Effect of Liquid Salt Bath Nitrocarburizing on Mechanical Properties of Low-Alloy Sintered Steels
The purpose of this study is to produce Fe–2Cu–2Ni–0.7Mo–XC steels by means of the powder metallurgy at different sintering temperatures. The mechanical properties of sintered steels have recently reached a level equivalent to that of steels produced by other processes. The static and dynamic mechan...
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Інститут металофізики ім. Г.В. Курдюмова НАН України
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| Cite this: | Effect of Liquid Salt Bath Nitrocarburizing on Mechanical Properties of Low-Alloy Sintered Steels / S. Serrai, S. Mechachti, O. Benchiheub, S. Boudebane, M. Fellah, M.Z. Touhami // Металлофизика и новейшие технологии. — 2018. — Т. 40, № 4. — С. 515-527. — Бібліогр.: 32 назв. — англ. |
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Serrai, S. Mechachti, S. Benchiheub, O. Boudebane, S. Fellah, M. Touhami, M.Z. 2019-02-03T15:21:21Z 2019-02-03T15:21:21Z 2018 Effect of Liquid Salt Bath Nitrocarburizing on Mechanical Properties of Low-Alloy Sintered Steels / S. Serrai, S. Mechachti, O. Benchiheub, S. Boudebane, M. Fellah, M.Z. Touhami // Металлофизика и новейшие технологии. — 2018. — Т. 40, № 4. — С. 515-527. — Бібліогр.: 32 назв. — англ. 1024-1809 PACS: 06.60.Vz, 61.72.Ff, 62.20.Qp, 81.20.Ev, 81.40.Np, 81.40.Pq, 81.65.Lp DOI: https://doi.org/10.15407/mfint.40.04.0515 https://nasplib.isofts.kiev.ua/handle/123456789/145945 The purpose of this study is to produce Fe–2Cu–2Ni–0.7Mo–XC steels by means of the powder metallurgy at different sintering temperatures. The mechanical properties of sintered steels have recently reached a level equivalent to that of steels produced by other processes. The static and dynamic mechanical properties of parts made of sintered steel depend on density and microstructure. Many process parameters such as initial composition, alloying elements, atmosphere, time, sintering temperature, and nitrocarburizing influence the microstructure of steel parts. The compacts’ preparation involves powder mixing, cold pressing at 500 MPa, and sintering at 1250°C within the H2 atmosphere for 2 hours and 25 min. The influence of sintering temperature on both hardness and microstructure of the steel is investigated. In this study, sintered Fe–2Cu–2Ni–0.7Mo–XC-type steels are developed. The impact of nitrocarburizing on this structure is evaluated. Microscopy, SEM, and destructive testing are used for characterization of the sintered steels. Метою даної роботи є одержання сталей типу Fe–2Cu–2Ni–0,7Mo–XC методами порошкової металурґії за різних температур спікання. Механічні властивості спечених сталей нещодавно сягнули рівня, аналогічного рівню сталей, що виробляються іншими методами. Статичні та динамічні механічні властивості деталів із спеченої сталі визначаються густиною та мікроструктурою. При цьому велика кількість характеристик процесу, наприклад, вихідний склад, леґувальні елементи, атмосфера, час, температура спікання та нітроцементація впливають на мікроструктуру сталевих деталів. Виготовлення пресованого матеріялу потребує змішування порошку, холодного пресування при 500 МПа та спікання при температурі у 1250°C в атмосфері Н22 протягом 2 годин 25 хв. Було досліджено вплив температури спікання на твердість і мікроструктуру сталі. В даній роботі було розглянуто сталі типу Fe–2Cu–2Ni–0,7Mo–XC. Було проведено оцінку впливу нітроцементації на такі структури. Для характеризації спечених сталей використовувалися мікроскопія, СЕМ та випробування на руйнування. Целью данной работы является получение сталей типа Fe–2Cu–2Ni–0,7Mo–XC методами порошковой металлургии при различных температурах спекания. Механические свойства спечённых сталей недавно достигли уровня, аналогичного уровню сталей, производимых другими методами. Статические и динамические механические свойства деталей из спечённой стали определяются плотностью и микроструктурой. При этом большое количество характеристик процесса, например, исходный состав, легирующие элементы, атмосфера, время, температура спекания и нитроцементация, влияют на микроструктуру стальных деталей. Изготовление прессованного материала требует смешивания порошка, холодного прессования при 500 МПа и спекания при температуре 1250°C в атмосфере Н22 в течение 2 часов 25 мин. Было исследовано влияние температуры спекания на твёрдость и микроструктуру стали. В данной работе были рассмотрены стали типа Fe–2Cu–2Ni–0,7Mo–XC. Была проведена оценка влияния нитроцементации на такие структуры. Для характеризации спечённых сталей использовались микроскопия, СЭМ и испытания на разрушение. en Інститут металофізики ім. Г.