AMORPHOUS LAYER FORMATION ON NICKEL-ALLOY SURFACE BY INTENSE PULSED ION-BEAM IRRADIATION

The formation of an amorphous layer due to irradiation of intense puls ed ion beams (PIBs) has been studied experimentally. A mixed carbon an d fluorine PIB with energy of 180 keV, ion beam current density of 180 A/cm(2) and pulse duration of 30 ns is irradiated on a Ni65Cr15P16B4 alloy, resulting in the formation of an amorphous layer on the substra te surface to a depth of 0.66 mu m which is consistent with the therma l diffusion length. Repeated irradiations of PIB lead to the formation of an amorphous phase at depths exceeding 0.66 mu m from the surface. PIB irradiation leads to rapid heating of the substrate surface to it s boiling point (2732 degrees C), and the cooling rate from the meltin g point to the glass transition point is estimated to he 2.2 x 10(9) d egrees C/s which is larger than the critical cooling rate for amorphou s layer formation of nickel alloys.