A study of the behaviour for nickel base superalloys (Inconel 600 and hastelloy C-22)‎ in corrosive solutions and high temperatures oxidation

Other Title(s)

دراسة سلوك سبائك النيكل الفائقة (أنكونيل 600 و هيستالوي سي-22)‎ في أوساط تأكليه و الأكسدة في درجات الحرارة العالية

Dissertant

Hashim, Ammar Abd al-Karim

Thesis advisor

Hammadi, Nawal J.
Hammud, Ali S.

Comitee Members

Muhammad, Haydar Muadh
Atiq, Adnan A.
Nassar, Amin M.

University

University of Basrah

Faculty

Engineering College

Department

Department of Material Engineering

University Country

Iraq

Degree

Master

Degree Date

2014

English Abstract

The superalloys are nickel, iron-nickel, and cobalt alloys that contain large amounts of alloying elements have been produced to be used in corrosive environments and at elevated temperatures.

The purpose of the present work was to study the behavior of nickel base superalloys (Inconel 600 and Hastelloy C-22) depending on their main characteristics: the corrosion resistance in aqueous solution and the oxidation resistance at high temperatures.

The study of the corrosion resistance of alloys was investigated in different concentrations of hydrochloric acid solution (0.01, 0.05, 0.1, 0.5 and 1Mole) and different concentrations of sodium chloride (0.87, 1.75, 3.5, 4 and 5%) using polarization technique.

Tafel extrapolation method was used to determine the main corrosion parameters of studied alloys (Ecorr & Icorr) using Faraday's law to measure the corrosion rates of alloys in the corrosive solution.

An Artificial neural network (ANNs) model has been used to predict the corrosion polarization curve of alloys.

The input variables are the potential (E) and the concentration of corrosive solutions for HCl and NaCl; while the output variables (target) was the current density (i).

It was found that Hastelloy C-22 showed more corrosion resistance to corrosive solutions than Inconel 600, with increasing corrosion rates of both alloys with increasing the concentration of hydrochloric acid solution, while the corrosion rates of both alloys in sodium chloride reached a maximum value at 3.5% and then decreased when the concentration exceeded this value.

The predicted results of ANNs model showed good agreement with experimental values.

The study of oxidation resistant of alloys was carried out by determination of the oxidation rates of alloys at elevated temperatures and at ambient air.

The cyclic oxidation method was adapted by heating of alloys periodically in still air at 900, 1000 and 1100°C followed by cooling at ambient temperature.

The weight change measurement was recorded during the cyclic oxidation tests.

The X-ray diffraction and microstructure study were also used as characterization methods to illustrate the properties of studied alloys and oxide film that formed on the surface of oxidized alloys.

Inconel 600 and Hastelloy C-22 showed their ability to develop a uniform protective oxide film.

The oxide film that formed on both alloys was chromia oxide Cr2O3 with smaller amount of spinel oxide NiCr2O4.

The results of the weight gain measurements suggest that the oxidation kinetics of both alloys follows the parabolic behavior during the experimental tests.

Also both alloys, at 1100°C exhibited severe spallation of oxide film with linear decreasing in the weight change measurements.

The p-kp model with paralinear approximation was implemented to describe the subsequent cyclic process of oxide growth and spalling.

The obtained results of p-kp model showed the oxide growth associated with detecting the amount of metal consumed, spalling and the mass of adherent oxide.

The p-kp model had also developed a simple oxidation map.

Main Subjects

Materials Science , Minerals

Topics

• Oxidation
• Temperatures
• Corrosion
• Nickel alloys

No. of Pages

117

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-743643