Análise comparativa da resistência ao desgaste abrasivo utilizando um abrasômetro de tambor de revestimentos duros depositados por soldagem e de aços Hardox®

Abstract

The wear investigation is related to the core business of industries in several segments such as mining, cement, sugar and alcohol and steel. These industries require wear resistant materials, since the equipment must withstand extremely aggressive conditions. As solutions for the abrasive wear the use of welded hard coatings and high abrasion resistance plates are highlighted. The objective of this work was to evaluate and compare the abrasive wear resistance in a drum abrasometer two hardfacing alloys, one of the Fe-C-Cr system and the other of the Fe-C-Cr-B system, welded by the SMAW process and highly abrasion resistant steel plates with four degrees of hardness, 450, 500, 550 and 600 HBW. The methodology was divided into two parts, firstly, the materials characterization was sought through chemical, microstructural and hardness analysis. The second part consists of the wear resistance comparative analysis with a drum abrasometer through weight loss using iron ore as abrasive. Regarding the characterization, the four grades of Hardox® steel presented a martensitic structure on the surface, it is possible to verify a greater martensite refinement for greater hardness degrees of the steel. The microstructure of the welded alloys showed primary, carbides or borides, of types M7C3 and M23(C,B)6 involved in a matrix composed of a eutectic constituent. Comparatively, the Fe-C-Cr-B system alloy showed a microstructure refinement and a visibly greater number of carbides formed than Fe-C-Cr system. Hardfacing alloys showed higher surface hardness values and lower wear than Hardox® steels. This result was expected since welded alloys have carbides of high hardness involved by a matrix also resistant, which could have been the differential to provide a greater abrasion resistance. Among the Hardox® steels the wear reduction with the hardness increase was verified. The alloy with boron addition, despite having higher hardness values presented higher wear than the Fe-C-Cr alloy. It is possible that due to its greater hardness associated to the fact that a portion of abrasive wear by gouging (impact) occurs, a more severe wear mechanism such as micro-cracking has been favored, promoting the greater material detachment. The ASTM A-36 samples showed greater mass loss. Therefore, it is possible to establish a ranking taking into account the abrasion resistance of each material. The results have been consistent and provide data that can lead to a better materials selection among the wear protection solutions in the industry.