Formation and characterization of boride coatings thermochemically grown on the Fe64Ni36 alloy

Boride coatings were grown on Armco iron and Fe64Ni36 alloy at 850 deg. C for 20 min and 1 h, using a high boron potential powder constituted by KBF4-activated amorphous boron. The coatings were characterized by X-ray diffraction, Moessbauer spectroscopy and metallographic techniques. The use of high boron potential media allows iron borides to form with high Ni contents because of a considerable reduction of the selective reactivity of boron towards Fe and Ni. As a consequence of the isomorphism between Fe2B and Ni2B and between FeB and NiB, the high amounts of Ni in iron borides do not significantly modify the XRD patterns, while they give rise to remarkable variations in the hyperfine parameters.