Surface phenomena during the early stages of sintering in steels modified with Fe–Mn–Si–C master alloys
Journal article, 2013

The characteristics of the metallic powder surface play a critical role in the development of strong bonds between particles during sintering, especially when introducing elements with a high affinity for oxygen. In this study, Mn and Si have been combined in a Fe–Mn–Si–C master alloy powder in order to reduce their chemical activity and prevent oxidation during the heating stage of the sintering process. However, when this master alloy powder is mixed with an iron base powder, differences in chemical activity between both components can lead to an oxygen transfer from the iron base powder to the surface of the master alloy particles. The present research is focused on studying the evolution of the master alloy particle surface during the early stages of sintering. Surface characterization by X-ray Photoelectron Spectroscopy (XPS) shows that the master alloy powder surface is mostly covered by a thin easily reducible iron oxide layer (~ 1 nm). Mn–Si particulate oxides are found as inclusions in specific areas of the surface. Evolution of oxides during sintering was studied on green compacts containing iron powder, graphite and Fe–Mn–Si–C master alloy powder that were heat treated in vacuum (10− 6 mbar) at different temperatures (from 400, 600, 800 to 1000 °C) and analyzed by means of XPS. Vacuum sintering provides the necessary conditions to remove manganese and silicon oxides from the powder surface in the range of temperatures between 600 °C and 1000 °C. When sintering in vacuum, since the gaseous products from reduction processes are continuously eliminated, oxidation of master alloy particles due to oxygen transfer through the atmosphere is minimized.

Master alloys

XPS analyses

Heterogeneous chemical activity

Fe-Mn-Si-C

Oxide evolution

Author

Raquel De Oro Calderón

Chalmers, Materials and Manufacturing Technology, Surface and Microstructure Engineering

Monica Campos Gomez

Universidad Carlos III de Madrid

Eduard Hryha

Chalmers, Materials and Manufacturing Technology, Surface and Microstructure Engineering

Jose Manuel Torralba Castello

IMDEA Software Institute

Universidad Carlos III de Madrid

Lars Nyborg

Chalmers, Materials and Manufacturing Technology, Surface and Microstructure Engineering

Materials Characterization

1044-5803 (ISSN)

Vol. 86 80-91

Subject Categories

Materials Engineering

Manufacturing, Surface and Joining Technology

Metallurgy and Metallic Materials

Areas of Advance

Production

DOI

10.1016/j.matchar.2013.07.022

More information

Latest update

3/23/2018