Microstructure evolutions and mechanical behaviors of Ni-based superalloy IN718 under hot corrosion conditions

Junyan Liang

doi:10.7273/000004183

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Microstructure evolutions and mechanical behaviors of Ni-based superalloy IN718 under hot corrosion conditions

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Microstructure evolutions and mechanical behaviors of Ni-based superalloy IN718 under hot corrosion conditions

Junyan Liang

Washington State University

Master of Science (MS), Washington State University

12/2017

DOI:

https://doi.org/10.7273/000004183

Handle:

https://hdl.handle.net/2376/124648

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Abstract

Heat resistant alloys--Oxidation

Nickel alloys--Microstructure

Heat resistant alloys--Microstructure

Heat resistant alloys--Corrosion

Heat resistant alloys--Mechanical properties

Heat resistant alloys--Thermal properties

Nickel alloys--Corrosion

Nickel alloys--Mechanical properties

Nickel alloys--Oxidation

This investigation was undertaken to evaluate oxidation and hot corrosion behavior of the Ni-based superalloy IN718, at 850 and 650°C, to explore its performance as turbine engine components under marine environment. Uncoated and different salt-coated samples (Type-A 75wt.% Na2SO4 + 25wt.% NaCl, and Type-B 90 wt.% Na2SO4 + 10 wt.% NaCl) were exposed in air at 850 and 650°C for up to 100 h. Weight loss was studied for both uncoated and salt-coated samples. light optical microscope, scanning electron microscopy, compression test, fatigue test and microhardness test were used to characterize the processed samples. A possible mechanism of corrosion, based on the corrosion compounds, is discussed. The variation in weight loss with time showed a parabolic growth of oxides. Coating with Type-A salt was found to be detrimental both at 850°C as well as 650°C. On the other hand, the Type-B salt mixture had small effect at 850°C; however, it was detrimental at lower temperature of 650°C. Type-B coatings of salt mixture caused very slow oxidation at both the temperatures. Increase in amount of NaCl salt coating was observed to enhance the rate of hot corrosion. From the microstructure, delta phase was found to be detrimental to the mechanical properties after 850°C hot corrosion. A Hall-Petch relationship between microhardness and average grain size for 650°C hot corroded samples was observed. Differences between 850°C and 650°C hot corrosion were discussed.

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Title: Microstructure evolutions and mechanical behaviors of Ni-based superalloy IN718 under hot corrosion conditions
Creators: Junyan Liang
Contributors: Qizhen Li (Advisor) - Washington State University, Mechanical and Materials Engineering, School of
Awarding Institution: Washington State University
Academic Unit: Mechanical and Materials Engineering, School of
Theses and Dissertations: Master of Science (MS), Washington State University
Publisher: Washington State University
Identifiers: 99900896440501842
Language: English
Resource Type: Thesis