Features of structure formation during liquid carburizing of AISI 321 and AISI 310S chromium-nickel austenitic steels

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Abstract

Problem. Chromium-nickel austenitic steels of the AISI 300 series are important structural materials for industrial applications over a wide range of operating temperatures. The most effective way to increase the strength, wear
resistance, and durability of products made from such steels is the creation of diffusion or cladding layers, which both
harden the steel and perform a protective function. Aim. To identify the influence of the chemical composition of AISI
310S and AISI 321 chromium-nickel austenitic steels on the features of structure formation during liquid carburizing.
Methods. The studies were carried out using optical and scanning electron microscopy, X-ray diffraction, and durometric
analysis. Results. It was found that after liquid carburizing at a temperature of 780 °C, the total content of carbide phase in
AISI 310S steel is almost four times higher than in AISI 321 steel, amounting to 39.3 and 9.3 wt.%, respectively. Differences in the type of chromium carbides precipitated during carburizing of the investigated steels were revealed (Cr23C6 in
AISI 321 steel and Cr7C3 in AISI 310S steel). It was identified that in both investigated steels, cementite Fe3C is also
formed; however, discrepancies in the position of the characteristic peaks of cementite are observed. It was shown that
the intensity of carbide formation processes during liquid carburizing of austenitic steels directly affects the depth of
the hardened layer, which amounted to about 500 μm for AISI 321 steel and about 200 μm for AISI 310S steel. It was established that carburized AISI 321 steel has a significantly higher surface hardness (890 HV0.025) compared to the surface
hardness of carburized AISI 310S steel (590 HV0.025), which is due to the presence of α-martensite in the structure of
AISI 321 steel. Conclusions. The chemical composition of austenitic AISI 310S and AISI 321 steels has a significant impact on the processes of structure formation during liquid carburizing, which is caused by different diffusion conditions.

About the authors

Roman A. Savrai

Institute of Engineering Science of the Ural Branch of RAS

Email: ras@imach.uran.ru
ORCID iD: 0000-0001-9873-3621

Doctor of Sciences (Engineering),
Head of Laboratory of Constructional Material Science 

Russian Federation, 620049, Russia, Yekaterinburg, Komsomolskaya Street, 34

Polina A. Skorynina

Institute of Engineering Science of the Ural Branch of RAS

Author for correspondence.
Email: polina.skorynina@mail.ru
ORCID iD: 0000-0002-8904-7600

PhD (Engineering), Researcher

Russian Federation, 620049, Russia, Yekaterinburg, Komsomolskaya Street, 34

Yury M. Kolobylin

Institute of Engineering Science of the Ural Branch of RAS

Email: uramk@mail.ru
ORCID iD: 0000-0002-7831-2624

Junior Researcher

Russian Federation, 620049, Russia, Yekaterinburg, Komsomolskaya Street, 34

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