В. Курдюмова НАН України Металлофизика и новейшие технологии Физика прочности и пластичности Effect of Liquid Salt Bath Nitrocarburizing on Mechanical Properties of Low-Alloy Sintered Steels Вплив нітрокарбонізації в рідкій соляній ванні на механічні властивості слаболеґованих спечених сталей Влияние нитрокарбонизации в жидкой соляной ванне на механические свойства слаболегированных спечённых сталей Article published earlier |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
Effect of Liquid Salt Bath Nitrocarburizing on Mechanical Properties of Low-Alloy Sintered Steels |
| spellingShingle |
Effect of Liquid Salt Bath Nitrocarburizing on Mechanical Properties of Low-Alloy Sintered Steels Serrai, S. Mechachti, S. Benchiheub, O. Boudebane, S. Fellah, M. Touhami, M.Z. Физика прочности и пластичности |
| title_short |
Effect of Liquid Salt Bath Nitrocarburizing on Mechanical Properties of Low-Alloy Sintered Steels |
| title_full |
Effect of Liquid Salt Bath Nitrocarburizing on Mechanical Properties of Low-Alloy Sintered Steels |
| title_fullStr |
Effect of Liquid Salt Bath Nitrocarburizing on Mechanical Properties of Low-Alloy Sintered Steels |
| title_full_unstemmed |
Effect of Liquid Salt Bath Nitrocarburizing on Mechanical Properties of Low-Alloy Sintered Steels |
| title_sort |
effect of liquid salt bath nitrocarburizing on mechanical properties of low-alloy sintered steels |
| author |
Serrai, S. Mechachti, S. Benchiheub, O. Boudebane, S. Fellah, M. Touhami, M.Z. |
| author_facet |
Serrai, S. Mechachti, S. Benchiheub, O. Boudebane, S. Fellah, M. Touhami, M.Z. |
| topic |
Физика прочности и пластичности |
| topic_facet |
Физика прочности и пластичности |
| publishDate |
2018 |
| language |
English |
| container_title |
Металлофизика и новейшие технологии |
| publisher |
Інститут металофізики ім. Г.В. Курдюмова НАН України |
| format |
Article |
| title_alt |
Вплив нітрокарбонізації в рідкій соляній ванні на механічні властивості слаболеґованих спечених сталей Влияние нитрокарбонизации в жидкой соляной ванне на механические свойства слаболегированных спечённых сталей |
| description |
The purpose of this study is to produce Fe–2Cu–2Ni–0.7Mo–XC steels by means of the powder metallurgy at different sintering temperatures. The mechanical properties of sintered steels have recently reached a level equivalent to that of steels produced by other processes. The static and dynamic mechanical properties of parts made of sintered steel depend on density and microstructure. Many process parameters such as initial composition, alloying elements, atmosphere, time, sintering temperature, and nitrocarburizing influence the microstructure of steel parts. The compacts’ preparation involves powder mixing, cold pressing at 500 MPa, and sintering at 1250°C within the H2 atmosphere for 2 hours and 25 min. The influence of sintering temperature on both hardness and microstructure of the steel is investigated. In this study, sintered Fe–2Cu–2Ni–0.7Mo–XC-type steels are developed. The impact of nitrocarburizing on this structure is evaluated. Microscopy, SEM, and destructive testing are used for characterization of the sintered steels.
Метою даної роботи є одержання сталей типу Fe–2Cu–2Ni–0,7Mo–XC методами порошкової металурґії за різних температур спікання. Механічні властивості спечених сталей нещодавно сягнули рівня, аналогічного рівню сталей, що виробляються іншими методами. Статичні та динамічні механічні властивості деталів із спеченої сталі визначаються густиною та мікроструктурою. При цьому велика кількість характеристик процесу, наприклад, вихідний склад, леґувальні елементи, атмосфера, час, температура спікання та нітроцементація впливають на мікроструктуру сталевих деталів. Виготовлення пресованого матеріялу потребує змішування порошку, холодного пресування при 500 МПа та спікання при температурі у 1250°C в атмосфері Н22 протягом 2 годин 25 хв. Було досліджено вплив температури спікання на твердість і мікроструктуру сталі. В даній роботі було розглянуто сталі типу Fe–2Cu–2Ni–0,7Mo–XC. Було проведено оцінку впливу нітроцементації на такі структури. Для характеризації спечених сталей використовувалися мікроскопія, СЕМ та випробування на руйнування.
