Temperature–Load‐Dependent Wear Transitions of PH 15–5 Stainless Steel Under Dry Sliding

The dry sliding behavior of PH 15–5 precipitation‐hardened stainless steel was investigated at room temperature and −40 °C under 10 and 20 N using reciprocating ball‐on‐disc tests. A 6 mm WC–Co ball was used at 34 mm s −1 for 30 min, corresponding to 61.2 m sliding distance. Friction, wear volume, surface morphology, elemental distribution, phase constitution, topography, and room‐temperature nanoindentation response were evaluated. The H1025‐aged steel exhibited a predominantly lath‐martensitic morphology, a hardness of ~4.15 GPa, and a reduced elastic modulus of ~220 GPa. At 10 N, −40 °C produced lower wear volume and a shallower track than room temperature despite a higher steady‐state mean coefficient of friction (CoF). At 20 N, −40 °C yielded the highest steady‐state mean CoF, temporal variability, wear volume, and track depth, together with extensive cracking, deep grooves, coarse debris, and large delaminated regions. Room‐temperature wear showed surface smearing, localized adhesion, and more uniformly distributed oxygen‐rich regions. The low‐temperature morphology is consistent with crack‐assisted delamination; however, without cross‐sectional characterization or low‐temperature fracture testing, crack‐initiation depth and propagation path could not be established. The results show that the sub‐zero response depends strongly on applied load and cannot be inferred from friction magnitude alone.