Study of austempered ductile cast iron enriched by particular ratio of nickel, molybdenum and copper

Abstract

This research paper combines investigation of mechanical properties of austempered ductile cast iron (ADI) and comparison with standard grades of steel and cast iron. Due to the special features of both materials - catsability from cast iron, and toughness from steel, ADI attracts an attention of industry and science because of economic benefits and high performance at the different application areas. Austempered ductile iron was tested on tension where unconventional behaviour was observed: with the increase of tensile strength almost to 1600 MPa the metal became less brittle. Hardness test revealed absence of linear relation between strength and hardness, different hardness values ~ 40 HRC or ~ 55 HRC can be reached with the same tensile strength 1000 - 1200 MPa. After successful tensile tests the main direction of further studies was solving relevant practical wear and fatigue problems in rail-wheel system. The complex practical studies demonstrated that ADI is consistent with heat treated steels including the rail steels: required tensile strength of rail steel ranges from 1180 MPa to 1280 MPa when rolling surface hardness is expected to be in the range of 38 HRC - 44 HRC, whereas tensile strength of ADI was higher, up to 1400 MPa, and hardness slightly higher than of steel, 50 HRC. Herewith the workability of frictional couple cast iron/steel 20MnCr5G exceeded work performance of steel/steel system by 14 %. Specific properties emerged from successful ratio of three elements Mo, Ni, and Cu, and properly chosen austenitization schedule.