Laser polishing - Enhancing surface quality of additively manufactured cobalt chrome and titanium components

Additive manufacturing (AM) allows construction of complex, free surface structures that cannot be produced as lone parts using traditional mechanical manufacturing. A commonly-used AM process is selective laser melting (SLM) where a high intensity laser beam selectively scans a powder bed according to the computer- Aided design of the component to be produced and the powder metal particles are melted into the required pattern. Unfortunately AM components show poor surface quality, in particular due to partially fused particles from the metal powder used in the AM process. As a result post processing of AM parts is essential to improve the quality of the surface to suit specific industrial needs. Currently SLM manufactured parts are chemically or mechanically polished, but both of these methods have their drawbacks. Mechanical polishing is limited by the complexity of the AM structure, whereas electrochemical polishing struggles if selective polishing of small areas is desired. The laser polishing process is based on the melting and subsequent solidification of a micro-layer of material, using a laser beam as the heat source for a smooth topography. As a result laser polishing offers a highly repeatable, short duration process that is capable of selective polishing of microscale areas. We are therefore presenting the possibility of using both pulsed and CW lasers to improve the surface quality of titanium and cobalt chromealloyAM parts toprovidetailoredaesthetic andtribological requirements. A range ofdifferent scan strategies, employing differentscanning directions, energy densitiesandspeeds, also different laser powersand spot diameters are investigated.