Friction and galling reduction potential of Ni-Ag-MoS2 coating by laser metal deposition at intermediate temperatures

Galling is a critical limitation in high-temperature forming of corrosion resistant and light-weight alloys such as austenitic stainless steel, aluminum, and titanium, as conventional lubricants rapidly degrade. This study investigates the anti-galling potential of a Ni-based self-lubricating alloy containing Ag and MoS₂, applied by laser metal deposition. The coating performance was benchmarked against conventional hot work tool steel using a load-scanning tribometer at room temperature and 150–300 °C against AA6082 aluminum alloy, AISI 316L austenitic stainless steel, and Ti6Al4V titanium alloys. The investigated Ni-based coating containing Ag and MoS 2 although not being able to completely eliminate use of solid lubricant in mid-temperature range, it provided markedly improved tribological behavior compared to reference tool steel. Against AA6082 and AISI 316L, friction was reduced by up to 50%, galling initiation loads increased by about 30%, and adhered counter-body material was suppressed by up to 60%. At elevated temperatures (150–300 °C), synergistic in-situ formation of Ag₂S, Cr₂S₃/Cr 3 S 4 , and Cr₂O₃ tribo-compounds on the contact surface effectively delayed work-material adhesion and transfer layer build-up. For Ti6Al4V, galling could not be completely avoided, but it was mitigated via thinner and more discontinuous transfer layers when using the Ni-based laser metal deposited coating, particularly at 300 °C. Multicycle tests confirmed extended stability of low-friction regimes and reduced accumulation of adhered material. These findings highlight that Ni-Ag-MoS₂ coatings deposited by laser metal deposition provide significant improvements in galling resistance and friction control, offering a promising route to extend tool life and reduce reliance on external lubricants in hot forming of corrosion resistant and light-weight structural alloys. • The load-scanning tribometer enables mapping of friction and anti-galling performance. • Ni5Ag10MoS coatings increase galling resistance by 30% and reduce friction by up to 50%. • Synergistic Ag- and Cr-sulphide tribofilms govern mid-temperature anti-galling behavior. • Suppressed adhesive wear is achieved in intermediate temperature range (up to 300 °C).