Flow burnishing with glass microspheres and its impact on the surface condition of 2017A alloy elements

The paper describes a new finishing method - Microsphere Flow Burnishing (MFB). In terms of its kinematic properties the process is similar to Abrasive Flow Machining (AFM) except instead of abrasive grains it uses glass microspheres with a diameter less than 1 mm. This changes the nature of the process - instead of machining, it involves plastic deformation (flattening) of surface irregularity peaks, which amounts to smooth burnishing. Following a theoretical discussion, this paper determines the conditions necessary to obtain plastic deformations with minimum and maximum concentration of spheres in a semi-fluid polymer medium. Effects of burnishing, such as the following, were confirmed by means of experiments: decrease in roughness and increase in micro-hardness of the surface and compressive stresses in the outer layer. The effect of the presence of spheres in the medium, the diameter of the spheres, and pressure and velocity of the processing medium on MFB results are specified in the form of mathematical models - quadratic polynomials. It was established that without any particular difficulty it was possible to obtain a surface roughness Sa of < 0.3 mu m and its four-fold decrease as compared to the initial value. Thus, it may be concluded that MFB significantly improves the surface texture and may successfully be used for 2017A alloy finishing.