Temperature–load-dependent wear transitions of PH 15–5 stainless steel under dry sliding

Abstract

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.