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    Evaluation of Optimal Economic Life of Cemented Carbide Tool Turning AISI4340
    (İstanbul Gelişim Üniversitesi Yayınları / Istanbul Gelisim University Press, 2017-11-13) Dahunsi, Olurotimi Akintunde; Awopetu, Olayinka Oladele; Ogedengbe, Tunde Isaac; Mohammed, Tiamiyu Ishola; Adamolekun, Taiwo Micheal
    As turning operation proceeds on a lathe machine, it is required that sufficiently good surface quality be achieved if all the affecting parameters, including tool geometry are held constant. In this paper, the effect of tool geometry variation due to wear in the case of C6 cemented carbide tool on AISI 4340, was studied. Using surface roughness as yardstick for estimating the point beyond which the maximum economic utilization derivable from the tool is hampered, it was realized that each insert should be replaced after ten minutes of turning operation to retain their optimum usefulness. The tool wear parameters were found to be in linear relationship with the cutting time, while the average surface roughness was modelled nonlinearly using an exponential function. A fourth degree polynomial approximated the trend for the cutting force. Sharp deflections were observed on the surface roughness and cutting force graphs after the tenth minute. Generally for the entire cutting time, the measured cutting force increased by about 33% while the flank wear width and crater wear width increased by 170% and 56% respectively. Surface roughness also increased by about 130%.
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    Prominence of Hadfield Steel in Mining and Minerals Industries: A Review
    (İstanbul Gelişim Üniversitesi Yayınları / Istanbul Gelisim University Press, 2017-06-28) Okechukwu, Chijioke; Dahunsi, Olurotimi Akintunde; Oke, Peter Kayode; Oladele, Isiaka Oluwole; Dauda, Mohammed
    High manganese austenitic steel, popularly called “Hadfield steel” has dominated and played significant role in wear applications, especially in the mines and minerals industries since its invention over a century ago. A review on the researches on this steel revealed that its prominence in these fields is mainly due to its good combination of impact and abrasion wear resistance arising from its high toughness and high hardness respectively. Its strain hardening ability under impact loading is evidenced by increase in hardness as the material work hardens; this lowers the amount of wear in service. The work hardening property of the steel has been linked to governing mechanisms such as dislocation, deformation twinning, and dynamic strain ageing; also, it is enhanced by increase in carbon, ageing temperature and reduction in manganese content. Carbide precipitation along the grain boundaries and within the grains is the major cause of embrittlement of the steel. These carbides together with voids and porosities during casting solidification, improper heat treatment, overheating during welding, use of unsorted scrap metal and wrong wear application have been identified as the causes of premature failure in service. Hardfacing method has been proposed as a means of substituting the steel in wear applications, as alternative wear materials such as white cast iron and austempered ductile iron lack the combination of impact and abrasion resistance being offered by the Hadfield steel.