Characterisation of boride layer formed on Fe–Mo binary alloys

Abstract

The influence of molybdenum on the boronising behaviour of iron (with addition of 1, 2, 4, 8 and 16 wt-% Mo) was investigated by performing pack boronising at 1100°C for 3 h. The borided samples were characterised using SEM–EDS, EPMA, XRD, microhardness tester and profilometer. FeB and Fe₂B polyphase exists in all boronised pure Fe and Fe–Mo alloys. Mo₂FeB₂ precipitates were detected in the boride layer and transition zone. The increasing content of Mo in Fe–Mo alloys resulted in a decrease in the boride layer thickness. The average microhardness value of boride layers formed on pure Fe and Fe–16Mo alloys were measured as 1750 and 2050 HV, respectively, while approximate microhardness value of Mo₂FeB₂ precipitates was measured as 2600 HV. It was also observed that the increasing Mo content in Fe–Mo alloys resulted in an increment in the surface roughness from approximately 0.8 to 2.7 μm.

Keywords:

• Pack boriding
• Fe–Mo alloys
• Iron boride
• Mo₂FeB₂
• Microstructure
• Microhardness

Acknowledgements

The authors would like to acknowledge Ahmet Nazim and Adem Sen for their technical assistance in performing the analytical measurements. We would also like to thank Prof. Cuneyt Arslan for providing us the facilities to carry out the EPMA analysis.