Microstructural design of self-lubricating laser claddings for use in high temperature sliding applications

Nickel-based self-lubricating claddings with the addition of Ag and MoS2 were prepared by means of laser cladding on stainless steel substrates, aiming at their implementation in metal forming applications involving demanding tribological conditions at high temperatures. The novelty of this approach is the addition of MoS2 with the aim to achieve a uniform silver distribution within the resulting cladding by means of an encapsulation mechanism. This prevents it from floating to the surface during the deposition process and thus being subsequently lost during surface preparation. The role of Ag and MoS2 concentration on the encapsulation process is discussed in terms of phase composition and resulting microstructures. The tribological behaviour of the resulting laser claddings was evaluated at up to 600 degrees C under unidirectional sliding. The encapsulation of Ag leads to outstanding tribological properties while keeping the concentration of used Ag low, thus increasing the economic viability of the claddings. An improvement in terms of both friction and wear was observed for the self-lubricating claddings compared to the nickel-based reference alloy, thus making them good candidates for use in high temperature applications such as hot metal forming.