Glass-formation and corrosion properties of Fe-Cr-Mo-C-B glassy ribbons with low Cr content

The effect of low amounts of Cr on glass forming ability and corrosion behavior of Fe(65−x)CrxMo14C15B6 (x = 0, 2, 4, 6, 8, 10 at.%) ribbons have been studied. It was found that the reduced glass transition temperature (Trg) do not change significantly with Cr content. The glass forming ability (GFA) of this system is evaluated by the γm, δ and ω parameters and the alloys containing 4 and 6 at.% were found to be the best glass formers in this system. The temperature interval of the supercooled liquid region (ΔTx) changed with Cr and was enlarged from 35 K at x = 0 to 50 K at x = 4. Corrosion rates measured by immersion tests in H2SO4 decreased with an increase of chromium content in the alloys. The electrochemical measurements indicate that the alloys containing more than 4 at.% of Cr are spontaneously passivated with low current densities in 0.1 N H2SO4 whereas the alloys with Cr content <4 at.% showed transpassive Mo dissolution. In view of these results, the optimal amount of Cr addition in Fe-Mo-C-B amorphous steels is discussed.