The influence of femtosecond laser produced periodic surface textures on cutting tool friction

The performance thresholds of cutting tool geometries, tool materials and machining systems are often restricted by surface friction from work material engagement and flow across the tool surfaces. This study investigates the influences of geometrically defined surface textures of the tool rake face on forces encountered during two dimensional orthogonal turning. Regular textures featuring highly uniform profiles and inter-surface blending, exhibiting no measurable recast material were produced using a multi-scanning strategy of a femtosecond pulsed laser of near IR wavelength, in specially profiled flat rake faces of cemented carbide cutting tool inserts. A series of complementary tests were carried out on open ended grooved and equivalently sized closed dimpled surface textures of defined area ratios in the presence of a cutting fluid to investigate their effects on cutting and frictional forces when machining a Chromium steel material exhibiting ductile long chip behaviour. Data captured from a purpose designed in-situ lathe based friction test to simulate chip flow during machining, orthogonal turning experiments using a zero degree rake angle setup and laboratory tribometer oscillatory tests using an identical cutting tool and workpiece material tribo-pair and lubrication fluid, highlight the influences of closed and open structured textures on surface lubrication regimes and the consequent friction forces. The results of the study reveal that surface texturing of uncoated cemented carbide tool surfaces can reduce friction when employed with coolant within the tools' typical operating range. It has also been shown that textures having closed dimple structures produce the lowest friction forces under these conditions and reduced surface wear. The reduction of the measured surface friction produced by the dimpled textures also suggest desirable shifts in the boundary and hydrodynamic lubrication regimes towards the tools' cutting edge.