Partner: Małgorzata Łazarska, M.Sc., Eng.

Kazimierz Wielki University (PL)

Recent publications
1.Łazarska M., Woźniak T.Z., Ranachowski Z., Trafarski A., Domek G., Analysis of acoustic emission signals at austempering of steels using neural networks, METALS AND MATERIALS INTERNATIONAL, ISSN: 1598-9623, DOI: 10.1007/s12540-017-6347-z, pp.1-8, 2017
Abstract:

Bearing steel 100CrMnSi6-4 and tool steel C105U were used to carry out this research with the steels being austempered to obtain a martensitic-bainitic structure. During the process quite a large number of acoustic emissions (AE) were observed. These signals were then analysed using neural networks resulting in the identification of three groups of events of: high, medium and low energy and in addition their spectral characteristics were plotted. The results were presented in the form of diagrams of AE incidence as a function of time. It was demonstrated that complex transformations of austenite into martensite and bainite occurred when austempering bearing steel at 160 °C and tool steel at 130 °C respectively. The selected temperatures of isothermal quenching of the tested steels were within the area near to MS temperature, which affected the complex course of phase transition. The high activity of AE is a typical occurrence for martensitic transformation and this is the transformation mechanism that induces the generation of AE signals of higher energy in the first stage of transition. In the second stage of transformation, the initially nucleated martensite accelerates the occurrence of the next bainitic transformation.

Keywords:

microstructure, phase transformation, dislocation, ultrasonics, alloys

Affiliations:
Łazarska M.-Kazimierz Wielki University (PL)
Woźniak T.Z.-Kazimierz Wielki University (PL)
Ranachowski Z.-IPPT PAN
Trafarski A.-other affiliation
Domek G.-Kazimierz Wielki University (PL)
2.Łazarska M., Woźniak T.Z., Ranachowski Z., Ranachowski P., Trafarski A., The application of acoustic emission and artificial neural networks in an analysis of kinetics in the phase transformation of tool steel during austempering, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.1515/amm-2017-0089, Vol.62, No.2, pp.603-609, 2017
Abstract:

During the course of the study it involved tool steel C105U was used. The steel was austempered at temperatures of 130°C, 160°C and 180°C respectively. Methods of acoustic emission (AE) were used to investigate the resulting effects associated with transformations and a large number of AE events were registered. Neural networks were applied to analyse these phenomena. In the tested signal, three groups of events were identified of: high, medium and low energy. The average spectral characteristics enabled the power of the signal spectrum to be determined. After completing the process, the results were compiled in the form of diagrams of the relationship of the AE incidence frequency as a function of time. Based on the results, it was found that in the austempering of tool steel, in the first stage of transformation midrib morphology is formed. Midrib is a twinned thin plate martensite. In the 2nd stage of transformation, the intensity of the generation of medium energy events indicates the occurrence of bainite initialised by martensite. The obtained graphic of AE characteristics of tool steel austempering allow conclusions to be drawn about the kinetics and the mechanism of this transformation.

Keywords:

carbon steel, austempering, lower bainite, acoustic emission (AE), neural networks

Affiliations:
Łazarska M.-Kazimierz Wielki University (PL)
Woźniak T.Z.-Kazimierz Wielki University (PL)
Ranachowski Z.-IPPT PAN
Ranachowski P.-IPPT PAN
Trafarski A.-other affiliation