Influence of Viscous Dissipation on Wear Behavior and Hardness Evolution of Tool Steels in Glass‐Fiber‐Reinforced Polymer Processing

This study investigates the influence of viscous dissipation on the wear behavior and near‐surface hardness of five tool steels during injection molding of glass‐fiber‐reinforced PA66. Wear tests are performed at two injection volume rates (IVR: 100 and 300 cm 3 s −1 ), supported by temperature monitoring, hardness profiling, and microscopic surface analysis. At low IVR, all steels show wear values below 0.4 mg with no detectable hardness loss, indicating suitability for long‐term use under moderate conditions. Clear differences emerge at high IVR: the conventional steel X153CrMoV12‐1 exhibits severe wear, while powder‐metallurgical steels (X270CrVMo20‐7‐1, X190CrVMo20‐4‐1, HS6‐5‐3‐8) display superior resistance. X270CrVMo20‐7‐1 shows the highest robustness, whereas X190CrVMo20‐4‐1 suffers pronounced hardness loss and stronger wear, performing similarly to HS6‐5‐3‐8 but through different mechanisms. X190CrVMo20‐4‐1 relies on carbides at the expense of matrix stability, whereas HS6‐5‐3‐8 retains wear resistance through its inherently high hardness, unaffected by viscous dissipation. The results demonstrate that wear resistance in polymer processing is governed not solely by carbide stability or matrix hardness, but by their interplay under thermomechanical loading. Viscous dissipation acts as a decisive factor amplifying material differences. These findings offer guidance for steel selection and provide evidence to refine wear models, especially for fiber–surface interactions and temperature‐dependent material responses.