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Open AccessArticle

Wear Behavior of Austempered and Quenched and Tempered Gray Cast Irons under Similar Hardness

by Bingxu Wang 1,2, Xue Han 2, Gary C. Barber 2 and Yuming Pan 2,*,†
1
Faculty of Mechanical Engineering and Automation, Zhejiang Sci-Tech University, Hangzhou 310018, China
2
Automotive Tribology Center, Department of Mechanical Engineering, School of Engineering and Computer Science, Oakland University, Rochester, MI 48309, USA
*
Author to whom correspondence should be addressed.
Current address: 201 N. Squirrel Rd Apt 1204, Auburn Hills, MI 48326, USA.
Metals 2019, 9(12), 1329; https://doi.org/10.3390/met9121329
Received: 14 November 2019 / Revised: 3 December 2019 / Accepted: 4 December 2019 / Published: 8 December 2019
In this research, an austempering heat treatment was applied on gray cast iron using various austempering temperatures ranging from 232 °C to 371 °C and holding times ranging from 1 min to 120 min. The microstructure and hardness were examined using optical microscopy and a Rockwell hardness tester. Rotational ball-on-disk sliding wear tests were carried out to investigate the wear behavior of austempered gray cast iron samples and to compare with conventional quenched and tempered gray cast iron samples under equivalent hardness. For the austempered samples, it was found that acicular ferrite and carbon saturated austenite were formed in the matrix. The ferritic platelets became coarse when increasing the austempering temperature or extending the holding time. Hardness decreased due to a decreasing amount of martensite in the matrix. In wear tests, austempered gray cast iron samples showed slightly higher wear resistance than quenched and tempered samples under similar hardness while using the austempering temperatures of 232 °C, 260 °C, 288 °C, and 316 °C and distinctly better wear resistance while using the austempering temperatures of 343 °C and 371 °C. After analyzing the worn surface, abrasive wear and fatigue wear with the presence of pits, spalls, voids, long cracks, and wear debris were the main mechanisms for austempered gray cast iron with a low austempering temperature. However, only small pits and short cracks were observed on the wear track of austempered gray cast iron with high austempering temperature. Furthermore, the graphite flakes were exposed and ground by the counterpart surface during wear tests. Then, the graphite particles would form a tribo-layer to protect the contact surface. View Full-Text
Keywords: AGI; QTGI; abrasive wear; fatigue wear; graphite tribo-layer AGI; QTGI; abrasive wear; fatigue wear; graphite tribo-layer
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Wang, B.; Han, X.; Barber, G.C.; Pan, Y. Wear Behavior of Austempered and Quenched and Tempered Gray Cast Irons under Similar Hardness. Metals 2019, 9, 1329.

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