Целью данной работы является получение сталей типа Fe–2Cu–2Ni–0,7Mo–XC методами порошковой металлургии при различных температурах спекания. Механические свойства спечённых сталей недавно достигли уровня, аналогичного уровню сталей, производимых другими методами. Статические и динамические механические свойства деталей из спечённой стали определяются плотностью и микроструктурой. При этом большое количество характеристик процесса, например, исходный состав, легирующие элементы, атмосфера, время, температура спекания и нитроцементация, влияют на микроструктуру стальных деталей. Изготовление прессованного материала требует смешивания порошка, холодного прессования при 500 МПа и спекания при температуре 1250°C в атмосфере Н22 в течение 2 часов 25 мин. Было исследовано влияние температуры спекания на твёрдость и микроструктуру стали. В данной работе были рассмотрены стали типа Fe–2Cu–2Ni–0,7Mo–XC. Была проведена оценка влияния нитроцементации на такие структуры. Для характеризации спечённых сталей использовались микроскопия, СЭМ и испытания на разрушение.
|
| issn |
1024-1809 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/145945 |
| citation_txt |
Effect of Liquid Salt Bath Nitrocarburizing on Mechanical Properties of Low-Alloy Sintered Steels / S. Serrai, S. Mechachti, O. Benchiheub, S. Boudebane, M. Fellah, M.Z. Touhami // Металлофизика и новейшие технологии. — 2018. — Т. 40, № 4. — С. 515-527. — Бібліогр.: 32 назв. — англ. |
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515
ФИЗИКА ПРОЧНОСТИ И ПЛАСТИЧНОСТИ
PACS numbers: 06.60.Vz, 61.72.Ff, 62.20.Qp, 81.20.Ev, 81.40.Np, 81.40.Pq, 81.65.Lp
Effect of Liquid Salt Bath Nitrocarburizing on Mechanical
Properties of Low-Alloy Sintered Steels
S. Serrai, S. Mechachti, O. Benchiheub, S. Boudebane*, M. Fellah**,
and M. Z. Touhami
Badji Mokhtar University,
Laboratory of Research in Foundry,
Department of Metallurgy and Materials Engineering,
BO 12, CP 23000 Annaba, Algeria
*Badji Mokhtar University,
Laboratory of Metallurgy and Material Engineering,
BO 12, CP 23000 Annaba, Algeria
**Badji Mokhtar University,
Tribology, Materials Surface and Interfaces Group, Laboratory of Foundry,
BO 12, CP 23000 Annaba, Algeria
The purpose of this study is to produce Fe–2Cu–2Ni–0.7Mo–XC steels by
means of the powder metallurgy at different sintering temperatures. The me-
chanical properties of sintered steels have recently reached a level equivalent
to that of steels produced by other processes. The static and dynamic mechani-
cal properties of parts made of sintered steel depend on density and micro-
structure. Many process parameters such as initial composition, alloying ele-
ments, atmosphere, time, sintering temperature, and nitrocarburizing influ-
ence the microstructure of steel parts. The compacts’ preparation involves
powder mixing, cold pressing at 500 MPa, and sintering at 1250 C within the
H2 atmosphere for 2 hours and 25 min. The influence of sintering temperature
on both hardness and microstructure of the steel is investigated. In this study,
sintered Fe–2Cu–2Ni–0.7Mo–XC-type steels are developed. The impact of
nitrocarburizing on this structure is evaluated. Microscopy, SEM, and de-
structive testing are used for characterization of the sintered steels.
Corresponding author: Salim Serrai
E-mail: salimredha_206@yahoo.fr
Citation: S. Serrai, S. Mechachti, O. Benchiheub, S. Boudebane, M. Fellah, and
M. Z. Touhami, Effect of Liquid Salt Bath Nitrocarburizing on Mechanical Properties
of Low-Alloy Sintered Steels, Metallofiz. Noveishie Tekhnol., 40, No. 4: 515–527
(2018), DOI: 10.15407/mfint.40.04.0515.
Ìåòàëëîôèç. íîâåéøèå òåõíîë. / Metallofiz. Noveishie Tekhnol.
2018, т. 40, № 4, сс. 515–527 / DOI: 10.15407/mfint.40.04.0515
Îòòèñêè äîñòóïíû íåïîñðåäñòâåííî îò èçäàòåëÿ
Ôîòîêîïèðîâàíèå ðàçðåøåíî òîëüêî
â ñîîòâåòñòâèè ñ ëèöåíçèåé
2018 ÈÌÔ (Èíñòèòóò ìåòàëëîôèçèêè
èì. Ã. Â. Êóðäþìîâà ÍÀÍ Óêðàèíû)
Íàïå÷àòàíî â Óêðàèíå.
https://doi.org/10.15407/mfint.40.04.0515
https://doi.org/10.15407/mfint.40.04.0515
516 S. SERRAI, S. MECHACHTI, O. BENCHIHEUB et al.
Key words: microstructure, nitrocarburizing, alloying elements, porosity,
density, microhardness.
