APPLICATION OF MECHANICAL BARKHAUSEN NOISE IN ASSESMENT OF X20 STEEL PROPERTIES AFTER HEAT TREATMENT

Paweł Maciakowski - Bolesław Augustyniak - Marek Chmielewski - Leszek Piotrowski

   X20CrMoV12.1 steel samples after various heat treatments (austenitizing 1050°C, for 1 h and tempering 720-780°C for 15-240 min) were examined. Magnetic hysteresis loops, mechanical hardness, magnetic coercivity, magnetic and mechanical Barkhausen noise measurements were made. It was found that mechanical Barkhausen noise intensity envelopes are more sensitive to the heat treatment conditions than other classical properties. It was revealed that tempering at a temperature of 780°C for duration of more than 30 minutes is different in character than other examined heat treatment conditions. Fresh martensite may be formed in theses conditions. It is possible that the differences in magnetic and mechanical Barkhausen noise properties in the measured samples are due to higher sensitivity of non-180 degree magnetic domain walls to tempering.

Keywords: mechanical Barkhausen noise, tempering, martensitic steels, heat treatment, non-destructive testing, magnetic properties

[full-paper]