The effect of heat treatment of gray and nodular cast iron with ferrite matrix on mechanical properties and corrosion rate compared with medium carbon steel

摘要

In this work, the influence of heat treatment process and quenching in different quenchant media of medium carbon steel, gray and nodular cast iron with ferrite matrix on the hardness, ductility and corrosion rate of has been investigated. During this type of operations, the specimens were Austenizing at 900°C for one hour. Therefore, the specimens were quenched in different kind of oil as quenched medium (oil 20-50, oil 40, oil 90, and water as reference). The hardness, impact energy to measure the ductility, corrosion rate and microstructures were studied. From result of steel 0.47% carbon was clear increasing in hardness and decreasing in ductility with close varying values in oil quenchant kind comparing with as received specimen and water quenched one, corrosion rate decreased with heat treatment and quenching process due to formation of single face instead of double phase before heat treatment process which created galvanic cell. For gray and nodular cast iron it is noticeable that no changing in microstructure within heating for one hour at 900°C because the matrix in both cast iron types is ferrite, therefore no changing in mechanical properties under heat treatment process with time of one hour which is not sufficient to decomposition of graphite, but with comparison the hardness of gray cast iron is more than nodular one due to distribution of graphite flacks which increase the hardness and decrease the ductility as well as increasesing the corrosion rate compared with nodular cast iron. Microstructure of both types of cast iron have been studied after subjected the specimens to heat treatment at 1000°C and for 10 hours, the microstructures shown clear diffusion of some carbon in ferrite matrix around the graphite phase and under quenched some of martensite formed.