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司太立合金激光制造在耐磨中的应用

演讲课题：司太立合金激光制造在耐磨中的应用

演讲人：刘蓉

演讲摘要：

Stellite alloys are a range of cobalt-chromium alloys. It may also contain tungsten or molybdenum and a small (less than 3 wt%) but important amount of carbon. Therefore, Stellite alloys are generally strengthened by the precipitation of carbides in the cobalt solid solution matrix. Laser cladding with Stellite alloys has found a wide range of applications across industries, for example, high pressure gas turbines, diesel engine valves, drainage plough blade, aerospace, deep drawing tool, mining support braces, hydraulic cylinder hardfacing, and stainless steel runners. Hardfacing of components may provide the best solution in situations where wear is localized or where the best material is difficult to cast. Various Stellite alloys and hardfacing processes enable producing a targeted coating approach to solve difficult wear problems. Laser cladding process offers many advantages to produce Stellite alloy hardfacing, which include minimal dilution due to low heat output, controlled energy supply possible, high heating and cooling rates for better microstructure, no tool wear, compact technology, providing superior results of hardness, homogeniety, purity, and microstructure. However, there are many challenges in producing desired Stellite alloy laser cladding. For example, Stellite 3 (30.5%Cr, 12.5%W, 2.4%C, in weight) with very high carbon content is promising for hardfacing material because of its high hardness and excellent wear resistance. It is commonly employed in severe wear conditions, for instance, it is a good candidate for the hardfacing of metal to metal sealing valves where high hardness and wear resistance are required, but it has a serious problem - cracking during laser processing, due to its extreme brittleness. To solve this problem, attempt was made to create a mixed powder of major Stellite 3 with minor Stellite 21. Stellite 21 (27%Cr, 5.5%Mo, 0.25%C, in weight) has better ductility among Stellite alloys owing to its very low carbon content. It also exhibits good work hardening property from its cobalt solid solution since the carbide volume fraction of this alloy is very low. It was shown that no cracks and pores were formed in the laser cladding containing Stellite 3 (70 wt%) and Stellite 21 (30 wt%) on 316 stainless steel substrate. This new alloy is expected to be applied for the sealing surfaces of valves.

刘蓉

加拿大卡尔顿大学机械航空系教授

Dr. Rong Liu is a professor of the Department 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 as well as manufacturing of superalloys and their composites, 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, in a total amount about $1.66 million. She has published 120 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 overseas expert professor, awarded by Zhejiang University of Technology, China, in collaboration with Zhejiang Provincial Collaborative Innovation Center of High-End Laser Manufacturing Equipment.

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