Sintered hardmetals with iron–manganese binder

Abstract

A powder of tungsten carbide WC was mixed with 20 or 50 mass-% of atomised binder powder consisting of iron alloyed with 22 mass-% manganese and sintered at 1300°C. The constitution was calculated with the Thermo-Calc program using the database TCFE6 and compared to the microstructure analysed by light optical microscopy, X-ray diffraction, SEM with EDX and electron backscattered diffraction. The materials 50∶50 and 80∶20 (WC/binder in mass-%) fell just short of the two-phase region of WC+γ and η-M₆C appeared. The addition of 1 mass-% graphite shifted 80∶20∶1 beyond this region and entailed M₃C cementite. The hot hardness was too low to consider cutting applications. Therefore, the resistance to abrasion by mineral particles was investigated at room temperature by single and multiple scratch tests and by pin on plate wear tests. The good wear resistance is due to the high hardness and size of η-carbides and the intensive cold workhardening in the wear surface, which was supported by transformation induced plasticity and revealed by focused ion beam TEM.

Keywords:

• Sintered hard metal
• Iron–manganese binder
• Constitution
• Microstructure
• Hot hardness
• Wear resistance

This work was initiated by Professor Dr-Ing A. R. Kaysser-Pyzalla at the Max-Planck-Institute in Düsseldorf. The authors are grateful to Dr J. Garcia for his assistance.