Microstructure and Defects Analysis of As-cast HK40 and HH40 Heat-resistant Alloy Radiant Tube Elbow
Author of the article:LIU Dongfang;MENG Yu;ZHANG Huaxia;MA Guohong
Author's Workplace：Center of Melting&Casting,AECC Beijing Institute of Aeronautical Materials,Beijing 100094,China
Key Words：heat resistant steel DSC micro-porosities microstructure carbide type
Abstract：Taking HK40 and HH40 alloy as the research object,the microstructure and defects of two kinds of radiation tube elbow were analyzed,and the types and distribution of the defects were discussed.The results show that the as-cast microstructure of HK40 is austenitic and eutectic with skeleton-like carbide,and the main type of carbide is M7C3.The structure of as-cast HH40 alloy is composed of austenite,a small amount of ferrite,and a mixture of austenite and carbide.The carbide types are mainly M23C6 and a small amount of M7C3.The typical defects of HK40 and HH40 alloy industrial radiant tube elbow castings are all microporous,and the porosity is the most serious in the middle of the wall thickness.The looseness in the most serious area of HK40 and HH40 alloy radiant pipe elbow reaches grade 12 and grade 3,respectively.Compared with HH40 alloy,HK40 alloy has a wider solidification interval and a greater tendency to loose.
