Improvement of surface properties of austempered ductile iron investment castings by thermo-chemical treatment

Aim of project
30 years since the beginning of its production, austempered ductile iron (ADI) has been well known as a reliable construction material. Tensile strength above 1700 MPa, elongation reaches 15% (in case of tensile strength more than 800 MPa), hardness up to 50 HRC, fatigue properties equal or superior to those of forged steels, other properties and manufacturing recurrence have decided that constructors at present trust ADI more and more.

In the project, a new idea has been proposed to improve surface properties of austempered ductile iron investment castings by thermo-chemical treatment added to conventional ADI heat treatment.

The aim of the investigation is to increase abrasion resistance, corrosion resistance and fatigue properties of austempered ductile iron investment castings by nitriding, carbonitriding and carbonating, added to the austenitization process of ductile iron before austempering.

expected results
It is expected that the proposed method of creating deferent microstructure in the surface layer and in the core of investment casting could influence its general properties. Additionally, this method combines two different treatment processes, which is economically significant. The project makes it possible to understand how properties of ductile iron investment casting could be created by the casting process and heat treatment. It is expected to create new research direction in duplex treatment methods in case of ADI and other cast materials.