Sliding wear performance of metallic laser coatings against composite PTFE seals

Laser coatings are frequently used in applications where they slide against various elastomeric and polymeric seals or guide bands in different environments. Examples of such applications include hydraulics, maritime propulsion systems and components in pulp & paper industry. In this study highly corrosion resistant Inconel 625 (DIN Mat. No. 2.4856) and Thermanit 2509 super duplex stainless steel (~1.4501) coatings manufactured by novel coaxial hot-wire laser cladding technique are tested in dry conditions at room temperature against various composite polytetrafluoroethylene (PTFE) seals. Despite only small difference in coating surface hardness, ~1.4501 and 2.4856 show significant differences in wear and friction performance against various seals. For instance, ~1.4501 is superior to 2.4856 against glass fiber and MoS2 reinforced PTFE in terms of wear resistance and friction characteristics, whereas 2.4856 performs better against bronze reinforced PTFE seal. The reference Stellite laser coating, which is the hardest counter surface in this study, exhibits the best wear behavior against all the seal materials tested. The differences in wear performances are explained by cohesive and adhesive wear mechanisms.