Effective surface residual stress in diamond burnishing 18/8 austenitic stainless steels

Diamond burnishing (DB) 18/8 chromium-nickel austenitic stainless steel (CNASS) introduces a two-phase (austenite and strain-induced martensite) surface-layer structure. Residual stress measurements using X-ray diffraction separately for the two phases result in different outcomes due to the difference in elastic constants. The concept of effective surface residual stress (ESRS) was introduced in this study to solve this problem. The ESRS is the sum of the measured residual stresses for the two phases, multiplied by the respective weighting factors corresponding to the percentage of content of the two phases. Thus, the inhomogeneous surface (under the phase composition criterion) is homogenized, and the ESRS is an integral characteristic of this homogenized surface. The primary objective is to establish the influence of the DB governing factors on the ESRS in diamond-burnished 18/8 CNASS. This study employs an X-ray technique, planned experiment, regression analysis, and analysis of variance. A mathematical model of the ESRS was created. The burnishing velocity has the most influence on ESRS, followed by the feed rate and burnishing force. The DB method produces two effects: mechanical and thermal. Combinations of various magnitudes of the governing factors change the ratio between these effects, leading to different magnitudes of ESRS. The feed rate affects ESRS unidirectionally (increasing the feed rate decreases ESRS) because the feed rate does not create a thermal effect. Conversely, the burnishing force and velocity influence the mechanical and thermal effects created by DB. The ESRS depends on the percentage of induced martensite to a greater extent than surface microhardness.