Avaliação das regiões de borda superficial após processos de cortes térmicos em um aço carbono com e sem pré-tratamento nanocerâmico e revestimento e-coat acrílico

Abstract

Thermal cuts are widely used in industries in order to obtain manufactured metal parts with good surface finish and preservation of their metallurgical properties, for use in subsequent production processes. Thus, many aspects that tend to be influenced due to these thermal processes such as surface integrity, microstructure, thermally affected zone (ZTA), hardness and other properties were the object of study in this work. In addition to these factors, it is important to highlight the protection of these metallic materials against corrosive processes that tend to deteriorate them in industrial environments. Thus, the application of organic coatings for corrosion protection combined with an adequate chemical pretreatment is the most applicable, sustainable and economical alternative today, being part of the evaluations present in this work. Within this context, scanning electron microscopy analyzes with field emission (SEM / FEG) and dispersive energy spectroscopy (EDS) were carried out, in order to evaluate the condition of the edge regions of an ASTM A570 Grade 36 carbon steel after processing CO2 laser and plasma thermal systems. The chemical pre-treatment layer based on a nanoceramic product and organic coating by Acrylic E-coat technoly were also analyzed. It was observed the formation of micro cracks on the steel surface and the presence of pores in the deposition of the pre-treatment and the organic coating, in addition to the non-uniformity of the applied layer. In order to evaluate the condition of the microstructure of carbon steel after thermal processing, it was possible to observe the formation of a ZTA composed of martensitic needles of high hardness, such a property proved through the microhardness test of vickers. According to the cutting parameters used, it was not possible to observe their influence on the surface roughness of carbon steel, which remained constant both in the center of the CP's and in the edges adjacent to the thermal cuts. Through the grid adhesion test, it was possible to determine the degree of adhesion 0 to the applied coating, which implies the same good performance to the corrosion protection both in the centers and on the edges of the surface. However, in the salt spray test, it was concluded that the technology in E-coat Acrylic did not meet the specification of the technical bulletin that determined an exposure time of at least 500 hours. Blistering was also observed in the edge and center regions of the surface. The evaluations carried out in this work prove that thermal processing tends to influence the properties of carbon steel in regions with superficial edges and that failures or poor performance in the deposition of chemical pretreatment and organic coating, especially in those regions close to those of cuts can promote corrosive processes. In addition, through the evaluations made in this work, the CO2 laser presented itself as the most appropriate thermal cutting method when looking for better quality and finishing of the edge of parts that later go through subsequent assembly processes in the industries. [resumo fornecido pelo autor]