Comparative Non-Destructive Investigations of the Effects of Structural Changes After Heat Treatment of Carbon Steel Samples by Magnetic Noise and Vibration Methods

Abstract

The microstructure of some components that work for a long time at high temperatures changes, which leads to a reduction in their life cycle. Traditionally, the study of the resulting structures is carried out by mechanical tests and metallographic analysis. The application of non-destructive methods increases the possibilities to monitor the quality of the elements and to prevent destruction. The aim of the study is to detect changes in the microstructure after different heat treatment and ageing heating of materials via magnetic noise and vibration methods. To realize the goal, samples of high-quality medium carbon steel were prepared through targeted heat treatments, quenching and tempering at different temperatures, as well as ageing heating at temperatures of 700 o C for up to 16 hours by vibration and magnetic noise method. The natural frequencies and damping properties of forced longitudinal vibrations of various heat treated steel specimens were obtained and analyzed. Using magnetic noise method, the following parameters were obtained and analyzed: root mean square voltage (RMS), energy and envelope parameters of magnetic noise signals. The comparative application of several non-destructive methods increases the knowledge of methods and materials and makes it possible to establish their sensitivity in studying microstructural characteristics.