Influence of electrolytic plasma nitriding mode on structural phase state of pearlitic steel

The paper describes results of studies of phase transitions in structural phase state occurring in the type 0.34C-1Cr-1Ni-1Mo-Fe steel under electrolytic plasma nitriding in nitrogen-containing water solution. The nitriding voltages considered in the given study were 550 and 600 V. The research was conducted by means of X-ray diffraction electron microscopy. The specimens were studied in two states : 1) before modification (original state) and 2) after nitriding in the surface layer of the specimen. The study was conducted on thin foils. It was found that nitriding lead to significant changes in the structure of steel, namely in its phase composition and in the number of existing phases. In the original state the structure of steel was given as lamellar pearlite, ferritic carbide mix and fragmented ferrite. After 550 V nitriding it was lath martensite, plates of α-phase, with colonies of thin parallel plates of γ-phase and coarse grains of α-phase, containing γ-phase grains which were different in size and shape and were various-directional. Increase in nitriding voltage up to 600 V lead to change in the structure given as a lamellar non-fragmented pearlite and fragmented ferrite. The original state was marked by presence of particles of M3C cementite, after nitriding irrespective of the voltage it had the particles of M3C alloyed cementite, Fe3Mo3N nitride and Cr2C0.61N0.39 carbonitride. The sizes, volume fractions and locations of particles were dependent on nitriding voltage.

Download Full-text

Influence of electrolytic plasma nitriding mode on structural phase state of pearlitic steel

MATEC Web of Conferences ◽

10.1051/matecconf/201714303004 ◽

2018 ◽

Vol 143 ◽

pp. 03004

Author(s):

Natalya Popova ◽

Lyudmila Erygina ◽

Elena Nikonenko ◽

Mazhin Skakov

Keyword(s):

Phase State ◽

Plasma Nitriding ◽

Structural Phase ◽

Pearlitic Steel ◽

Structural Phase State

Download Full-text

INFLUENCE OF ELECTROLYTIC PLASMA CARBONITRIDING ON STRUCTURAL PHASE STATE OF FERRITIC-PEARLITIC STEELS

Izvestiya Ferrous Metallurgy ◽

10.17073/0368-0797-2019-10-782-789 ◽

2019 ◽

Vol 62 (10) ◽

pp. 782-789 ◽

Cited By ~ 1

Author(s):

N. A. Popova ◽

E. L. Nikonenko ◽

A. V. Nikonenko ◽

V. E. Gromov ◽

O. A. Peregudov

Keyword(s):

Surface Area ◽

Phase State ◽

Lath Martensite ◽

Structural Phase ◽

Central Area ◽

Original State ◽

Volume Fractions ◽

Thin Foils ◽

Before And After ◽

Modified Layer

The change in phase composition and fine texture occurring in the ferritic-pearlitic 0.18C – 1Cr – 3Ni – 1Mo – Fe, 0.3C – 1Cr – 1Mn – 1Si – Fe and 0.34C – 1Cr – 1Ni – 1Mo – Fe steels under electrolytic plasma carbonitriding was investigated by transmission electron microscopy (TEM) method conducted on thin foils. Carbonitriding was implemented by surface saturation with nitrogen and carbon in aqueous solution under the temperature of 800 – 860 °C during 5 minutes. All steels were investigated before and after carbonitriding. It was ascertained that in the original state steel is given as a mixture of grains of pearlite and ferrite. Carbonitriding has led to creation of modified layers: the bigger was the amount of pearlite before the beginning of carbonitriding, the thicker was modified layer. Carbonitriding resulted in significant qualitative changes in phase state and structure of steel. It was revealed that in the surface area of modified layer along the matrix, there were also particles of other phases: carbides, nitrides and carbonitrides. In the course of removing from the surface of carbonitrided sample, their complete set and volume fractions decrease and at the end of modified layer only one carbide phase is present in all steels, i.e. cementite. It was found that matrix of all steels after carbonitriding is tempered packet (lath) and lamellar martensite. In the surface area of carbonitrided layer the volume fractions of lath and lamellar martensite depend on the original state of steel – the bigger was the amount of pearlite in steel the less lath martensite and the more lamellar martensite was formed. Such a dependency cannot be observed in the central area, and at the end of carbonitrided layer volume fractions of martensite packets and plates are commensurate.

Download Full-text