Метою даної роботи є одержання сталей типу Fe–2Cu–2Ni–0,7Mo–XC ме-
тодами порошкової металурґії за різних температур спікання. Механічні
властивості спечених сталей нещодавно сягнули рівня, аналогічного рів-
ню сталей, що виробляються іншими методами. Статичні та динамічні
механічні властивості деталів із спеченої сталі визначаються густиною та
мікроструктурою. При цьому велика кількість характеристик процесу,
наприклад, вихідний склад, леґувальні елементи, атмосфера, час, темпе-
ратура спікання та нітроцементація впливають на мікроструктуру стале-
вих деталів. Виготовлення пресованого матеріялу потребує змішування
порошку, холодного пресування при 500 МПа та спікання при температу-
рі у 1250 C в атмосфері Н2 протягом 2 годин 25 хв. Було досліджено вплив
температури спікання на твердість і мікроструктуру сталі. В даній роботі
було розглянуто сталі типу Fe–2Cu–2Ni–0,7Mo–XC. Було проведено оці-
нку впливу нітроцементації на такі структури. Для характеризації спече-
них сталей використовувалися мікроскопія, СЕМ та випробування на
руйнування.
Ключові слова: мікроструктура, нітроцементація, леґувальні елементи,
пористість, густина, мікротвердість.
Целью данной работы является получение сталей типа Fe–2Cu–2Ni–
0,7Mo–XC методами порошковой металлургии при различных темпера-
турах спекания. Механические свойства спечённых сталей недавно до-
стигли уровня, аналогичного уровню сталей, производимых другими ме-
тодами. Статические и динамические механические свойства деталей из
спечённой стали определяются плотностью и микроструктурой. При этом
большое количество характеристик процесса, например, исходный со-
став, легирующие элементы, атмосфера, время, температура спекания и
нитроцементация, влияют на микроструктуру стальных деталей. Изго-
товление прессованного материала требует смешивания порошка, холод-
ного прессования при 500 МПа и спекания при температуре 1250 C в ат-
мосфере Н2 в течение 2 часов 25 мин. Было исследовано влияние темпера-
туры спекания на твёрдость и микроструктуру стали. В данной работе бы-
ли рассмотрены стали типа Fe–2Cu–2Ni–0,7Mo–XC. Была проведена
оценка влияния нитроцементации на такие структуры. Для характериза-
ции спечённых сталей использовались микроскопия, СЭМ и испытания
на разрушение.
Ключевые слова: микроструктура, нитроцементация, легирующие эле-
менты, пористость, плотность, микротвёрдость.
(Received December 28, 2017)
1. INTRODUCTION
Powder metallurgy (PM) production method of steel parts with com-
plex shape is cheaper comparing to other manufacturing methods [1].
EFFECT OF NITROCARBURIZING ON MECHANICAL PROPERTIES OF STEELS 517
PM has advanced significantly over the past 30 years as a cost effective
and efficient processing technique to produce near net shape parts [2].
PM is often used when it comes to developing materials, which are not
easily developed by conventional melting processes. Metal matrix
composites reinforced by dispersing various reinforcements (carbides,
oxides, nitrides, intermetallics) are one such class of materials, which
are developed by powder metallurgy.
New powder metallurgy materials having high performance have
been required due to necessity in various industrial applications. There
are many ways to increase the performance of materials including new
alloy systems, increasing the density by using new compaction tech-
niques, increasing sintering temperature, and heat treatments. Pre-
alloyed diffusion powders have been developed in order to obtain high-
performance materials [3–5].
Many performance-enhancing pre-alloying elements such as molyb-
denum, manganese, nickel, and chromium have been used. The low-alloy
sintered Fe–Ni–Cu–Mo–C steel has a great attention of several re-
searchers [4, 6–10]. With the introduction of graphite into the iron
powder, it is possible to obtain ferrous sintered materials having differ-
ent structures and properties. Moreover, it improves the sintering be-
haviour, and a high content of graphite leads to a better dissemination.
Nickel is one of the most important alloying elements in steels, and
it can be used in ferrous alloys in low-alloy powders [11–14]. Addition
of 0.5 to 5% of nickel increases tensile strength and ductility, whereas
adding molybdenum produces a finer structure and improves its per-
formance and mechanical properties [11–14].
To be considered for high-performance applications, powder metal-
lurgy materials must have a reduced porosity and an enhanced density.
To achieve this one, various techniques have been used during the pro-
duction process of these materials. Employing high sintering tempera-
ture is an alternative way to produce PM materials with desired micro-
structural and mechanical properties.
The success of manufacturing techniques associated with powder
metallurgy undoubtedly lies in the productivity rates, which can never
be matched especially for shaping metal parts with complex geome-
tries. For some categories of parts, powder metallurgy stands as a qual-
ity alternative to the more conventional methods such as casting, forg-
ing, and machining. Powder metallurgy enables substantial savings by
eliminating rework machining.
2. EXPERIMENTAL DETAILS
Table 1 shows the chemical composition, particle size, and properties
of hydrogen-reduced iron of the two mixtures used in this study, mix-
ture 1 (2% Cu, 2% Ni, 0.7% Mo, and 0.4% C) and mixture 2 (2% Cu,
518 S. SERRAI, S. MECHACHTI, O. BENCHIHEUB et al.
2% Ni, 0.7% Mo, and 0.6% C). These mixtures are then mixed with
the starting iron powder. The powder elements origins and sizes are as
follows: reduced iron (50 m), nickel carbonyl (10 m), reduced copper
( 90 m), reduced molybdenum ( 2.61 m) and graphite (1–2 m).
