Replacement of Ni by Mn in Commercial High-Ni Austenitic Cast Steels Used for High-Performance Turbocharger Housings

High-Ni austenitic cast steels were fabricated by replacing the expensive Ni content by inexpensive Mn in a commercial DIN 1.4849 steel (0.4C-2.0Mn-1.5Si-20Cr-38Ni-1.5Nb (wt pct)), and their high-temperature tensile properties were enhanced by controlling the volume fraction and distribution of carbides. The 14-pct-Ni-containing steel showed the highest total fraction and most homogeneous distribution of carbides due to the smallest cell size, which played a role in improving high-temperature properties far better than those of the DIN 1.4849 steel.