Desenvolvimento de ferro nodular Si-Mo modificado ao cromo para aplicação em altas temperaturas

Abstract

Optimization the combustion processes aiming for fuel consumption reduction, the operating temperatures increases resulting on turbo compressor housing premature failure for the ordinary cast iron traditionally applied as compressor housings. The high Si-Mo ductile iron with molybdenum addition present suitable for this application, due to its low manufacturing cost and attendance of properties for high temperature application ((650 – 950ºC). The goal for the present research is to present a study intending to ferritic high Si-Mo ductile iron with chromium alloying, keeping its required properties for the proposal application aiming for competitiveness with a lower cost product. The ductile iron with silicon, molybdenum and chromium addition (C 2,84; Si 4,70; Mo 0,55; Cr 0,7) was performed to pour Y block, which were heat treated (TT1 - 940ºC / 3 h, TT2 - 920ºC / 3 h e TT3 - 920ºC / 1,5 h, followed by controlled cooling up to 750°C and subsequent furnace cooling) and characterized at room and high temperature. The microstructural characterization is performed by optical microscopy, electronic microscopy by Field Emission Gun (FEG). The mechanical characterization is performed by tensile test at room temperature and tensile test at high temperature, at 700ºC, and Brinell hardness. The as cast sample is composed by a ferritic perlitic matrix surrounded by an interconnected perlitic and carbide presence at interdentritic areas. The heat treated condition is composed by a ferritic matrix, with a low presence of perlite at the grain boundary. The mechanical room temperature properties of the heat treated condition achieved the final set properties. The mechanical high temperature properties of the heat treated condition were closely related for the three presented conditions and similar to the comparison with nearly same application materials, disclosing the potential application for the developed alloy and material alloying