Wednesday, 26 February 2020 08:12

Department Oral Defense of Thesis/Dissertation

The PhD student (Zainab Azeez bati) discussed her thesis entitled ( Study the Improvement of Mechanical Properties of High Chromium Cast Iron by Isothermal Treatments). The thesis was held on the discussions hall / building C / Department of Materials Engineering / University of Technology on Thursday (23/01/2020). The discussion committee was formed of the teaching staff listed:

Names

Place

Position in the Committee

 

Prof. Dr. Alaa Abdul Hassan Atiya

University of Technology/ Department of Materials Engineering

Chief

Prof. Dr. Mona Khader Abas

University of Technology/ Department of production Engineering metallurgy

Member

Prof. Dr. Ahmed Oda Jasim

University of Babylon/ Department of Materials Engineering

Member

Prof. Dr. Omad Saadi Abdelkarim

University of Technology/ Department of Materials Engineering

Member

Assist. Prof. Dr. Muhsin Talib Mohamed

University of Kufa/ college of Engineering/  Department of production Engineering metallurgy

Member

Prof. Dr. Ali Hussein Otaiwi

University of Technology/ Department of Materials Engineering

Member-supervisor

Assist. Prof. Dr. Khadim Mutter shibeb

University of Technology/ Department of Materials Engineering

Member-supervisor

 Abstract

  Although some engineering materials are known for their superior properties in a particular field, this does not mean that they will not fail after certain periods when they are put into service. This means that they are far from perfection. For example, although high chromium white cast iron is known for its good resistance to wear, but also over time it is subjected to failure and this is what happens in the Kufa Cement Factory, which uses this iron as the liners of mills. Therefore, it is possible to conduct advanced scientific experiments to make its properties better than they were. So, five different heat treatments were applied to this type of cast iron to study their effect on the mechanical properties. These treatments are  annealing, air quenching , martempering treatments (using hydroxide mixture as cheaper alternative martempering medium for the ordinary nitrate martempering medium and make a comparison of the results between the two mediums) at different soaking intervals, cryogenic treatments (using three different cryogenic mediums) and cyclic annealing treatment. The hardness, toughness , erosion resistance and microstructure characteristics of this alloy before and after each treatment  were investigated. A slurry jet erosion apparatus was locally fabricated to measure the erosive resistance of this alloy. XRD, SEM, Vickers macro hardness, Charpy impact tests and the jet erosion apparatus were used to inspect the different effects of the different treatments used in this work. The results showed that each treatment affects differently on the microstructure and mechanical properties of this alloy. Some treatments enhance the hardness and erosion resistance, while others enhance the toughness. In martempering treatment by nitrate mixture , the percentage of hardness increment is approximately 53%, and the percentage of enhancement of erosion resistance is approximately 97.5%,  while in martempering treatment by hydroxide mixture , the percentage of hardness increment  is approximately 59% and the percentage of enhancement of erosion resistance is approximately 93%. For the cryogenic treatments, the hardness of the samples was lowered compared to the annealed samples but revealed a strange behavior in which that despite their low hardness, they depicted a remarkable erosion resistance. After further inspections it was found that the carbides which were drastically (dramatically) refined by cryogenic treatment, were returned to grow during the subjection to erosion stream, hence showed increment in hardness and improvement in erosion resistance. This means that the refinement of carbides by cryogenic treatments was metastable, but it causes a positive modification for these carbides. The best erosion resistance with a percentage of increase of approximately 91% was found. Cyclic annealing process lowers the hardness, toughness and erosion resistance of high chromium white cast iron. It was found also that there was a remarkable increase in the hardness values of about 64% compared to their counterparts that were not subjected to erosion stream because of the growth of carbides and modification of the microstructure after the subjection of samples to erosion stream.

Finally, it can be concluded that the better treatment processes that enhance the mechanical properties of high chromium white cast iron are martempering processes that come in the first place and then cryogenic treatments.

 The thesis was scientifically evaluated by Prof. Dr. Jasim Mohamed Salman / Babylon University / College of Engineering / Department of Materials Engineering, and linguistically by Assist. Prof. Dr. Sameer Ali Amen / University of Technology / Department of Mechanical Engineering. The thesis discussion was conducted in a scientific atmosphere and a PhD degree with grade of pass was awarded to the student after the completion of all the corrections that have been decided by the examiners.

Last modified on Wednesday, 26 February 2020 08:15

We have 72 guests and no members online

Top