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THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING
GEORGIA INSTITUTE OF TECHNOLOGY
Under the provisions of the regulations for the degree
DOCTOR OF PHILOSOPHY
on Monday December 2, 2019
2:00 PM
in MRDC 4211
will be held the
DISSERTATION PROPOSAL DEFENSE
for
Chuchu Zhang
"Wear Rate and Mechanism Maps for Stainless Steel at High Temperature”
Committee Members:
Prof. Richard Neu, Advisor, MSE/ME
Prof. Preet Singh, MSE
Prof. Joshua Kacher, MSE
Prof. Jeffrey Streator, ME
Prof. Shreyes Melkote, ME
Abstract:
Contacting interfaces moving in a back and forth way relative to each other at high temperature is found in mechanical systems like internal combustion engine, aerospace propulsion system, energy generation system and metalworking equipment. The working temperature for components in such mechanical systems, for example, pivot-vanes/ring in variable geometry turbocharger (VGT, also called variable-nozzle turbine, VNT) for diesel engines can vary from ambient temperature to 700, and even higher for gasoline engine. Materials selection for low friction, low wear in high temperature applications is a complex problem because of the many influence factors and coupling effects especially when friction and wear control methods like lubricating cannot be used.
It was found that a compacted and sintered wear protective layer, namely “glaze layer” can be formed in many Co, Ni and Fe alloys under certain circumstances, and it is possible to take advantage of glaze layer formation to reduce friction and wear at high temperature. The proposed research is aimed for better understanding on kinetics of glaze layer formation and retention, and shed light on practical methodologies for the materials selection and contact surface design for unlubricated high temperature fretting and reciprocating sliding contacts with the help of wear mechanism map. 310S austenitic stainless steel is chosen as a sample system to generate temperature-frequency wear mechanism map that covers considerably large temperature and frequency in its working condition than has previous been considered. The data set will also be used to test the applicability of a newly proposed critical cycle () model for glaze layer formation. In addition, the dynamic influence when cycling between conditions involving two distinct wear mechanism zone will be investigated with cyclic temperature and frequency test methodology. The new map for 310S austenitic stainless steel will be compared to that of 304 austenitic stainless steel, the most studied austenitic stainless stain, to probe the influence of elemental composition (Cr and Ni) on shaping the wear map for high temperature applications
