Microstructural characterisation of borided binary Fe-W alloys

Binary Fe-W alloys with 1, 2, 4, 8, 12 and 16 at.-% W additions were prepared to investigate the effect of tungsten on the boronising behaviour by performing pack boronising at 1100 degrees C for 3 h. The borided samples were characterised using SEM, SEM-EPMA, X-ray diffraction, microhardness tester and profilometer. The formation of the FeW2B2 and FeWB precipitates in the main boride layer, the transition zone was verified, and their number and size increased in the main boride layer and transition zone with increasing amount of W in Fe-W binary alloys. The cross-sectional etching with strong acid solution and SEM examination of borided samples revealed the 3D morphology of the FeWB boride crystals with various shapes in the transition zone. The thickness of the boride layer decreased while the average microhardness values of the main boride layer and transition region increased with increasing W contents in the Fe-W binary alloys.