Effect of alloying yttrium on corrosion–erosion behavior of 27Cr cast white iron in different corrosive slurries

Chill cast white iron alloyed with yttrium from 0 to 1.5 wt.% was investigated with regard to its resistance to corrosion–erosion in different slurries, including tap water, NaOH (pH 12), and HNO3 (pH 3) solutions, respectively, mixed with 30 wt.% silicon sand. For comparison, sand cast 27Cr white iron was also evaluated. It was demonstrated that alloying yttrium considerably improved the performance of the cast white iron, and that 1.0 wt.% yttrium was the optimum quantity, above which the benefit of yttrium decreased. In absence of yttrium addition, chill cast 27Cr white iron was more erosion resistant than the sand cast 27Cr white iron in all tested media. Corrosion test, potentiodynamic polarization test, nano-indentation and micro-indentation/scratch were also performed. Results of the study suggested that the role of yttrium was mainly attributable to its beneficial effect on the corrosion resistance of the cast iron by enhancing its surface passive film rather than the mechanical properties of the bulk material.