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The article examined the effect of the type of cooling and lubrication fluid used in centrifugal shot peening (CSP) on selected properties of the surface layer and surface free energy (SFE) of centrifugal shot-peened parts. The influence of the cross feed fp on the examined quantities was also analysed. After centrifugal shot peening, regardless of the type of cooling and lubrication fluid, a point-like arrangement of micro-irregularities was obtained. The lowest surface roughness parameters Sa, Sz, Sv, Sp, and the highest material bearing ratio Smr were obtained after shot peening with oil+PMMA+MoS2. It was found that the type of cooling and lubrication fluid affected the stereometric properties of the surface layer, confirmed by statistical analysis. The use of shot peening induced changes in the surface layer’s microstructure, creating a “mosaic” structure. The treatment strengthened the surface layer, with the width of the strengthened layer being approximately 100 μm. Results showed that the cooling and lubrication fluid type had a negligible impact on the microhardness of the surface layer. Whatever the centrifugal shot peening conditions, compressive stresses occurred in the surface layer, but their values varied depending on the cooling and lubrication fluid used. After CSP, the state of free surface energy changed. It was assumed that the changes in the properties of the surface layer and SFE induced by shot peening with oil+PMMA+MoS2 were most likely due probably to the Rehbinder effect. It was found that the effect of cross feed fp had an insignificant effect on the obtained properties of the surface layer and SFE. The most favourable properties of the surface layer were obtained after centrifugal shot peening conducted with oil+PMMA+MoS2.
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