Abstract
Amorphous metallic alloys can be produced by rapid quenching from the metallic liquid at sufficient cooling rates to suppress the nucleation and growth of crystalline phases. The cooling rates required depend on the alloy constitution; generally the necessary values are in the order of 106 Ks-1[1]. There has been considerable interest in the manufacture of Fe-based metallic glasses because they possess attractive combinations of properties such as high hardness, good abrasive wear resistance together with enhanced corrosion resistance and good magnetic properties. However, in order to achieve these cooling rates in metallic alloy melts, samples less than 50 ƒÝm thick must be suddenly brought into good thermal contact with an efficient heat sink. Hence, these amorphous alloys are frequently produced in the form of ribbon or powder. An alternative approach consists to employ thermal spraying to deposit the alloys directly onto a substrate, in the form of a protective coating about 200 ƒÝm thick. In this study, FeSi powder was chosen as feedstock material. It is characterized by its good magntic properties [2- 7]. In order to control temperature and velocity of the in-flight particles during the coating deposition, on-line measurement of flame sprayed FeSi particles were performed with high-speed two-color pyrometer used especially for the spray forming process. In the same time, a wide band spectral pyrometer (LAND INFRARED) was used to monitor the coating surface temperature to ensure achieving good cooling rates. X-ray diffraction patterns show that the FeSi coatings structure present a crystalline phase and magnetic measurements indicate the soft ferromagnetic character of this last. Abstract only; no full-text paper available.
