Wear is a well-known problem in injection molding, especially when dealing with fiber reinforced materials.
Fiber-reinforced polymers allow for implementation of plastic materials in structural components. However, increasing
glass-fiber content in polymer melts up to 50 wt% causes accelerated component wear in injection molding machines,
sprues, hot runner systems and tools. In this contribution the focus will be on abrasive wear. While testing high grade steels
for their wear behavior a phenomenon was discovered. By varying the injection rate in the platelet-wear tester up to highest
possible values (56 cm³/s up to 210 cm³/s) we measured for the first time that even powder metallurgical steels with a
Rockwell hardness of 62 HRc could be soft annealed over a series of 210 injection shots down to a hardness of 43 HRc.
The hardness decrease was detectable down to 0.9 mm distance from the surface. The suspected cause for this decrease in
hardness is a change in micro-structure due to strong viscous dissipation. To cause a loss of hardness, temperatures over
550°C have to occur on the steel surface. To further test and understand this phenomenon, a new testing apparatus based
on the well-known platelet wear tester was invented and built. The new testing apparatus will be presented, and its
measuring capabilities will be disclosed. Furthermore, we will show first measurement results regarding the temperature
rise inside the steel platelets that prove temperatures above 550°C. In addition to that, machine data that was recorded
during testing, will be disclosed to put the results when the phenomenon was first measured into the right light.