•The optimal surface heating and droplet injection for wet steam have been obtained.•Kinetic energy, erosion, wetness, loss, and cost are considered objective functions.•The optimal case indicates an increase in the kinetic energy ratio by 8.68 %.•In the optimal case, erosion is reduced by 14.17 %, wetness by 2.8 %, and loss by 0.91 %. In the last stages of the steam turbine, due to the reduction in pressure, the inlet flow is accompanied by droplets. The innovation in this study pertains to determining the optimal amount of surface heating (SH) and wetness at the inlet (WAI) using the TOPSIS method for the turbine blade cascade. In this context, three conditions have been simulated: WAI (wetness at the inlet), SH (surface heating), and simultaneously with WAI and SH. The kinetic energy ratio (KER), erosion rate ratio (ERR), wetness fraction ratio (WFR), condensation loss ratio (CLR), and cost price (CP) are considered objective functions. Navier–Stokes equations coupled with nucleation and droplet growth equations are obtained together by applying SSTk−ω. Numerical method validation is conducted with Bakhtar's data. Finally, case 1-B is proposed as the optimal case. In this case, the SH is equal to 180 (kWm2) and the average wetness fraction is equal to 1 %. The comparison of the optimal case with the original case indicates that the kinetic energy ratio is increased by 8.68 %, the erosion rate ratio is reduced by 14.17 %, the wetness fraction ratio is reduced by 2.8 %, and the condensation loss ratio is decreased 0.91 %. Display omitted