In order to achieve a homogeneous mixture of powders of Fe, C, Cu,
Ni, and Mo, we used a ball mill for 10 hours. A synthetic wax was then
added at 100 ml/kg of powder to act as a lubricant during the compact-
ing operation and to increase the green density thus improving the re-
sistance of the parts after compaction and facilitating their handling
prior to sintering [15]. Then, the mixture thereof is heated in an oven
at a temperature of about 300 C.
The lubricant added to the load reduces friction couples (parti-
cle/particle) and (particle/wall) during compression, thus ensuring the
better transmission of stresses within the volume occupied by the pow-
der, which reduces density differences in the obtained agglomerates.
The samples are compacted by a 1000 kN nominal pressure hydraulic
press with axial compression.
For characterization, the sintered alloy steel samples were compact-
ed under a pressure of 500 MPa. Mechanical tests were carried out us-
ing ISO standard specimens. Their dimensions were 90 18 5 mm3
for
traction [16], 55 10 10 mm3
for resilience [17], and 30 5 5 mm3
for
flexion [18].
After preliminary testing, we opted for sintering at high tempera-
ture (1250 C for 2 hours 25 min) in a hydrogen-reducing atmosphere in
order to remove the oxides present on the grain surface and its protec-
tion from subsequent oxidation during sintering and cooling.
Liquid nitrocarburizing treatment process was performed at 580 C
for 3 hours in an industrial molten salt bath consisting of 60% KCN,
TABLE 1. Chemical composition and properties of the reduced iron powder.
Chemical composition (mass fraction), %
C 0.04
O 0.4
Fe Balance
Theoretical density, g/cm3 7.84
Bulk density, g/cm3 1.73
Size distribution of particles, %
45 59.40
45–106 39.30
106–150 1.30
150 0.5
EFFECT OF NITROCARBURIZING ON MECHANICAL PROPERTIES OF STEELS 519
24% KCl and 16% K2CO3 by weight.
3. RESULTS AND DISCUSSION
3.1. Chemical Composition and Densities of Low-Alloy Sintered Steels
The green and sintered densities were deduced from the volume and
weight measurement of the samples before and after sintering. The re-
sulting densities are shown in Table 2.
The results obtained by x-ray fluorescence analysis are given in Ta-
ble 3.
Under standard sintering conditions of low-alloy steels at a temper-
ature of 1120 C for 30 min, the diffusion, which generally occurs in a
solid state, does not allow complete homogenization of the alloying el-
ements [19]. In our case, sintering was achieved at 1250 C during 2
hours 25 min. This allowed the carbon to diffuse completely with a
homogeneous dispersion across the part.
3.2. Mechanical Properties of the Sintered and Nitrocarburized Steels
The increase in carbon content from 0.4 to 0.6% improves the tensile
strength (Rm) of the sintered steel from 215 to 256 MPa and decreases
the elongation from 0.9 to 0.6%. This is due to the formation of pearl-
ite rather than ferrite [20]. This improvement was also noticed when
the steels were treated in a salt bath. The tensile strength increases
from 235 to 270 MPa, whereas the elongation decreases from 0.5 to
0.2%. This is due to the formation of nitrocarburized surface layers
(Fig. 1), the latter tending to harden the steels (Table 4). This is also
TABLE 3. Fluorescence X chemical composition of Fe2Cu2Ni0.7MoXC sin-
tered steel samples.
Steels
Chemical Elements, %
C Ni Cu Mo Si Mn P V S
Fe0.4C2Cu2Ni0.7Mo 0.4 1.985 1.852 0.742 0.928 0.159 0.012 0.018 –
Fe0.6C2Cu2Ni0.7Mo 0.6 1.973 1.310 0.710 1.063 0.125 0.029 0.017 0.0023
TABLE 2. Green and sintered densities.
Steels Green density, g/cm3 Sintered density, g/cm3
Fe0.4C2Cu2Ni0.7Mo 6.55 6.7
Fe0.6C2Cu2Ni0.7Mo 6.67 6.8
520 S. SERRAI, S. MECHACHTI, O. BENCHIHEUB et al.
confirmed by scanning electronic microscopy (Fig. 2).
The resilience, the resistance to flexion and the Vickers hardness of
the steels were improved significantly with increasing carbon content
in both sintered and nitrocarburized states. For the sintered state,
they increase from 20.43 to 23.35 kJ/m3, 898 to 1279 N/mm2
and 235
to 239 HV, respectively. As shown in Table 4, for the treated steels,
they increase from 43 to 47 kJ/m3, 1046 to 1410 N/mm2
and 245 to
247 HV, respectively. This is due to modification of the surface layer
after nitrocarburizing. The latter promotes the formation of iron ni-
trides, which increase the hardness [21].
