is the so-called anode layer source (ALS) which was used in this work for pre-treatment of different types of steel prior PVD coating at room temperature. The effect of the plasma treatment was investigated by contact angle measurements and microscopic investigations of the substrate surfaces. The adhesion of sputtered TiN coatings was measured by scratch test, the residual stress of the coatings was determined by XRD. The highest increase of the film adhesion was observed for hard substrates. Best results were found for medium ion energies of approximately 1000 eV. The most significant effects are occurring during the first 5 minutes of pre-treatment. The increase of the film adhesion correlates with a decrease of the residual stresses in the films. High ion energies cause a change of the surface topography of the substrate and lead to reduced film adhesion.