Evaluation of dispersion hardening by various coherent nitrides in nitriding alloys based on iron, nickel, and cobalt

Петрова, Л. Г.; Chudina, O. V.

doi:10.1007/bf02468235

Cited by 4 publications

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“…The present work is a continuation of the simulation of dispersion hardening of steels and alloys by nitrides upon nitriding, which is described in [1]. Dispersion hardening of surface layers occurs due to zones of internal nitriding represented by finely dispersed nitrides of the alloying elements with a high affinity for nitrogen, which are distributed in the solid solution.…”

Section: Introductionmentioning

confidence: 99%

“…When the segregations are coherent to the matrix of the alloy, the particles under deformation are broken up by the moving dislocation in accordance with the Mott-Nabarro mechanism [2]. We have considered the hardening of steels and alloys based on Ni and Co by the Mott -Nabarro mechanism in detail in [1].…”

Section: Introductionmentioning

confidence: 99%

“…Figure 2 presents a formal comparison of the efficiencies of the hardening of Fe-, Ni-, and Co-matrices by nitride particles by the mechanisms of Orowan (for incoherent particles) and Mott -Nabarro (for coherent particles). In the latter case we considered the hardening by TiN particles, because this nitride is one of the most effective hardening phases in the studied alloys [ 1 ]. The efficiencies were compared under the condition that the hardening due to Orowan is maximum (Table 2), and the same values of Az were chosen for the cal-2 Since the mechanism concerns the motion of dislocations in a plane and the distance between the particles is also measured in a plane, the volume fraction of the particles is determined by the proportion of the area of a spherical particle in an arbitrary section to the area of the matrix enclosing one particle.…”

mentioning

confidence: 99%

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Comparison of dispersion hardening by coherent and incoherent nitrides in nitriding of alloys based on iron, nickel, and cobalt

Петрова

Chudina

2000

Met Sci Heat Treat

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Comparison of dispersion hardening by coherent and incoherent nitrides in nitriding of alloys based on iron, nickel, and cobalt

Петрова

Chudina

2000

Met Sci Heat Treat

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“…Показано [17], что в системах на основе железа с нитридообразующим элементом основным механизмом упрочнения является дисперсионное упрочнение частицами стабильных нитридов: чем выше концентрация элемента, тем больше объемная доля нитридов. Это объясняет более высокий прирост микротвердости в стали с повышенным содержанием титана.…”

Section: Estimated Annealing Time In Argon Of Nitrided Steels (100%n2...unclassified

High-techs in materials science: through-the-thickness austenitic nitriding of heat-resistant steel

Petrova

2023

Science Intensive Technologies in Mechanical Engineering

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The topicality of the research is occasioned by exaggeration of working conditions of products used at high temperatures and made of heat-resistant sheet alloys, including in particular austenitic chromium-nickel steels. When steel parts under load are operated in an oxidizing atmosphere and aggressive environments, besides resistance to electrochemical and gas corrosion, they require increased strength, hardness, and heat resistance. The increase in the characteristics of these proper-ties is achieved by three-dimensional and surface hardening techniques, which include the nitration process. The applica-tion of traditional technologies of furnace gas nitriding for chromium-nickel steels is complicated due to the problems of the low rate of the nitrogen saturation, which significantly increases the process time, and the formation of chromium nitrides, which negatively affects corrosion and heat resistance. The development of new technologies for nitrogen hardening of high-alloyed chromium-containing steels is carried out in the direction of saturation process intensification and regulation of the phase composition of the nitrided layer to minimize the formation of chromium nitrides. The article is aimed at defin-ing rational technological options and modes of gas austenitic nitriding of austenic steel, making it possible to increase strength characteristics at RT and higher temperatures without sacrificing its heat resistance. Thermodynamic modeling of the phase composition based on the CALPHAD technique shows that primary ways for minimizing the release of chromium nitrides on the nitrided surface are to increase the concentration of titanium in steel and to reduce the activity of the saturat-ing gas atmosphere, which is achieved by inert gas dilution of nitrogen. Experimental studies were carried out on sheet samples of 1.5 mm thick austenic steel of the type X18N10T with a standard (0.5%Ti) and increased (1%Ti) titane content. The experiments were carried out on a laboratory installation for high-temperature nitriding (900.1200 °); pure nitrogen and mixtures of nitrogen with argon were used as saturating media. Two-stage processes consisting of nitrogen hardening in nitrogen followed by argon afterburning were also investigated. Metallographic analysis showed that at the same nitrid-ing temperature, the amount of chromium nitrides decreases in experimental steel with an increased titanium content, and dilution of nitrogen with argon reduces the temperature of chromium nitride release. According to the study of saturation process kinetic, the time of through-the-thickness nitriding of a sheet sample under different saturation modes was deter-mined, as well as the duration of de-nitriding annealing, calculated on the basis of the known thickness of the chromium nitride zone. It was found that the dispersion hardening of the zones of internal nitriding with titanium nitrides leads to an increase in the strength characteristics of steels both at RT and higher temperatures compared to the characteristics of base steel 08X18N10T after typical heat treatment, while the greatest hardening effect is achieved due to through-the-thickness nitriding of steel with 1%Ti. Recommended options for the processes of through-the-thickness nitriding of 1.5 mm sheet of experimental steel: tn=1050 ℃, N2, 16 h; tn= 1100 ℃, 50%N2 + 50%Ar, 22 h; tn=1100 ℃, N2, 5 h + tann=1200 ℃, Ar, 9 h. The temporary passive hardness of nitrided steel at RT increases by 45...50%, and when tested at 800 ℃ - by 40... 65%, de-pending on the process mode. Through-the-thickness nitriding makes it possible to raise the working temperature of steels by 100.150 ° with the same long-term strength. The heat resistance at 900 ℃ remains at the level of non-carbonated steel after two-stage processes that ensure maximum chromium nitrides removal from the surface at the annealing stage.

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Hierarchical analysis of alloying element effects on gas nitriding rate of Fe alloys: A DFT, microkinetic and kMC study

et al. 2019

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Evaluation of dispersion hardening by various coherent nitrides in nitriding alloys based on iron, nickel, and cobalt

Cited by 4 publications

References 3 publications

Comparison of dispersion hardening by coherent and incoherent nitrides in nitriding of alloys based on iron, nickel, and cobalt

Comparison of dispersion hardening by coherent and incoherent nitrides in nitriding of alloys based on iron, nickel, and cobalt

High-techs in materials science: through-the-thickness austenitic nitriding of heat-resistant steel

Hierarchical analysis of alloying element effects on gas nitriding rate of Fe alloys: A DFT, microkinetic and kMC study

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