Effect of Inclusions on the Corrosion Properties of the Nickel-Based Alloys 718 and EP718

Metals

Andrey Karasev¹  PärG. Jönsson¹  Ekaterina Alekseeva²  Aleksey Alkhimenko² 

[1] Department of Materials Science and Engineering, School of Industrial Engineering and Management, KTH Royal Institute of Technology, Brinellvägen 23, 100 44 Stockholm, Sweden;Scientific and Technological Complex “New technologies and materials”, Institute of Advanced Engineering Technologies, Peter the Great Saint-Petersburg Polytechnic University, Polytechnicheskaya 29, 194064 Saint-Petersburg, Russia;

关键词: nickel-based alloys;    corrosion;    inclusions;    oil and gas industry;    electrolytic extraction;    alloy 718;   

DOI  :  10.3390/met10091177

来源: DOAJ

【 摘 要 】

Inclusions in steels and alloys are known to lower the resistance to deformation, as well as to lower the mechanical, corrosion and other properties. Studies of inclusions in nickel-based alloys are important since these materials could suffer from corrosion degradation in harsh operational conditions. This, in fact, could lead to a pitting initiation around the inclusions. Two industrial Ni-based alloys (alloy 718 and EP718) were investigated to determine the harmful effects of different inclusions on the corrosion resistance of Ni-based alloys. Specifically, the inclusion characteristics (such as composition, morphology, size, number and location) were determined for inclusions collected on film filters after electrolytic extraction and dissolution of a metal matrix around different inclusions on surfaces of metal samples after electrolytic extraction (EE). It was found that both Ni-based alloys contain various inclusion types: carbides (large size NbTi-C and small multicomponent carbides), nitrides TiNb-N and sulphides (TiNb-S in EP718 alloy). The most harmful effects on the corrosion resistance of metal were detected around sulphides and small carbides containing Mo, W, Cr. Dissolution effects were also observed around large carbides and nitrides, especially around inclusions larger than 10 µm. Moreover, the dissolution of a matrix around inclusions and clusters located on the grain boundaries were found to be 2.1–2.7 times larger compared to inclusions found inside of grains of the given alloy samples.

【 授权许可】

Unknown