Evaluation of Spheroidization on Erosive Wear of ASTM A106 Steel Used in Heat Exchangers

Abstract

One of the problems encountered in heat exchangers working at high temperatures is the degradation caused by erosive processes, especially in coal-fired power plants. One of the factors that contribute to the degradation of the material is the microstructural changes, like the spheroidization of the carbides. This reduces the mechanical strength of the material and consequently accelerates its wear process. The objective of this work was to evaluate the effect of spheroidization under erosive wear conditions on ASTM A106 steel. The samples were submitted to different treatment times and temperatures, aiming to generate spheroidization in the samples, later submitted to erosive wear tests. Loss of mass, microstructures and mechanical strength were evaluated from the microhardness, with the evolution of the spheroidization process. The samples with higher level of spheroidization, obtained in the temperatures of 730 ° C in times above 50 hours presented greater reduction of hardness that resulted in greater losses of mass. In general, with the increase of spheroidization, there is reduction of mechanical resistance and erosive erosion, but with a gradual reduction in wear rate. This is possibly due to the increased ductility / toughness of the matrix, which delays the process of debris formation on the ASTM A106 steel surface during the hot erosive process.