Advanced surface-enhancement technology for decreasing wear and corrosion of equipment used for mineral processing D. Tao, R. Honaker, B.K. Parekh, C. Zhao and H. Han Associate professor, associate professor, associate director, student and graduate student, respectively, University of Kentucky, Lexington, Kentucky G. Engleman and N.B. Dahotre Student intern and engineer, respectively, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Graduate student and professor, respectively, University of Tennessee, Tennessee C. Blue Group leader, Oak Ridge National Laboratory, Oak Ridge, Tennessee Abstract Equipment wear and corrosion have significant adverse impacts on the operating cost and efficiency of mineral processing plants. In this paper, advanced surface-enhancement technologies are investigated to decrease the wear and corrosion rates of metal surfaces. Enhanced metal surfaces are achieved through surface conversion, enrichment and coating by use of an advanced high-density infrared (H Dl) plasma arc lamp. Studies were done to determine the effects o.f process parameters on surface properties and identify optimum conditions. The microstructure of the enhanced metal surfaces was characterized by SEM, EDS and microindentation. Laboratory wear testing was carried out to investigate the wear performance, and a viable coating candidate was determined. Key words: Equipment wear, Corrosion, Surface enhancement, Protective coatings Introduction The economic cost of wear on equipment is a serious problem in many industries. It is estimated that the annual cost associated with wear and corrosion in the United States is in excess of$IOO billion (Kazuhisa, 1998).1t has long been believed that wear and corrosion are the most common problems in the mineral processing heavy- equipment industry due to their significant impacts on material wastage and maintenance costs (Dunn, 1985). In the past two decades, research efforts have focused on reducing wear in cyclones, pumps, heavy medium vessels, etc .. However, little has been done to reduce the wear of screens, chains for conveyors and piping where ceramic lining is impractical. The screen opening in- creases as material wears, resulting in inconsistent aper- ture sizes and lower screening efficiency. This creates non-ideal feed to downstream operations, reducing their efficiencies. Frequent replacement increases equipment downtime and maintenance costs and reduces process efficiency. The development of advanced surface-en- hancement technology is of great interest to the mineral processing and coal preparation industries. The use of surface coatings is well established in engineering applications, and many coating techniques have been extensively studied (Dowson and Taylor, 1985). This paper describes the development of a new high- density infrared (HDI) process that enhances component surfaces for equipment used in mineral processing. The HDI method involves producing infrared heating with extremely high power densities of up to 3.5 kW/cm 2 using a unique plasma arc lamp (PAL) system. The PAL is shown schematically in Fig. I. Coating materials are fused by the PAL, yielding metallurgical bonding be- tween coating and substrate. Infrared heating is an inherently clean, noncontact heating method that provides rapid-response energy fluxes capable of heating rates in excess of 3,000°C/s, rapid power-level changes, rapid cooling rates and a control- lable temperature-gradient. It was demonstrated that the method could fuse and metallurgically bond coatings and steel substrates without convection mixing, providing a new means of rapid thermal processing of surface coat- ings (Engleman et aI., 2002). More detailed descriptions concerning the HDI equipment and process are found in Preprint number 05-045, presented at the SME Annual Meeting, Feb. 28-March 2, 2005, Salt Lake City, Utah. Original manuscript accepted for publication July 2005. Discussion of this peer-reviewed and approved paper is invited and must be submitted to SME Publications Dept. prior to May 31, 2006. Copyright 2005, Society for Mining, Metallurgy, and Exploration, Inc. MINERALS & METALLURGICAL PROCESSING 27 VOL. 23, NO.1' FEBRUARY 2006