Effect of shot peening on electrophoretic deposition of bioactive glass coating on AISI 316L stainless steel

Bioactive glass coating of SiO2–CaO–P2O5 was synthesized and deposited on shot peened stainless steel AISI 316L substrates through electrophoretic deposition. Shot peening is known to enhance the fatigue properties of the substrate material; however, the present study aims to investigate how this prior shot peening can affect on the electrophoretic coating properties and performance. Shot peening was carried using two different sets of parameters as conventional shot peening (Almen intensity: 15A and coverage:100%), and severe shot peening (Almen intensity: 7C and coverage:1500%). The coated samples were studied regarding deposition thickness, microstructure, macrotexture and surface roughness, as well as wettability with contact angle tests. Corrosion behavior was also investigated using potentiodynamic polarization and electrochemical impedance spectroscopy in simulated body fluid solutions at 37 °C. The results confirmed that the coating thickness decreased from 55.3 μm for CNP to 27 μm and 9.5 μm for CCSP and CSSP respectively. Shot peening applied before electrophoretic deposition modulated the wettability and corrosion resistance of the coated samples through variation of roughness and the extent of grain refinement. As well as, the water contact angle of CSSP sample was equal to 15.64° which is much lower than CNP (55.3°). Also, the amount of coated samples’ corrosion rate changed by this order CCSP (1.91 × 10−2)>CNP (1.31 × 10−2)>CSSP (1.07 × 10−2). The high surface energy on shot peened samples caused the smaller BG grain size deposited on surfaces. The amount of BG grain size of each sample is as follow CNP 2.12 ± 1.6 μm, CCSP 1.34 ± 0.8 μm and CSSP 0.81 ± 0.3 μm.