High-temperature abrasive wear behaviour of strengthened iron-aluminide laser claddings

Abstract

Strengthened iron-aluminides (Fe3Al-based) show notable mechanical properties alongside good scratch hardness up to 600 °C. To investigate the influence of strengthening mechanisms for alternative high temperature wear resistant materials, laser metal deposited alloys based on Fe with 30 at.% Al were studied in detail. After cladding the Fe30Al base material and its alloys – with either 5 at.% Si, 5 at.% C or 3 at.% Ti combined with 6 at.% B – thorough investigations by scanning electron microscopy, electron backscatter diffraction, nanoindentation, hot hardness measurements, and high temperature scratch tests were performed.All alloyed Fe3Al-based claddings show increased strength. The highest overall hardness of ~405 HV10 exhibits the carbon-alloyed one containing a high fraction of Fe3AlC0.6 carbides. Contrary, the Ti + B alloyed as well as the Si-alloyed claddings are superior with their scratch hardness (especially at elevated temperatures), through the formation of TiB2 precipitates and pronounced solid solution strengthening, respectively. Wear tests reveal decreasing wear rates with increasing test temperatures (from 20 to 500 to 700 °C) for all alloyed Fe3Al-based claddings due to the formation of abrasive-containing mechanically mixed layers. Contrary, the reference cladding, cobalt-based Stellite 21 exhibits not only a higher wear rate but also increased ones upon increasing the test temperature. Detailed investigations show that the scratch hardness correlates with the wear resistance and that the incorporation of abrasive material into the wear-induced formation of mechanically mixed layers is highly beneficial. Due to this self-protection effect, the promising overall high temperature behaviour, combined with the alloying concept (no Co, Ni, or Cr), these alloyed Fe3Al-based claddings are promising candidates for sustainable wear protection outperforming currently used wear protection solutions.