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Title: The transition from severe to mild wear in low alloy steels
Author: Sakrani, Samsudi B.
Awarding Body: University of Aston in Birmingham
Current Institution: Aston University
Date of Award: 1988
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The wear rates of sliding surfaces are significantly reduced if mild oxidational wear can be encouraged. It is hence of prime importance in the interest of component life and material conservation to understand the factors necessary to promote miId, oxidational wear, The present work investigates the fundamental mechanism of the running in wear of BB EN 31/EN 8 steel couples. under various conditions of load, speed and test duration. Unidirectional sliding experiments ,were carried out on a pin-on disc wear machine where frictional force, wear rate temperature and contact resistance were continuously monitored during each test, Physical methods of analysis (x-ray. scanning electron . microscopy etc.) were used to examine the wear debris and worn samples. The wear rate versus load curves revealed mild wear transitions, which under long duration of running, categorized mild wear into four distinct regions. a-Fe20s. Fe~04. FeO and an oxide mixture were the predominant oxides in four regions of oxidational wear which were identified above the Welsh T2 transition. The wear curves were strongly effected by the speed and test duration. A surface model was used to calculate the surface parameters. and the results were found to be comparable with the experimentally observed parameters. Oxidation was responsible for the transition from severe to mild wear at a load corresponding to the Welsh T~ transition. In the running-in period sufficient energy input and surface hardness enabled oxide growth rate to increase and eventually exceeded the rate of removal, where mild wear ensued. A model was developed to predict the wear volume up to the transition. Remarkable agreement was found between the theoretical prediction and the experimentally-measured values. The oxidational mechanism responsible for transition to mild, wear under equilibriurn conditions was related to the formation of thick homogenous oxide plateaux on subsurface hardened layers, FEO was the oxide formed initially at the onset of mild wear but oxide type changed during the total running period to give an equilibrium oxide whose nature depended on the loads applied.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Production and Manufacturing Engineering ; Mechanical Engineering