Surface Finishing and Preparation
This is the collective name given to altering the surface of a component or structure and can be undertaken in a myriad of ways – from mechanical abrasion, grinding, laser or flame etching and acid and chemical removal to water profiling, particle bombardment or blasting.
The blasting concept in turn encompasses a diverse range of processes from bead and shot blasting to, even, traditional sand blasting – strictly, today, an illegal process given the health impacts arising from the use of sand and its associated silicosis. Alternatively, grit blasting, using an angular abrasive media, from those suitable for ‘once only’ use – such as glass grits, expendable abrasives including copper and coal slags – to more durable products like garnets, aluminium oxides, silicon carbides, cast or chilled iron grits, steels and stainless steel products achieves the same result, altering the surface for a specific reason via the impact or wear characteristics of the particle moving over or past the component’s surface.
In a blasting environment the altering of the media flow rates, air pressure distance from the component and angle of attach at the surface are all variables that can have a major impact on the surface finish. Controlling these processes and utilising a spherical or round media for bombardment changes the blasting concept to a peening concept. In so doing this also limits the amount of surface removal achieved and offers a different effect, both cosmetically and structurally. The effect of bombarding the surface of a metal (predominantly) with spheres imparts a hammering effect and can significantly improve the stress fatigue of components. This is a process extensively used in the aerospace and automotive sector for improving gear, spring, turbine blade and airframe component life.