Copper promotes diffusion and improves quality of sintering bridg-
es [22–24], thus improving hardness and increasing steel strength
from 215 to 256 MPa (Table 4).
Figure 3 shows the evolution of microhardness depending on nitrid-
ing depth obtained for the two sintered and nitrocarburized steels,
Fe0.4C2Cu2Ni0.7Mo and Fe0.6C2Cu2Ni0.7Mo. It shows an increase in
TABLE 4. Mechanical properties of sintered and nitrocarburized steels.
Steels
Rm,
MPa
A, %
Resilience,
kJ/m3
Flexion,
N/mm2
Vickers hard-
ness, HV0.2
Fe0.4C2Cu2Ni0.7Mo
sintered
215 0.9 20.43 898 235
Fe0.6C2Cu2Ni0.7Mo
sintered
256 0.6 23.35 1279 239
Fe0.4C2Cu2Ni0.7Mo
nitrocarburized
235 0.5 43 1046 245
Fe0.6C2Cu2Ni0.7Mo
nitrocarburized
270 0.2 47 1410 247
a b
Fig. 1. Microstructures of nitrocarburized steels (3 hours) etched with 2%
Nital: Fe0.4C2Cu2Ni0.7Mo (a), Fe0.6C2Cu2Ni0.7Mo (b).
EFFECT OF NITROCARBURIZING ON MECHANICAL PROPERTIES OF STEELS 521
the microhardness of the nitrocarburized steel at the combination lay-
er (Fig. 1).
This happens due to the changes in the formed phases (precipitated
nitrides or carbonitrides), which are induced by the diffusion reactions
of the liquid bath elements (C, N) [25].
3.3. Microstructure of Sintered and Nitrocarburized Steels
Figure 4 shows the results of the metallographic analysis of samples
with varying compositions and in various states. The presence of pores
Fig. 3. Vickers microhardness profile from the surface to the centre of the sin-
tered and the nitrocarburized steel samples.
Fig. 2. SEM image of the nitrocarburized steel Fe0.4C2Cu2Ni0.7Mo.
522 S. SERRAI, S. MECHACHTI, O. BENCHIHEUB et al.
is observed in the structure of the non-etched sample (Fig. 4, a). The
enclosed pores and their spheroidization result from the progress of
sintering mechanisms with a decrease of the pore volume due to the
formation of phases such as ferrite, pearlite and soft areas of nickel-
rich austenite (Fig. 4, b) [26]. The clear appearance of the grain bound-
aries was also observed for the entire microstructure (Fig. 4, c).
Figure 5 shows that the microstructures of the sintered steel
Fe0.6C2Cu2Ni0.7Mo consist of pearlite, ferrite, and nickel rich aus-
tenitic ductile areas, mainly localized around the initial particles of
iron powders.
3.4. X-Ray Analysis Patterns of the Nitrocarburized Layers
X-ray diffraction patterns of samples (Fig. 6) show the presence of ox-
ides (Fe2O3, Fe3O4), cementite Fe3C, and iron nitrides -Fe2–3N and -
Fe4N. Iron oxides formed at the surface layer of the samples are a con-
sequence of blowing oxygen in the salt bath in order to homogenize the
composition and accelerate the diffusion process [27, 28]. Blowing ox-
ygen in the salt bath is carried out periodically during the treatment.
This affects the kinetics of nitriding and the composition of phases of
unstable ( -Fe2–3N) and stable nitride ( -Fe4N) [29]. The percentage of
the two nitrides and in the surface layer depends on the steel car-
bon content. High carbon content helps the formation of iron nitride -
Fe2–3N, and inversely, lower carbon content results in the appearance
of -Fe4N iron nitride known for its stability.
3.5. Friction Coefficient and Wear Behaviour of Sintered
and Nitrocarburized Steels
The tribological behaviour of the studied materials depends on the sin-
a b
Fig. 4. Microstructures of the sintered steel Fe0.4C2Cu2Ni0.7Mo: non-etched
(a), etched with 2% Nital (b), etched with 3% Nital (c).
EFFECT OF NITROCARBURIZING ON MECHANICAL PROPERTIES OF STEELS 523
tered steels state and on the parameters of the applied thermochemical
treatment [30]. Figure 7 shows the curves illustrating the evolution of
the coefficient of friction over a distance of 20 m for several states.
Samples sintered at 1250 C for 2 hours 25 min exhibit a similar behav-
iour during the first stage from 0 to 10 m, considered as a lapping step,
which is characterized by a sudden increase in Cf from 0.3 to 0.55–0.65
due to crushing of surface asperities. Beyond 10 m, the surface strain
hardens resulting in a stabilization of the coefficient of friction. The Cf
stabilizes at 0.5 for the Fe0.4C2Cu2Ni0.7Mo sample and at 0.6 for the
sample containing 0.6% C. This is explained by an increased content of
free graphite in the structure; and it is known that graphitization is
accelerated by the presence of elements such as Ni and Cu [31]. These
elements, by their action on the thermodynamic carbon activity, pro-
mote graphitization thus creating graphite nodules, which act as lub-
ricant. On the other hand, disturbances recorded on the curves of the
sintered Fe0.4C2Cu2Ni0.7Mo and Fe0.6C2Cu2Ni0.7Mo samples con-
firm the existence on the surface of the p-hardening-fragile fracture
cycle.
