Análise de falha de martelos oscilantes de desfibradores utilizados em usinas sucroalcooleiras
Abstract
Sugarcane mills have demanded more control of their production line,
reduced loss of raw material, and a longer period before maintenance of their
equipment, aiming to increase their profitability. The main station of this
process is the mill responsible for crushing the sugar cane. Its components
such as knives, hammers, and rollers are subject to degradation processes,
mainly wear and corrosion, decreasing production efficiency and increasing
the maintenance costs. This work aims to perform the failure analysis of
hammers coated with weld, removed from a mill shredder after use. Through
compositional characterization techniques, it was determined that the base
material is a 1030 carbon steel, and the coating is a high Cr (22,2 %wt) and C
(3,65 %wt) ferrous alloy. The coating showed greater resistance to abrasive
wear compared to the base and reference material (410 stainless steel), it has
greater hardness and hard carbides (type M7C3) that act as reinforcement and
protection elements against the removal of the soft matrix material of ferrite
and austenite by abrasive action. Despite the complexity of sugarcane juice,
composed of chlorides, sulfides, and organic acids, the cyclic polarization
curves did not show significant differences between the materials tested in this
corrosive environment. The 410 stainless steel had better performance against
corrosive effects, due to the complete dissolution of Cr in the solid solution,
which ensured the formation of a protective passive film, which, unlike the
coating, with a high content of Cr, creates carbides in excesses and interfaces
depleted in Cr, representing preferential points for corrosion. The cracks in the
coating allowed the penetration of the sugarcane juice, and subsequent
detachment of the weld by impact, exposing the base material to abrasive wear
and corrosive. Greater control during the coating preparation process and the
use of a base material with greater corrosion resistance could significantly
extend the life of the hammers.
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