Papers

ICMCTF2006 Session A2: Surface Engineering for Very Harsh Thermo-Chemical Environments

Thursday, May 4, 2006 1:30 PM in Room Sunrise

Thursday Afternoon

Start	Invited?	Item
1:30 PM		A2-1 Fouling and Coking at High Temperatures on Metal Surfaces G. Dickakian (Fouling and Coking Technology, Inc.) When processing hydrocarbon feedstock's in refinery and petrochemical plants, deposition of organic and/or inorganic materials on hot metal surfaces can lead to a number of severe operational problems such as heat transfer. The mechanism of fouling and coking on hot metal surfaces has been investigated for a number of years. The chemical composition, incompatibility, contamination and equipment metallurgy are key causes of the problems. Over a period of thirty years, we have developed a test method using equipment for measuring fouling and coking on hot metal surfaces. This method consists of a tube-in-shell heat exchanger which can be heated up to 1100 deg.F at 1000 psig pressure. These heat exchangers are available in a number of metallurgies including C/S, S/S 314, S/S 316, S/S 445, aluminum and metal coated heat exchangers which have been coated by a high temperature vaporization process. Results of a number of investigations will be presented. These include sulfur related furnace tube fouling, jet fuel oxidation and delayed coking furnace tubes.
2:10 PM		A2-5 An Innovative Thin Film for Surface Protection from Fouling Deposits on Turbine Engine Components D. Dye, B.K. Gupta, W. Stowell (General Electric Aviation) A thin film coating for low temperature protection of surface degradation deposits on turbine engine components has been developed. This thin oxide acts as a barrier for deposition on critical surfaces that has been shown to result in degradation of engine performance. The coating system consists an oxide layer of a high temperature metallic system, and an overcoat layer of noble metal group to provide additional surface protection. Testing of the coating system has shown significant reductions in carbonaseous, or "coke", deposits on the walls of engine hardware wetted by hydrocarbon fluids and operating at elevated temperatures. Compressor efficiency gains are also realized with the coating by minimizing foulant buildup and maintaining smooth surface finishes on airfoils.
2:30 PM		A2-6 Structural and Tribological Investigation of Sol-Gel Al₂O₃ -CeO₂ /Silica Nanocomposites on Mg Alloys R. Phani, S. Santucci (University of L’Aquila, Italy) The physical,chemical and mechanical properties of aluminum alloys make them attractive materials for automotive and aerospace applications. However, these materials are susceptible to corrosion and wear. This work discusses the potential of using sol-gel based coatings consisting of SiO₂Al₂O₃ and 15wt.% of CeO₂. The CeO₂ component provides enhanced corrosion protection, while SiO₂ and Al₂O₃ impart corrosion as well as wear, abrasion and scratch resistance properties. Thin films of SiO₂ containing nanocomposites of Al₂O₃,CeO₂(15wt% of each)as corrosion inhibitors were deposited on aluminium substrates by dip coating technique. The deposited films were subjected to sintered at 180°C/10h.Structural and compositional properties of the films have been investigated by employing scanning electron microscopy (SEM)and energy dispersive X-ray. The presence of Si,Al,Ce and O has been confirmed in the deposited films. UV absorption measurements as well as stretching mode vibrations of the films were observed by Fourier transform infrared spectroscopy. X-ray diffraction measurements showed amorphous nature of the annealed films. Adhesion strength failure measurements on films performed by scratch test in progressive loading sequence have shown critical loads up to 25 N. Nanohardness indentation tests of the films have shown hardness around 200 HV with elastic modulus of 150 GPa. The friction properties of the coatings have been determined in a nano-tribological machine, with low loads in order to avoid substrate effect. Reasonable low friction coefficient values were observed for the deposited coatings compared to the bare substrates. The wear rates have been calculated and wear mechanisms of the films are discussed based on the SEM observation of the worn surface morphologies. Salt spray corrosion test performed for 96h on these films showed superior corrosion resistance for aluminum alloy substrates indicating cost effective sol-gel process as an alternative for aerospace applications.
2:50 PM		A2-7 Corrosion and Wear-Resistant Films on H-13 Nitrided Tool Steel Prepared by Reactive Non-Balanced Magnetron Sputtering A. Rojo, J. Acosta (ITESM, Mexico); J. Oseguera (ITESM-CEM, Mexico) Chromium and aluminum nitride films on H-13 nitrided steel were used to improve corrosion and tribomechanical resistance. Transition metal nitride layers CrN and AlN were tailored using non balanced magnetrons in a PVD system. Plasma spectral lines, identified by optical emission spectroscopy (OES), and electron density and electron temperature, measured by Langmuir probe, were identified and measured for several pressures and gas mixtures in the PVD reactor. The structural characterization of the layers by XRD, SEM, TEM and the corrosion test by means of potentiodynamic polarizations test were linked to the process parameters.