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题目: 燃气轮机热端部件高强度高韧性扩散钎焊修复用新  型钎料和技术
报告人:国际焊接学会钎焊扩散焊专委会前主席Warren   Miglietti
时间: 2018年10月24日 星期三 13:30-15:00
地 点: 材料楼218会议室
主办单位: 材料科学与工程学院

个人简介:
Warren Miglietti is Consultant and Chief Metallurgist for his own company Miglietti and Associates, LLC, based out of Kansas City, Missouri, USA. He has 32 years of experience and expertise in the Welding, Brazing, FIC, Acid Stripping and Heat Treatment of Nickel and Cobalt base superalloys, as well as Titanium, Aluminum and Stainless Steels. His career has focused on developing repair techniques and processes for turbomachinery components for industrial, aircraft and aero-derivative components. He is chairman of the Commission XVII – “Brazing and Diffusion Bonding” of the International Institute of Welding (IIW). He has authored or co-authored the publication of 47 technical papers and has 15 repair technology patents. He was won numerous awards from the AWS, ASME/IGTI and IIW, including a few Best Paper Awards.


报告摘要:
Diffusion brazing has been used for over four decades to repair cracks and degradation on both aviation and land based turbine components. The objective of this work is to investigate and evaluate the use of hyper-eutectic Ni-Cr-Hf and Ni-Cr-Zr braze filler metals, where the melting point depressant is no longer B and/or Si but Hf and/or Zr, to avoid the forming of brittle intermetallic boride and silicide phases. For cracks greater than 0.15mm, a superalloy powder is mixed with the braze filler metal to enable wide cracks to be successfully brazed repaired. Both metallurgical and mechanical property evaluations were carried out. The metallurgical evaluation consisted of optical and scanning electron microscopy, and microprobe analysis. The diffusion brazed area consisted of a fine-grained equiaxed structure, with carbide phases,  dendrites, flower shaped/rosette eutectic phases and Ni7Hf2, Ni5HF, or Ni5Zr intermetallic phases. Hardness tests showed that the hardness values of the Ni-Hf and Ni-Zr intermetallic phases are 2.5-3.2 times softer than the Cr-boride intermetallic phases, so the LCF properties of the wide gap brazed joints are better. The mechanical property evaluations were tensile tests at both room temperature and elevated temperature, stress rupture tests from 760oC—1093oC and finally low cycle fatigue [LCF] tests. At the optimum braze thermal cycle; the mechanical test results achieved were a minimum of 80% and sometimes equivalent to that of the base metals properties.



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材料科学与工程学院