Wear in hard metal check valves: In-situ surface modification through tribolayer formation in dry contact

Abstract

Tools in injection moulding units, especially the check valves, can suffer dry hard metal - hard metal contact under severe conditions, thus experiencing increased wear. For the present study, various hard metal pairings were investigated using dry pin-on-disc tests to simulate the tribosystem of the check valve. Hard metal discs with WxC particle sizes between ~0.9 and 3 μm and binder contents between 9 and 17.5 wt. %, were tested against similar pins with smaller WxC particles. Results show that the cracking of carbides is the major wear mechanisms and that decreased WxC particles sizes together with decreased binder contents lead to lower wear rates. The combination of the hard metal with the smallest WxC particles and the lowest hardness differences between pin and disc leads in this case to a beneficial material transfer and tribolayer formation, resulting in increased wear resistance of both sliding counterparts, promising a lifetime enhancement of the check valves.