Comparative Study of the Microstructure, Local Elemental Composition, Microhardness, and Dry-Sliding Friction Behavior of Co-Cr-W, Fe-Mn-C, and Fe-Cr-Ni-Mn GTAW Deposits on 09G2S Steel

This study systematically evaluates the microstructural characteristics, cross-sectional microhardness profiles, and dry sliding friction dynamics of Stoodite 6-M, AISI 1065-type (Np-65G, GOST 10543-98), and AISI 307-type stainless steel (Sv-08Cr20Ni9Mn7Ti, GOST 2246-70) coatings deposited on 09G2S low-alloy steel via gas tungsten arc welding (GTAW). Microstructural evolution and elemental distributions were characterized using optical microscopy and SEM/EDS, while functional properties were assessed via cross-sectional Vickers microhardness profiling (HV0.05) and rotary ball-on-disk friction testing. All surfacing systems produced sound, defect-free fusion interfaces, developing cobalt-matrix dendritic, acicular/packet-lath, and fine cellular-dendritic austenitic structures for Stoodite 6-M, AISI 1065, and AISI 307, respectively. The core cladding microhardness peaked in AISI 307 (505 ± 18 to 525 ± 20 HV0.05), which may be associated with its alloy composition and observed microstructural features, followed by Stoodite 6-M (445 ± 15 to 468 ± 12 HV0.05) and AISI 1065 (355 ± 14 to 438 ± 16 HV0.05). Tribological signal analysis revealed a distinct divergence between static mechanical strength and kinetic sliding behavior: AISI 1065 demonstrated the lowest mean steady-state friction coefficient following initial running-in (μmean = 0.532, SD = 0.019–0.023, CV = 3.57–4.28%), whereas Stoodite 6-M exhibited a higher steady-state friction coefficient (μmean = 0.613, SD = 0.022–0.026, CV = 3.60–4.20%) alongside superior running-in stability, and AISI 307 recorded an intermediate value (μmean = 0.566, SD = 0.035–0.041, CV = 6.19–7.17%). These findings demonstrate that microhardness, mean friction force, and signal stability operate as uncoupled material selection parameters. The study defines baseline friction performance under dry contact conditions, emphasizing the necessity of evaluating contact kinetics independently from bulk mechanical hardness.