Phase selection during solidification of AISI 420 and AISI 440C tool steels

Abstract

In the present work the influence of solidification conditions on the primary solidification modes of two martensitic stainless tool steels (AISI 420 and AISI 440C) is analysed, with the aim of establishing a basis for the selection of the laser treatment parameters that lead to the most favourable microstructures. Kurz, Giovanola, and Trivedi s solidification model is used to analyse the competition between δferrite and austenite during solidification. The theoretical calculations are compared with experimental results obtained after laser surface melting of AISI420 and AISI 440C with scanning speeds from 1 × 10⁻³ to 2 × 10⁻¹ m s^−l. Calculated results are in good agreement with experimental observations and it is shown that, although the equilibrium solidification mode of both steels used is δferrite, the precipitation of primary austenite from the liquid is kinetically favoured.