The impact of the liquid nitrocarburizing on the sintered surface
clearly appears through the values of Cf (Fig. 7, a). Low at the begin-
a b
c
Fig. 5. Microstructures of the sintered steel Fe0.6C2Cu2Ni0.7Mo: non-etched
(a), etched with 2% Nital (b), etched with 3% Nital (c).
524 S. SERRAI, S. MECHACHTI, O. BENCHIHEUB et al.
ning of the test (0–5 m), the coefficient of friction of the
Fe0.4C2Cu2Ni0.7Mo and Fe0.6C2Cu2Ni0.7Mo samples nitrocarbu-
rized during 3 hours, shows a monotonic increase without visible stabi-
lization. The sample containing 0.6% C shows a strongly disturbed
curve after 12 m of sliding. This phenomenon can be explained by the
fragile degradation of the nitrocarburized layer and the formation of a
third body (oxide or nitride particles) detached from the surface [32].
However, the sample with the lesser content carbon shows a smooth-
er curve without visible disturbances, reflecting a deterioration by
abrasion without detachment of the particles. The coefficient of fric-
tion stabilizes after 15 m without significant deterioration of the sur-
face.
Fig. 7. Evolution of the coefficient of friction with sliding course for sintered
and nitrocarburized steels.
a b
Fig. 6. X-ray diffraction diagrams ( 1.54060 Å) nitrocarburized steel:
Fe0.4C2Cu2Ni0.7Mo (a), Fe0.6C2Cu2Ni0.7Mo (b).
EFFECT OF NITROCARBURIZING ON MECHANICAL PROPERTIES OF STEELS 525
The abrasive nature of the degradation of the surface is predomi-
nant for the nitrocarburized samples due to the presence of hard phas-
es such as iron oxides and nitrides.
4. CONCLUSION
In this work, new sintered steels have been developed by the powder
metallurgy technique under cold compaction. The structural, physical
and mechanical characteristics of the morphology were studied for dif-
ferent compositions of these steels.
This study allowed the determination of the parameters influencing
the development of low alloy sintered steels, the influence of alloying
elements during the compaction process (compressibility, green densi-
ty), and the effect of the carbon content on the microstructure, which
in turn affects the mechanical properties of these steels. Results
showed.
The minimum porosity is obtained by the use of very fine powders,
with sintering at high temperature with a long hold time.
High-temperature sintering favours homogenization of the material
due to a better diffusion of the alloying elements, which tend to fill the
small pores, and their shrinkage.
Mechanical tests have demonstrated the influence of the micro-
structure on the mechanical properties of these steels.
Nitrocarburization makes it possible to modify the nature and the
proportions of the formed phases, following a selective diffusion due
to the solid phase diffusion reactions of the group (C, N, O).
The presence of dispersed reinforcements such as nitrocarbides, ox-
ides and intermetallics due to the nitrocarburization can improve the
hardness from 235 to 247 HV depending on the additives content of the
salt bath.
The sintered samples exhibit similar wear behaviours and friction
coefficients during the first step from 0 to 10 m, considered as the lap-
ping step.
Beyond 10 m, the surface is hardened, and there is a sudden increase
in Cf, which is linked to the crushing of the surface asperities.
The greater presence of free graphite in the structure and the pres-
ence of elements such as Ni and Cu, which, by their action on the ther-
modynamic activity of carbon, favour the graphitization by creating
graphite nodules, which act as lubricant.
The very low friction coefficient observed at the beginning (Cf
0.1), increases significantly after a sliding distance of 15 m to reach
0.6 for the nitrocarburized samples.
The abrasive nature of the degradation of the surface is predomi-
nant for these samples due to the presence of hard phases such as iron
oxides and nitrides.
526 S. SERRAI, S. MECHACHTI, O. BENCHIHEUB et al.
REFERENCES
1. R. M. German, Powder Metallurgy of Iron and Steel (New York: John Willey
and Sons: 1998).
2. K. S. Narasimhan, Materials Chemical Physic, 67: 56 (2001).
3. R. J. Causton and J. J. Fulmer, Proc. Advances in Powder Metallurgy and
Particulate Materials, 5: 17 (1992).
4. V. A. Tracey, Proc. Conf. on Advances in Powder Metallurgy and Particulate
Materials (Eds. A. Lawley and A. Swanson) (California, USA: 1992), vol. 5,
p. 303.
5. G. S. Upadhyaya, Sintered Metallic and Ceramic Materials. Preparation,
Properties and Applications (New York: John Wiley and Sons: 2000).
