The elastic scattering of electrons from He，Ne and Ar atoms is investigated in the energy range of 0.1-20 eV by using the free-electron-gas exchange (HFEGE) potential and the modified semiclassical exchange (MSCE) potential with orthogonalization technique. The target electron distribution and the static potentials are calculated based on the atomic Roothaan-Hartree-Fock wavefunctions. The correlation and polarization effects are approximately represented with a parameter-free correlation-polarization potential. The accuracy of the HFEGE and MSCE potentials and the effects of the orthogonalization procedure on the finally calculated results are analysed by comparing the present results with that of the exact-exchange calculations and experiments.