Effect of PTA Current on Microstructure, Phase Constitution, Hardness and Dry-Sliding Wear of Fe–Cr–C Layers Deposited on 35L Cast Steel

Wear of crushing and grinding equipment components causes frequent maintenance and downtime; therefore, effective repair hardfacing routes are required to extend service life. This study investigates plasma transferred arc (PTA) surfacing of 35L cast steel using a high-chromium Fe–Cr–C powder (PG-S27) and clarifies how the welding current (40–120 A) governs layer geometry, microstructure, phase constitution, hardness, and dry-sliding tribological behavior. All deposits exhibited a dendritic–eutectic structure; increasing current led to dendrite coarsening, wider interdendritic regions, and deeper penetration/dilution. X-ray diffraction indicated an α-Fe matrix with chromium carbide phases (Cr7C3/Cr23C6), while the carbide-related signal decreased with higher current, consistent with enhanced dilution. The coatings showed a strong hardening effect compared with the substrate (~190 HV), reaching ~625–650 HV at 40–80 A and decreasing to ~556–589 HV at 100–120 A. In dry ball-on-flat sliding, the steady-state friction coefficient was nearly unchanged (μ ≈ 0.50–0.55) across all regimes; however, wear resistance depended strongly on current: the lowest wear was achieved at low-to-moderate currents (40–80 A), whereas higher currents (100–120 A) resulted in substantially increased material loss, approaching the substrate level. These results identify 40–80 A as the most favorable current window for obtaining wear-resistant PTA layers from PG-S27 on 35L steel.