Behaviour of 12% Ni steel with the change of initial precipitates

Abstract

Many changes have appeared in the field of die tool making in the recent years. New materials and machining techniques such as Laser Sintering or High Speed Machining enable toolmakers to increase their production and constantly raise the level of product quality. Maraging steels present the substantial group of relatively new ferrous alloys with some special features: excellent weldability, favourable mechanical properties and good heat resistance, long tool life and nevertheless user friendliness during the heat treatment process.Mechanical properties of maraging steels depend substantially on the characteristics of precipitated phases, which harden the martensitic structure during ageing. The type and shape of individual precipitates, their size and density affect the mechanical properties of these steels.The paper presents some mechanical and microstructural properties of 12% Ni maraging steel after precipitation annealing with laser-heat induced initial precipitates, predominantly the Ni3Mo, NiMn and Ni3Ti type. Considerable changes of initial precipitated phases were achieved with continuous and pulse type of laser-heat assisted precipitates initiation and growth. Technologic parameters for the initiation of precipitates may be reproduced with a common 10.6μm industrial CO2 laser, defocused to energy input of 17–300J/mm2 on each passage, a pulse duration from 10μs to continuous and a feed rate from 0.05 to 0.9m/min.