Effect of Profile Corners on the Nitriding Treatment of AISI H13 Hot Extrusion Dies

Abstract

One of the utmost challenges of hot aluminum extrusion is to design the die cavities with sharp corners (used to extrude thin-walled profiles) by considering the effective nitriding surface treatment of the die bearing surface in terms of nitride layer uniformity. In the present study, various AISI H13 steel samples (having commonly used profile geometric features) are manufactured using wire electro-discharge machining (EDM) and subsequently nitrided using two-stage controlled nitriding treatment. As a special case, corner features are investigated in terms of compound and nitride layers formation using optical and scanning electron microscopes. Finite element (FE) code abaqus is used to simulate the nitriding process using mass diffusion analysis in line with experimental set up. Both experimental and numerical results are found in close agreement in terms of nitrogen concentration and corresponding microhardness profiles. Some design modifications are implemented in FE code for corner profile features for uniform nitride layer development. In view of the current results, some design guidelines are suggested for effective and uniform nitride layer formation in order to secure high quality extruded product and extended die life.