Nitrogen Availability Of Nitriding Atmosphere In Controlled Gas Nitriding Processes

Michalski, Jerzy; Burdyński, K.; Wach, P.; Łataś, Z.

doi:10.1515/amm-2015-0201

Cited by 10 publications

(12 citation statements)

References 5 publications

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“…The kinetics of iron nitrides thickness growth and nitrogen concentration in the γ' and ε phases is a function of the nitriding potential [5]. A local equilibrium of concentrations, temperature-dependent, is established at the internal interphase boundaries.…”

Section: Introductionmentioning

confidence: 99%

“…When an inlet atmosphere of ammonia (NH 3 ) or ammonia diluted with predissociated ammonia (NH 3 /NH 3zd ) is used, the value of nitriding potential can be controlled by changing the inlet atmosphere flow rate or by changing the degree of dilution with predissociated ammonia. Regardless of the atmosphere used, the same value of nitriding potential corresponds to the same value of nitrogen availability [8]. In the case of a two-component inlet atmosphere of ammonia with nitrogen (NH 3 /N 2 ), the value of the nitrogen potential-similarly to as in the NH 3 atmosphere-can be controlled by changing the flow rate, in which case the nitrogen availability changes.…”

Section: Introductionmentioning

confidence: 99%

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The Stability of the Layer Nitrided in Low-Pressure Nitriding Process

2023

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The kinetics of the nitrided layer thickness growth and its structure depend on the nitrogen flux from the atmosphere to the nitrided surface. A nitrogen flux to the surface is more significant than a diffusion flux into the substrate, during forming surface iron nitrides and the internal nitriding zone. For pure iron, nitrided under low pressure, cutting off the nitriding atmosphere creates a flux from the subsurface layer of nitrides to the surface. The purpose of this paper is to determine the direction of the nitrogen flux in a similar situation for steels containing nitride-forming elements, thus answering the question of the stability of the layer nitrided under such conditions. The surface of X37CrMoV5-1 steel was nitrided under low pressure (of 24 hPa) and annealed in a vacuum or nitrogen. The microstructure, thickness of the nitride layers nitrided layers, the thickness of the internal nitriding zone, surface hardness and stresses were examined. The highest values of the nitrided layer properties were observed for the samples saturated only with nitrogen obtained from ammonia dissociation or additionally heated in nitrogen. It has been shown that using a pure vacuum during the annealing stage leads to unfavourable changes in the structure of the nitrided layer formed and, in particular, to the decomposition of the iron nitride layer formed at the saturation stage and occurrence of the tensile stresses—what excludes practical application of such layer. Ultimately, it has been shown that in the low-pressure nitriding process, the stability of the nitride layer of the nitrided surface strongly depends on the annealing atmosphere during the annealing stage, while the stability of the internal nitriding zone remains mainly at the same level.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Stability of the Layer Nitrided in Low-Pressure Nitriding Process

2023

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“…The nitriding potential was used to control the kinetics of the nitriding process. Its suitable selection was very important to control not only the growth kinetics of the diffusion zone, but also the thickness and phase composition of the iron nitride zone (compound zone) [2,3,6,15]. Phase composition of the compound zone (with iron nitrides) strongly influenced the hardness of the layer close to the surface.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Temperature Distribution during Laser Heat Treatment of Gas-Nitrided 42CrMo4 Steel on the Microstructure and Mechanical Properties