6. H. Khorsand, S. M. Habibi, H. Yoozbashizadea, K. Janghorban,
S. M. S. Reihani, H. Rahmani Seraji, and M. Ashtari, Materials and Design,
23, Iss. 7: 667 (2002).
7. R. YIlmaz and A. Gökçe, Proc. 13th
International Metallurgy and Materials
Congress (Istanbul: 2006), p. 903.
8. R. YIlmaz and A. Gökçe, Proc. 11th
International Materials Symposium
(Denizli: 2006), p. 760.
9. R. YIlmaz, A. Gökçe, and H. Kapdibaú, Advanced Materials Research,
Materials and Technologies, 22–23: 71 (2007).
10. R. Yilmaz and Ö. Özgün, Proc. 14 the International Metallurgy and Materials
Congress (Istanbul: 2008).
11. N. Chawla, S. Polasik, K. S. Narasimhan, T. Murphy, M. Koopman, and
K. K. Chawla, Int. J. Powder Metall., 37: 49 (2001).
12. N. Chawla, T. F. Murphy, K. S. Narasimhan, M. Koopman, and K. K. Chawla,
Mater. Sci. Eng. A, 308, Iss. 1–2: 180 (2001).
13. N. Chawla, D. Babic, J. J. Williams, S. J. Polasik, M. Marucci, and
K. S. Narasimhan, Adv. Powder Metall. Part. Mater Metal Powder Industries
Federation, 5: 104 (2002).
14. S. J. Polasik, J. J. Williams, and N. Chawla, Metall. Mater. Trans. A, 33, Iss. 1:
73 (2002).
15. P. Lemieux, Y. Thomas, P. E. Mongeon, S. Pelletier, and S. St-Laurent, Powder
Metallurgy Technology, 24(3): 227 (2006).
16. Eprouvette Pour Essai de Traction, Norme ISO 2740 (2007).
17. Eprouvette Non Entaillée pour Essai de Résilience, Norme ISO 5754 (1978).
18. Détermination de la Résistance à la Rupture Transversale, Norme ISO 3325
(1996).
19. C. Ionici and D. Dobrota, Science of Sintering, 45, No. 1: 21 (2013).
20. S. M. Habibi, K. Janghorban, H. Khorsand, and S. A. J. Jahromi, Proc. 3
rd
International Powder Metallurgy Conference (Ankara: Turkish Powder
Metallurgy Association: 2002), p. 398.
21. E. Dudrova, M. Kabatova, R. Bidulsky, and A. S. Wronski, Powder Metallurgy,
47: 181 (2004).
22. Steel Heat Treatment. Handbook (Ed. G. E. Totten) (CRC Press: 2006).
23. Höganas Handbook for Sintered Components. Design and Mechanical
Properties (Höganas: 2004).
24. Höganas Handbook for Sintered Components. Production of Sintered
Components (Höganas: 2004).
https://doi.org/10.1016/S0254-0584(00)00420-X
https://doi.org/10.1016/S0261-3069(02)00046-8
https://doi.org/10.1016/S0261-3069(02)00046-8
https://doi.org/10.1016/S0921-5093(00)01990-0
https://doi.org/10.1007/s11661-002-0006-8
https://doi.org/10.1007/s11661-002-0006-8
https://doi.org/10.2298/SOS1301021I
https://doi.org/10.1179/003258904225015518
https://doi.org/10.1179/003258904225015518
EFFECT OF NITROCARBURIZING ON MECHANICAL PROPERTIES OF STEELS 527
25. A. Basu, J. Dutta Majumdar, J. Alphonsa, S. Mukherjee, and I. Manna, Mater.
Lett., 62: 3117 (2008).
26. F. Chagnon and L. Tremblay, World Congress and Exhibition (Vienna: 2004).
27. W. M. De Silva, R. Binder, and J. D. B. de Mello, Wear, 258: 166 (2005).
28. R. Hoffmann and K. H. Weissohn, The Use of Oxygen Probes in Nitriding and
Nitro-Carburizing, No. 267: 39 (1993).
29. D. Ghiglione, C. Louroux, and C. Tournier, Technique de L’ingénieur, M1227
(2002).
30. H. C. Pavanati, G. Strafellini, A. M. Maliska, and A. N. Klein, Wear, 265: 301
(2008).
31. N. Candela, F. Velasco, and J. M. Torralba, Materials Science and Engineering
A, 259, Iss. 1: 98 (1999).
32. P. Belkin, S. Kusmanov, A. Naumov, and Y. Parkaeva, Adv. Mater. Res., 704:
31 (2013).
https://doi.org/10.1016/j.matlet.2008.02.001
https://doi.org/10.1016/j.matlet.2008.02.001
https://doi.org/10.1016/j.wear.2004.09.042
https://doi.org/10.1016/j.wear.2007.10.014
https://doi.org/10.1016/j.wear.2007.10.014
https://doi.org/10.1016/S0921-5093(98)00865-X
https://doi.org/10.1016/S0921-5093(98)00865-X
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