•Thin polycrystalline SiC films grown by the pulsed laser deposition technique were irradiated by 800keV Ar ions at a dose of 2.6×1014at/cm2.•The SiC films hardness and Young modulus values significantly decreased after irradiation.•Glancing X-ray diffraction investigations showed a partial transformation of the SiC hexagonal phase into the cubic phase.•Smooth PLD grown thin films are excellent for radiation effects investigations using XRR, GIXRD and nanoindentation techniques. The effects of 800keV Ar ion irradiation on thin nanocrystalline SiC films grown on (100) Si substrates using the pulsed laser deposition (PLD) technique were investigated. On such PLD grown films, which were very dense, flat and smooth, X-ray reflectivity, glancing incidence X-ray diffraction and nanoindentation investigations were easily performed to evaluate changes induced by irradiation on the density, surface roughness, crystalline structure, and mechanical properties. Results indicated that the SiC films retained their crystalline nature, the cubic phase partially transforming into the hexagonal phase, which had a slightly higher lattice parameter then the as-deposited films. Simulations of X-ray reflectivity curves indicated a 3% decrease of the films density after irradiation. Nanoindentation results showed a significant decrease of the hardness and Young's modulus values with respect to those measured on as-deposited films. Raman and X-ray photoelectron spectroscopy investigations found an increase of the CC bonds and a corresponding decrease of the SiC bonds in the irradiated area, which could explain the degradation of mechanical properties.