et al. 2020

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A gas-nitrided layer was produced on the toughened 42CrMo4 low-alloy steel using the changeable nitriding potential in order to limit the thickness of a brittle ε zone. The microstructure consisted of the compound ε + (ε + γ’) zone and diffusion zone (nitric sorbite with γ’ precipitates). Such a layer was subjected to laser heat treatment with or without remelting. The single laser tracks were formed using various laser beam powers (in the range of 0.234–0.624 kW) and scanning rates (in the range of 2.24–3.84 m·min−1) and the same laser beam diameter (2 mm). The microstructure of laser-modified nitrided layer usually consisted of re-melted zone (MZ) with coarse-grained nitric martensite Feα’ and possible ε precipitates, heat-affected zone (HAZ) with fine-grained nitric martensite Feα’ and γ’ precipitates and diffusion zone with nitric sorbite and γ’ precipitates. Sometimes, the compound zone was partially re-melted and an amount of iron nitrides remained in the MZ. Only one laser track was characterized by the different microstructure, consisting of the compound ε + (ε + γ’) zone, HAZ with fine-grained nitric martensite Feα’ and γ’ precipitates and diffusion zone with nitric sorbite and γ’ precipitates. This laser track was formed without visible effects of remelting. The effect of temperature distribution during laser heat treatment of gas-nitrided 42CrMo4 steel on the microstructure and mechanical properties was studied. The equations developed by Ashby and Esterling were used in order to determine the temperature distribution along the axis of each laser track. Taking into account the temperature profiles, it was possible to calculate the depths of MZ and HAZ. These predicted values were compared to those-measured based on the microstructure observations, obtaining good compatibility. The microstructure of the produced surface layers influenced the mechanical properties such as hardness and Young’s modulus. The hardness of MZ was higher than that of ε zone and lower than that of ε + γ’ zone when compared to nitrided layer. Whereas Young’s modulus of MZ was significantly higher than those characteristic of the compound zone in gas-nitrided layer (both ε and ε + γ’ zone) and similar to that of HAZ. The laser heat treatment (LHT) without remelting resulted in the similar hardness and slightly higher Young’s modulus of ε zone in comparison with the nitrided layer. Simultaneously, such a treatment of the nitrided layer did not influence the hardness and the Young’s modulus of ε + γ’ zone considerably. The hardness of HAZ was higher than that of MZ and that of the same area of diffusion zone in the nitrided layer because of the presence of fine-grained nitric martensite with γ’ precipitates after laser quenching.

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“…The results showed that by starting the second stage under the condition of a thin compound layer, a surface microstructure with a partially dissipated white layer and a thicker case depth with respect to conventional nitriding can be obtained [7]. Michalski et al [8] demonstrated that by lowering the nitrogen availability in the second stage it is possible to limit the growth kinetics of the compound layer and to maximise the growth kinetics of the diffusion zone. The self-diffusion coefficient for nitrogen in ε-Fe 2 N 1-Z is significantly larger than that for γ ′ -Fe 4 N 1−x [9]; thus, also the amount and distribution of ε and γ ′ nitrides reached after the first stage affect the diffusivity of N atoms and the following compound layer evolution.…”

Section: Introductionmentioning

confidence: 99%

“…Michalski et al. [8] demonstrated that by lowering the nitrogen availability in the second stage it is possible to limit the growth kinetics of the compound layer and to maximise the growth kinetics of the diffusion zone. The self-diffusion coefficient for nitrogen in ε -Fe 2 N 1- Z is significantly larger than that for γ ′-Fe 4 N 1− x [9]; thus, also the amount and distribution of ε and γ ′ nitrides reached after the first stage affect the diffusivity of N atoms and the following compound layer evolution.…”

Section: Introductionmentioning

confidence: 99%

Nitrocarburising of annealed and severe plastically deformed 16MnCr5 steel

Caliari

Timelli

Vanzo

2018

Surface Engineering

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The microstructure resulting from a gaseous multistage nitrocarburising treatment applied to a 16MnCr5 steel has been investigated to study the microstructural evolution during the process and the effects of severe plastic deformation. The depth of the compound layer and the porous zone has been measured by optical microscopy. The microstructure has been investigated by means of a scanning electron microscope equipped with both an electron backscatter diffraction detector, to assess the amount and the distribution of nitrogen nitrides, and an energy-dispersive X-ray microanalysis to reveal the N diffusion depth. Finally, microhardness investigations have been carried out. The results indicate that severe plastic deformation influences the microstructure of the compound layer, the N concentration trends and the hardness profiles. The effects of severe plastic deformation lead to a greater initial diffusivity of nitrogen, a subsequent premature N saturation in the diffusion zone and an increased porous/compact-layer thickness ratio.

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Nitrogen Availability Of Nitriding Atmosphere In Controlled Gas Nitriding Processes

Cited by 10 publications

References 5 publications

The Stability of the Layer Nitrided in Low-Pressure Nitriding Process

The Stability of the Layer Nitrided in Low-Pressure Nitriding Process

The Effect of Temperature Distribution during Laser Heat Treatment of Gas-Nitrided 42CrMo4 Steel on the Microstructure and Mechanical Properties

Nitrocarburising of annealed and severe plastically deformed 16MnCr5 steel

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