报告人：Dr. Zhou (Joe) Gang (Chief metallurgist)

主持人（邀请人）： 任振安 教授

报告时间：2019年5月20日9：00-10：30

报告地点：南岭校区机械材料馆209学术报告厅

主办单位：尊龙凯时材料科学与工程学院、汽车材料教育部重点实验室、材料连接团队

摘要：

Welds between engineering alloys of differing composition and thermo-physical properties, commonly referred to as Dissimilar Metal Welds (DMWs), are an integral part of the equipment used in many advanced industrial processes, such as supercritical power plants and HRSGs. The great majority of DMWs are made to join components that operate at low or moderately elevated temperatures relative to the melting range of the alloys involved, and these welds routinely operate for long periods of time without incident. However, DMWs also are used in pressure part fabrication to join austenitic tubes or pipes to ferritic tubes or pipes or join austenitic non-pressure part attachments to a ferritic tube or pipe. In these cases, the components of which the DMW is a part typically operate under conditions where creep damage coupled to the effects of frequent cycling is expected to influence the service life of the weld. Under these conditions, the performance of DMWs has been far less predictable. For example, the service history of DMWs made between low alloy ferritic tubing (e.g., Grade 22) and tubing fabricated from one of the 300-series austenitic steels (e.g., TP304H) and installed in superheaters (SH) or reheaters (RH) of large power boilers has been highly variable, depending critically on the choice of filler metal and, in certain cases, on the operating profile of the boiler. The reasons for the variability in performance now are understood to involve differences in the thermo-physical properties of the materials being joined as well as differences in local mechanical properties as these are altered by diffusion-driven compositional changes along the dissimilar metal interface. For the SH and RH DMWs, the response to the spate of early weld failures, where the weld was made using an austenitic stainless filler metal, was to switch to a nickel-base filler metal that minimized the incompatibility in the thermo-physical properties and reduced the local mismatch in mechanical properties by limiting the amount of carbon diffusion from the low alloy tubing into the more highly alloyed filler metal. The resulting two-to-threefold increase in the average service life of the DMWs underscored the basic soundness of the approach.

报告人简介：

Dr. Zhou (Joe) Gang, Chief Metallurgist, ATC-CES, USA

Dr. Zhou has over 30 years of diverse experience in failure analysis and condition assessment of power-generating equipment and industrial equipment, welding metallurgy and technology, welding repair, weldability testing and design, creep testing and design, corrosion testing and design. In addition, Dr. Zhou is the expert in metallographic & fractographic examination and microstructural interpretations as related to critical boiler and turbine components. Prior to joining ATC-CES, Dr. Zhou served as a Principal Metallurgical Engineer for Alstom and Alstom/GE. He is a member of ASM and AWS and had published over 40 papers and over thousands of failure analysis and R&D reports. Recently, Dr. Zhou has been working on:

(1)Metallurgical Understanding of Gr 91 DMW Failures

(2)Methodology to Characterize Grade 91 Metallurgical Condition

(3)Low Creep Ductility Issue of CSEF steels

(4)Cracking of T23 Components