Resistência à corrosão e ao desgaste de recobrimentos metálicos produzidos com ligas amorfizáveis a base de ferro
Abstract
Amorphous Iron-based alloys can be processed in such a way that, if
well designed, it can ensure an attractive combination of mechanical and
electrochemical properties, particularly in petrochemical industries where high
level of wear and corrosion resistance is required.
The success in obtaining such properties is dependent on the design
quality, which is dependent on the level of technical-scientific knowledge of the
area. Thus, in the present work, we attempted to conciliate a scientific study
and a practical application.
The work was divided into three parts, the first one is: the evaluation of
corrosion resistance of amorphous alloys in the form of ribbons prepared by
melt spinning from pure elements; the second one is: the characterization and
evaluation of electrochemical properties of amorphous ribbons made of
superduplex commercial alloy modified with boron (SDM) in front of the
crystallization level. And, in the last part, a more practical application was
developed, where in partnership with Hydro-Québec in Canada, the HVOF
thermal spray process in substrate pipes used in drilling wells by Petrobrás
Company was performed.
Powders from spray forming and high energy ball milling as ZOZ mill
type were produced, the coatings showed different levels of crystallization. In
this way it was possible to conciliate the results with those obtained from
previous steps. The characterizations were performed by several techniques
such as XRD, DSC, SEM, TEM, EDS, MO, analysis of hardness and porosity.
The corrosion resistance properties were evaluated from the polarization
curves for high salt media (35 g/L NaCl) and the coatings were evaluated by
abrasive wear tests on dry sand/rubber wheel. The results indicated a large
capacity of alloy SDM to achieve a combination of properties such as corrosion
and wear resistance.