ICMCTF1999 Session G2-2: Scale-up, Manufacturing Aspects and Industrial Applications of Coatings

Tuesday, April 13, 1999 1:50 PM in Room Town & Country

Tuesday Afternoon

Start	Invited?	Item
1:50 PM		G2-2-2 Coating Restoration of Damaged Parts for Oil Processing Equipment I.C. Grigorescu, F. Denis, C. Di Rauso, D. Bello (PDVSA-INTEVEP, Venezuela) This paper presents an analysis of the practices of part restoration by metallurgical coatings, based on information compiled from oil refining units in Venezuela and USA. In all the visited units, parts restoration by coatings has an increasing incidence in the maintenance of rotating and reciprocating machinery; however the corresponding benefits seem to be poorly quantified. Coatings aimed at resisting corrosion and erosion-corrosion use to be carefully selected, mainly for the components of large compressor and turbines. In these cases, the design or selection of the coating is a matter of agreement between materials specialists belonging to the user, equipment manufacturer and/or repair shop; preliminary laboratory and field tests are performed to evaluate the fitness for operation of these coatings. Fewer cautions are taken when the worn area of tribological parts is rebuilt. The decision on the opportunity and modality of restoring is made in the shop and coating selection is governed by criteria of availability, which varies geographically. The assistance of materials specialists is infrequent, most of it occurring in cases of failure. Tribological variations induced by coating's presence, such as modifications of the load carrying capacity in bearing systems or different limits for lubricant contamination with metals, are not taken into account. Existing standards are not sufficient for the proper specification of restoration procedures, as compared with the documentation issued when static equipment are repaired by welding. Non destructive test methods for parts rebuilt by coating are particularly deficient.
2:10 PM		G2-2-3 Development and Applications of Chemical Vapor Deposited Polycrystalline Diamond L. Schäfer (Fraunhofer Insitute for Surface Engineering and Thin Films IST, Germany); M. Fryda (Fraunhofer Institute for Surface Engineering and Thin Films IST, Germany); J. Gäbler (Fraunhofer Institute for Surface Engineeringand Thin Films IST); T. Matthée (Fraunhofer Institute for Surface Engineering and Thin Films IST, Germany) High-grade products are of crucial importance for the industrial competiveness in the high-tech global market. The development and cost-effective fabrication of such products is often based on the development and utilization of high-performance materials. Within this context diamond is one of the outstanding materials because of its combination of a variety of extreme properties. However, the limited availability of diamond has been an obstacle for a wide-range application in production processes and high-grade products. In the last decade significant progress has been made in the area of activated chemical vapour deposition (CVD) of polycrystalline diamond films, increasing the availability of diamond considerably. Thermal activation by hot filaments (HFCVD) and electrical activation by DC and microwave plasmas (MWP) CVD, respectively, are commonly used for deposition of continious microcrystalline diamond films. Diamond can therefore be used for systems of relatively large dimensions and 3 dimensional complex shapes. Large-scale HFCVD and MWP-CVD processes have been developed in the last few years, thus making CVD diamond economically attractive. An insight in the mechanism of CVD diamond growth yields an assessment of the different deposition processes with respect to fabrication of CVD diamond products. The current status and high potential of CVD diamond technology with respect to the production of high-grade, innovative products can be demonstrated by prototypes and small-lot fabrication of CVD diamond cutting tools, sensors and optical components. Microtools with cutting dimensions below 1 mm used for machining of printed boards and microsystems demonstrate the capability for diamond coating on complex shape. Dry machining of lightweight materials, like for examble aluminum alloys, and precision grinding of corundum and glass using diamond coated tools are examples for meeting future demands on tools for high-quality as well as ecological and economical machining processes. Diamond coated electrodes have been developed using varaible high doping levels and large area HFCVD processes. They offer new opportunities in electrochemical synthesis and waste water treatment.