Stainless steel as an antiwear material for the bio-fuel industry

Abstract

In the 1980s, Brazil started a national program to use bio-fuels as one its main energy sources, in particular ethanol produced from sugar cane. Since then, the increase of production and efficiency in the crop fields has drastically reduced the period available for the annual maintenance of the industrial plants. One of the main reasons for the annual maintenance is premature wear of devices used to wash, cut and crush sugar cane. Samples of components of such devices were collected from different sugar plants and had their wear mechanisms characterized by SEM and laser interferometry. The predominant wear mechanisms were sliding and rolling of abrasive particles and corrosion. In order to reproduce these wear mechanisms, both a lapping-like tester using large soft abrasive particles and a free ball micro-abrasion tester using fine soft abrasive particles were used. A structural carbon steel (reference material) was compared with a low alloy steel and different stainless steels, using dry and wet versions of each tester. For tests where the rolling of abrasive particles predominated, all stainless steels presented superior performance, especially under wet conditions. On the other hand, for tests with predominance of particle sliding, the low alloy steel was superior under dry conditions, but under wet conditions, with a corrosive component, stainless steels performed better. The pilot use of these laboratorial results in three industrial plants, where abrasive and corrosive conditions coexist, showed their excellent correlation with field tests. The use of stainless steel increased wear life, corroborating the importance of the synergistic effect between corrosion and abrasion. With the successful results obtained with the pilot substitution of some parts that were conventionally manufactured using carbon steel by similar parts in stainless steel, which started in 2003, this substitution increased, so that since 2007 almost all parts in the initial stages of sugar cane processing in the main Brazilian industrial plants have been manufactured using P410D stainless steel.