Seminar - Development and Performance Characterization of
Cobalt-Based Superalloys By Dr. R. Liu
Date: 16 March 2015 (Monday)
Time: 11:00 am – 12:00 pm
Venue: EF305, The Hong Kong Polytechnic University
Superalloys are a family of high performance alloys and can be divided into three major classes: ironbased, nickel based, and cobalt-based. Stellite alloys and Tribaloy alloys constitute the main categories of cobalt based superalloys. Owing to the unique chemical compositions, these alloys display exceptional properties including high-temperature strength, wear/erosion and corrosion/oxidation resistance and are widely used in various industries. This presentation will give an overall review of research on Stellite alloys and Tribaloy alloys with focus on microstructure, corrosion and wear/erosion resistance as well as their applications. Stellite alloys are a range of cobalt-chromium alloys. They may also contain tungsten or molybdenum and a small (< 3 wt%) but important amount of carbon. Therefore Stellite alloys are generally strengthened by the precipitation of carbides in the cobalt solid solution matrix. Tribaloy alloys are a series of wear resistant nickel- or cobalt-based alloys, containing a large volume fraction of a hard, intermetallic Laves phase in a much softer matrix. It is the presence of this large volume fraction of Laves phase that enables these materials to resist wear under poor or unlubricated conditions. The main alloying elements in Tribaloy alloys include molybdenum and chromium. Silicon is a minor (~ 3 wt%) constituent of Tribaloy alloys, but molybdenum and silicon are added at levels in excess of their solubility limit in order to induce the precipitation of the Laves phase. The carbon content in Tribaloy alloys is kept low to avoid carbides forming in preference to the Laves phase. Several new Stellite alloys and Tribaloy alloys with improved properties have been developed in recent years. The research results on both conventional and newly developed Stellite alloys and Tribaloy alloys are reported and discussed.
Dr. Rong Liu is a professor of the Department g p p of Mechanical and Aerospace Engineering, Carleton University, Canada. She received a Bachelor degree of mechanical engineering from Northeastern University, China, in 1983; a Master degree of mechanical engineering from Northeastern University, China, in 1990; a Master degree of materials engineering from University of Wollongong, Australia, in 1995; a Ph.D. degree of mechanical engineering from Deakin University, Australia, in 1998. She worked in the Department of Chemical and Materials Engineering, University of Alberta, Canada, as postdoctoral fellow from 1998 to 2000, and then joined the Department of Mechanical and Aerospace Engineering, Carleton University, Canada, as assistant professor in 2000, promoted to associate professor in 2005 and full professor in 2012.
Dr. Rong Liu has established research programs in development and performance characterization of superalloys and their composites, as well as various superalloy coatings, in collaboration with Kennametal Stellite Inc. — the industry leader specialized in producing high temperature wear/corrosion resistant superalloys and coatings, and with the Institute for Aerospace Research, National Research Council Canada (NRC), since 2000. She received research funds from various programs of Natural Sciences and Engineering Research Council (NSERC) and from other sources including federal, Ontario provincial grants and industry supports. She has published more than one hundred articles in journals and conference proceedings. She has also contributed a book chapter: Chapter 4 High Temperature Wear/Corrosion Resistant Stellite Alloys and Tribaloy Alloys, in CRC Handbook on Aerospace and Aeronautical Materials, CRC Press, Taylor & Francis, July 2012. She is a member of the American Society for Metals (ASM), USA and a member of the Professional Engineers of Ontario (PEO), Canada. She was awarded by Carleton University Research Works in 2009. She is also an oversea distinguished professor, awarded by Zhejiang University of Technology, China, in collaboration with Research Center of Laser Processing Technology and Engineering.