Investigation of anomalous strengthening on the near-surface layer of ADI at the influence of the TRIP effect by durometric methods

DOI: 10.62564/M4-AG1431

Yuriy Podrezov, Mykola Minakov, Alex Golubenko

Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine


Durometric methods have been used to study the strengthening mechanisms of the surface layer of Austempered Ductile Iron (ADI) during friction [1]. The motivation of the work is to create scientifically based approaches to optimize the composition, structure and manufacturing conditions of soil tillage machinery. ADI samples (3.44%C; 2.62%Si; 0.024%Cr; 0.54%Cu; 0.71%Ni) with different Mn contents: 0.78% and 0.24%(wt.) in both initial and deformed states was tested. The ADI structure was obtained by austenitizing heating at 900°C for 30min. followed by isothermal quenching in liquid tin at 350°C. The content of austenite and martensite in the initial and post-friction states was determined using X-ray analysis on DRON-3M. Hardness was measured using PMT-3 at a load P=0.2N. Instrumental indentation, recording the load P–indenter displacement h curve, was done using a Micron-GAMMA (P=0.2N). Pop-ins (an increase in the depth of indenter penetration without an increase in load) on the P(h) curves of ADI indicate martensitic transformations during indentation. The effect is observed at P~0.1N and h~1.5µm. Microhardness in the initial material and after friction showed that on the wear surface one third of the indents has hardness higher than the max. hardness of the initial sample (~6.5GPa) and corresponds to the hardness of martensite (7.5–9.5GPa). X-ray analysis of near-surface layers confirmed the transformation of most residual austenite into martensite. Due to martensitic transformation the average hardness after friction increases from 4.9GPa to 6.9GPa. Intensive deformation strengthening of bainitic cast iron occurs due to martensitic transformation induced by plastic deformation in the wear zone–the TRIP effect (Transformation-Induced Plasticity). The proposed research methods enable the analysis of the influence of phase composition and structural state on the effectiveness of strengthening the surface layer of ADI products under the influence of the TRIP effect.

Keywords
Instrumental indentation, Hardness, Austempered Ductile Iron, Transformation-Induced Plasticity Effect

Acknowledgments
Not provided

References
[1] Y. Podrezov, N. Minakov, B. Shurigin, A. Golubenko, K. Grinkevich, M. Askerov, K. Gogajev, Durometric analysis of hardening of the near-surface layer of ADI during friction at the influence of the TRIP effect, Uspihi materialoznavstva, 2023. No. 7. P. 37-49. (in Ukrainian)