AVS 58th Annual International Symposium and Exhibition
    Tribology Focus Topic Thursday Sessions
       Session TR-ThP

Paper TR-ThP1
Subsurface Characteristics of an Abraded Fe-0.4wt%C Martensitic Steel using Nanoindentation and Cross-Sectional TEM Techniques

Thursday, November 3, 2011, 6:00 pm, Room East Exhibit Hall

Session: Tribology Focus Topic Poster Session
Presenter: Futoshi Katsuki, Sumitomo Metal Industries, Limited, Japan
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The present investigation of unidirectional abraded surfaces of a martensitic (0.4 wt%C) steel with silicon (1.5wt%Si), chromium (1.5wt%Cr) and molybdenum (1.9wt%Mo) addition elucidates the work hardening and the softening near the surface layer caused by abrasion, particularly its relation to the wear behavior. The abrasion testing was performed using a pin-abrasion apparatus in which a small pin of the specimen was ground on an abrasive paper at an applied load of 2.1N and sliding speed of 0.66m/s. Crushed silica particles (size: 15-67μm) were used as the abrasive medium. The abraded surfaces were examined with a nanoindentation apparatus to evaluate the variation of nanohardness with sliding time on a nanometer scale. A cross sectional transmission electron microscope (TEM) technique was also employed to clarify the structural changes in the region close to the abraded surface. It has been found that abrasion induced work hardening with sliding time was observed in the case of chromium and molybdenum addition steels. A fine dispersion of molybdenum carbide (Mo2C) was observed in the surface of the molybdenum steel after abrasion. Mo2C precipitates at approximately 550°C, indicates that surface and near surface temperatures would be over the carbide formation temperature by the abrasion induced frictional heating. On the other hand, the softening has been indicated to be caused by the abrasion heating leading to some tempering effects in the case of the silicon addition steel. Work hardening and softening caused by abrasion induced subsurface deformation and frictional heating respectively seem to be two processes taking place simultaneously which counteract each other's effect. Metallurgical reaction such as precipitation and temper by frictional heating has been found to play a important role in controlling the wear characteristics of steels. The influence of the alloying element addition on the wear response of the martensitic steel will be discussed.