Sustainable Diamond Burnishing of Chromium–Nickel Austenitic Stainless Steels: Effects on Surface Integrity and Fatigue Limit

This study aims to evaluate the influence of lubrication and cooling conditions in the diamond burnishing (DB) process on the surface integrity and fatigue limit of chromium–nickel austenitic stainless steels (CNASSs) and, on this basis, identify a cost-effective and sustainable DB process. Evidence was presented that DB of CNASS performed without lubricating cooling liquid satisfies the requirements for a sustainable process: the three key sustainability dimensions (environmental, economic, and social) are satisfied, and the cost/quality ratio is favorable. DB was implemented with the same values of the main governing factors; however, four different lubrication and cooling conditions were applied: (1) flood lubrication (process F); (2) dry without cooling (process D); (3) dry with air cooling at a temperature of −19 °C (process A); and (4) dry with nitrogen cooling at a temperature of −31 °C (process N). Conditions A and N were realized via a device based on the principle of vortex tubes. All four DB processes provide mirror-finished surfaces with Ra roughness parameter values from 0.041 to 0.049 μm, zones with residual compressive stresses deeper than 0.5 mm, and increases in the specimens’ fatigue limit (as determined by the accelerated Locati’s method) compared to turning and polishing. Processes F and D produce the highest microhardness on the surface and at depth. The process D introduces maximum compressive residual axial and hoop stresses in the surface layer. The dry DB processes (D, A, and N) form a submicrocrystalline structure with high atomic density, which is most strongly developed under process D. When high fatigue strength is required, DB with air cooling should be chosen, as it provides a more favorable cost/quality ratio, whereas dry DB without cooling is the most suitable choice for applications that require increased wear resistance.