Cast stainless steel of the Cr-Ni duplex type is used, among others, for the cast parts of pumps and valves handling various chemically

aggressive media. Therefore, the main problem discussed in this article is the problem of abrasion wear resistance in a mixture of SiC and

water and resistance to electrochemical corrosion in a 3% NaCl- H2O solution of selected cast steel grades, i.e. typical duplex cast steel,

high silicon and manganese duplex cast steel, and Cr-Ni austenitic cast steel (type AISI 316L). The study shows that the best abrasion

wear resistance comparable to Ni-Hart cast iron was obtained in the cast duplex steel, where Ni was partially replaced with Mn and N.

This cast steel was also characterized by the highest hardness and matrix microhardness among all the tested cast steel grades. The best

resistance to electrochemical corrosion in 3% NaCl- H2O solution showed the cast duplex steel with high content of Cr, Mo and N. The

addition of Ni plays rather insignificant role in the improvement of corrosion resistance of the materials tested.

Abstract An attempt has been made to determine the effect of an addition of colloidal suspensions of the nanoparticles of magnesium oxide on the structure of water glass, which is a binder for moulding and core sands. Nanoparticles of magnesium oxide MgO in propanol and ethanol were introduced in the same mass content (5wt.%) and structural changes were determined by measurement of the FT-IR absorption spectra.