Mass transport of W atoms and variation of stoichiometry in Al-Ni coating as a result of electron beam irradiation

Variation of the effective diffusion coefficient from 2.0 × 10−7 to 1.1 × 10−5 cm2/s is detected for the first time using back scattering (BS) of ions, scanning electron microscopy (SEM) with microanalysis (wave-length dispersive spectrometry, WDS) and nanohardness. Three stages are discovered in the motion of W ions: (i) from the coating surface to the bulk (without melting), (ii) accelerated mass transfer to the bulk with melting, and (iii) sharp decreases in the peak concentration of W ions and reversal of the direction (from the bulk to the surface).