Author(s):
1. Stojana Vesković Bukudur, HIDRIA d.o.o., Slovenia
2. Milan Bizjak, University of Ljubljana, Faculty of Natural Science and Engineering, Slovenia
3. Aleš Nagode, University of Ljubljana, Faculty of Natural Science and Engineering, Slovenia
4. Janez Kovač, Instutute Josef Stefan, Slovenia
5. Stjepan Kožuh, 1University of Zagreb, Faculty of Metallurgy Sisak, Croatia
6. Blaž Karpe, University of Ljubljana, Faculty of Natural Science and Engineering, Slovenia

Abstract:
Pack aluminisation process is one of the possible production methods to improve oxidation resistance at high temperatures of various types of metallic materials. It is a chemo-thermal process where products are embedded in the powder mixture, consisting of Al powder, halide activator NH4Cl, and inert diluent Al2O3 powder, and annealed at high temperature. This exposure to high temperature causes the Al diffusion into the base material and formation of the aluminide surface layer. During the component service at elevated temperatures, the oxidation resistance is obtained due to the constant formation of an aluminium oxide film that forms on the aluminide surface layer and acts as an oxygen impermeable barrier. In the present study, FeCrAl and the NiCr heat resistant alloys in the form of 1mm thick sheet were aluminised at various process parameters. The effect of time, temperature, concentration of aluminium and halide activator in the powder mixture as well as the influence of furnace atmosphere on coating formation mechanism, mass gain and the thickness of the aluminide diffusion layer was evaluated by scanning electron microscopy, X-ray photoelectron spectroscopy and microhardness analytic techniques. Isothermal exposure tests at 1200 °C for 24h in air were conducted and compared with untreated samples for high temperature oxidation resistance estimation.

Key words:
Aluminising, heat resistant alloys, FeCrAl, NiCr, high temperature oxidation

Thematic field:
Materials Science

Date of abstract submission:
02.03.2017.

Conference:
13th International Conference on Accomplishments in Mechanical and Industrial Engineering