The topographic development and areal parametric characterization of a stratified surface polished by mass finishing

Massfinishing is amongst themost widely usedfinishing processes inmodernmanufacturing, in applications fromdeburring to edge radiusing and polishing. Processing objectives are varied, ranging from the cosmetic to the functionally critical. One such critical application is the hydraulically smooth polishing of aero engine component gas-washed surfaces. In this, andmany other applications the drive to improve process control and finish tolerance is ever present. Considering its widespread use massfinishing has seen limited research activity, particularly with respect to surface characterization. The objectives of the current paper are to; characterise themass finished stratified surface and its development process using areal surface parameters, provide guidance on the optimal parameters and samplingmethod to characterise this surface type for a given application, and detail the spatial variation in surface topography due to coupon edge shadowing. Blasted and peened square plate coupons in titanium alloy arewet (vibro)massfinished iteratively with increasing duration. Measurement fields are precisely relocated between iterations byfixturing and an image superimposition alignment technique. Surface topography development is detailedwith ‘log of process duration’ plots of the ‘areal parameters for scale-limited stratified functional surfaces’, (the Sk family). Characteristic features of the Smr2 plot are seen tomap out the processing of peak, core and dale regions in turn. These surface process regions also become apparent in the ‘log of process duration’ plot for Sq, where lower core and dale regions are wellmodelled by logarithmic functions. Surface finish (Ra or Sa) withmass finishing duration is currently predictedwith an exponentialmodel. This model is shown to be limited for the current surface type at a critical range of surfacefinishes. Statistical analysis provides a group of areal parameters including; Vvc, Sq, and Sdq, showing optimal discrimination for a specific range of surfacefinish outcomes. As a consequence of edge shadowing surface segregation is suggested for characterization purposes.