Effect of molybdenum on the microstructure and wear resistance of cobalt-base Stellite hardfacing alloys

• Published in: Surface & coatings technology 2003-03, Vol.166 (2), p.117-126
• Main Authors: Shin, Jong-Choul, Doh, Jung-Man, Yoon, Jin-Kook, Lee, Dok-Yol, Kim, Jae-Soo
• Format: Article
• Language: English
• Subjects: Applied sciences; Co-base Stellite alloys; Coating; Exact sciences and technology; Joining, thermal cutting: metallurgical aspects; Metals. Metallurgy; Microstructure and wear resistance; Molybdenum; PTA
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/S0257-8972(02)00853-8

The Stellite 6 hardfacing alloys with different Mo contents have been deposited on AISI 1045-carbon steel using a Plasma Transferred Arc (PTA) welding machine. The effect of Mo on the microstructures and wear resistance properties of the Stellite 6 hardfacing alloys were investigated using optical microscopy, scanning electron microscopy, electron probe microanalysis and X-ray diffraction. With an increase in Mo contents, the M 23C 6 and M 6C type carbides were formed instead of Cr-rich M 7C 3 and M 23C 6 type carbides observed in the interdenritic region of the Mo-free Stellite 6 hardfacing alloy. The size of Cr-rich carbides in interdendritic region decreased, but that of M 6C type carbide increased as well as the refinement of Co-rich dendrites. The volume fraction of Cr-rich carbides slightly increased, but that of M 6C type carbide abruptly increased. This microstructural change was responsible for the improvement of the mechanical properties such as hardness and wear resistance of the Mo-modified Stellite 6 hardfacing alloy.