Efeito do teor de titânio no endurecimento por precipitação em uma liga à base de Co-Ni e consequências nas propriedades mecânicas

Abstract

The alloy subject of this study, designated by the Unified Numbering System, R30035 and internationally known as MP35N®, is a 35 Ni – 33.5 Co – 20.5 Cr – 9.5 Mo alloy with very-high mechanical strength, ductility, and corrosion resistance. Therefore, it is commonly found under extreme conditions in aerospace, medical, motorsport and petrochemical industry components. Due to this wide range of applications, there are different international standards and specifications for the alloy, which define limits on mechanical properties, or specific ranges of chemical composition for the amplification of some particular property, whether mechanical resistance or corrosion. Changes in the chemical composition have greater potential for altering the alloy's further processing. Specifically, the restrictions of the maximum titanium content in 0.1% compared to the usual 1.0%, in some applications, lead to drastic changes in the plastic behavior of the material, and, in its solidification process, observed in this work. To study the effects of this variation on the chemical composition of the alloy, on the mechanical properties, ingots were produced on a pilot scale in a VIM furnace, which were subsequently hot-formed, solubilized and cold-worked. The basic mechanical properties of the materials were evaluated through tensile, hardness and Charpy-V impact tests at room temperature, after aging in the laboratory. The main difference was the material ductility variation associated with the presence of titanium carbides.