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INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
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ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XV, Issue III, March 2026
“Effect of Heat Treatment Variables on Microstructure and Mechanical
Properties of Aisi 4130 Low Alloy Steel’’
Jignasha Parmar
1
*, Dr. Vandana J Rao
2
1
Assistant Professor, Department of Metallurgical and materials Engineering, [The maharaja Sayajirao
university], Baroda, India
2
Associate Professor, Department of Metallurgical and materials Engineering, [The maharaja Sayajirao
university], Baroda, India
DOI:
https://doi.org/10.51583/IJLTEMAS.2026.150300102
Received: 31 March 2026; March: 06 April 2026; Published: 21 April 2026
ABSTRACT
The present study investigates the effect of heat treatment on the microstructure and mechanical properties of
AISI 4130 steel. The material was subjected to a sequence of normalizing, hardening, and tempering treatments
to evaluate the influence of tempering temperature on performance characteristics. Normalizing was carried out
at 890°C followed by air cooling, resulting in a refined ferrite–pearlite microstructure. Subsequently, hardening
was performed at 860°C and followed by quenching to obtain a martensitic structure.
Tempering was conducted at two different temperatures, 472°C (Sample A) and 518°C (Sample B), to study the
variation in mechanical behavior.
The results highlight that tempering temperature plays a critical role in tailoring the balance between strength
and toughness in AISI 4130 steel. This study provides useful insights for optimizing heat treatment parameters
for engineering applications requiring a combination of mechanical performance and structural reliability.
Keywords: Heat treatment, Normalizing, Hardening, Tempering
INTRODUCTION
In this modern world we come across various engineering materials, but when these materials are scrutinized,
we find that steel remains predominant. Steel has provided modern engineer the leverage to tailor engineering
components ranging from a small nut to huge skyscrapers.
Amongst various classes of steel, medium carbon steels stand apart and are considered to be the backbone of
modern industry. Steel can briefly be divided into three types; one of them is medium carbon steel. A medium
carbon steel having 0.80-1.10% Cr, 1% Ni and 0.28-0.33 C with Tempered Martensite structure can be
considered as a medium carbon steel. Medium carbon steels occupy a unique status as engineering materials by
virtue of their excellent combination of properties such as high strength, adequate ductility, toughness and good
corrosion resistance. These steels find extensive application in chemical plants, power generation equipment’s,
in gas turbines as turbine and compressor blades and discs, aircraft engine components and fittings and in marine
components.
These steels can be heat treated to obtain a wide range of mechanical properties to meet the requirements of
specific application AISI 4130 is one of the most potentially attractive steels in this medium carbon steel class
used extensively for parts requiring a combination of high tensile strength, good toughness and corrosion
resistance. 4130 is a high chromium-low nickel low hardenability Medium carbon steel and generally used as
hardened and tempered in the tensile range 655 min MPa, Brinell range 204-244 BHN. Characterised by very
good corrosion resistance in general atmospheric corrosive environments, good resistance to mild marine and
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industrial atmospheres, resistant to many organic materials, nitric acid and petroleum products coupled with high
tensile and high yield strength plus excellent toughness in the hardened and tempered condition. So AISI 4130
is used in highly-stressed aircraft components, pump shafts and valve stems etc.
Generally heavy components of AISI 4130 steel like shaft, axle etc can be manufactured by open die hot forging
(heavy forging). The forging of type AISI 4130 steel is carried out between the ranges of 900 to 1200 °C followed
by slow cooling up to room temperature. The slow cooling of materials shall be done by either furnace or
insulating materials. Normalizing process (after cooling of heavy forged part) immediately required for forged
products to make them machinable after normalizing followed hardening and tempering.
Experimental Work
Five specimens were prepared for microstructural characterization and mechanical testing, including hardness,
tensile, and impact tests. Metallographic preparation was carried out in accordance with ASTM E3, followed by
etching as per ASTM E407 to reveal the microstructure. Brinell hardness measurements were performed
according to ASTM E10 using a standard ball indenter, and the reported values represent the average of three
readings. Tensile testing was conducted in accordance with ASTM E8/E8M using a universal testing machine
to determine strength and ductility parameters. Impact toughness was evaluated using the Charpy impact test as
per ASTM E23.
Figure 1: Microstructure of normalized Steel Specimen (Ferrite-pearlite),2% Nital
100 X
200 X
400 X
1000 X
Table 1: Parameter variables
Object dimension (mm)
Normalizing Temp (
o
C)
Tempering Temp (
o
C)
Sample A (390 Ø x 265) L
860
o
C
450 + 22 = 472
Sample B (390 Ø x 265) L
860
o
C
472 + 46 =518
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Experiment for Sample A
Hardening
Figure 2: Heat Treatment Cycle showing hardened Sample A at 860
o
C(Holding time 8Hrs) and water
Quenched, Resulting in Approximately cooling rate (0.64 °C/s ).
Tempering
Figure 3: The hardened sample A Was Tempered at 472
o
C, for 13 hr and air cooled.
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Experiment for Sample B
Hardening
Figure 4: Heat Treatment Cycle showing hardened Sample B at 860
o
C (Holding time 8 Hrs) and water
Quenched, Resulting in Approximately cooling rate (0.11 °C/s )
Tempering
Figure 5: Tempering cycle Shows The hardened sample B Was Tempered at 518
o
C, for 13 hr and air
cooled.
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RESULTS
Table 2: Result for Sample A (Tensile, Micro and Impact Testing)
Sample
(Ø390 X 265
mm L)
Hardness after tempering at30 mm
depth
A
262,252,262
Yield strength
(MPa)
Tensile
Strength
(MPa)
Elongation
(%)
Reduction
Area (%)
Impact (Charpy V
notch) Temp
– 45
o
C (J)
Avg.
L = 687
903
25
58.946
26,23,7
18.66
T = 816
908
25.30
55.198
12,19,10
13.6
R= 663
869
14.680
51.045
19,16,25
20
Where L = Longitudinal Direction, T = Transverse Direction, R=Radial Direction
Table 3: Result of Tensile Testing, Impact & Hardness to Experiment
Sample
(Ø390 X 265 mm
L)
Hardness after hardening
at 860
o
C (BHN)
Hardness after tempering
at 518
o
C (BHN)
Hardness after tempering
at 30 mm depth
B
382, 400, 419
382, 364, 400
242, 232, 242
Yield strength
(MPa)
Tensile
Strength
(MPa)
Elongation
(%)
Reduction
Area (%)
Impact (Charpy V
notch) Temp
– 45
o
C (J)
Avg.
L = 731
879
24.16
58.593
28,12,32
24
T = 730
887
22.02
50.709
30,20,13
21
R= 667
861
19.28
53.651
28,40,30
32.66
Where L = Longitudinal Direction, T = Transverse Direction, R=Radial Direction
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Microstructure Analysis after tempering
Figure 6: Microstructure of Tempered Sample A (tempered martensite & upper bainite, blue colour shows
tempered martensite), Etchant Berasas.
100X
400X
Figure 7: Microstructure of Tempered Sample B (tempered martensite), Etchant 2% Nital
100X
400X
DISCUSSIONS
Normalizing at 890°C followed by air cooling resulted in a ferrite–pearlite microstructure due to the
transformation of austenite under relatively slow cooling conditions. This microstructure provides a uniform and
balanced combination of strength and ductility, serving as a suitable base for subsequent heat treatment. After
quenching and tempering, the microstructure revealed the presence of tempered martensite and upper bainite.
The blue-colored regions observed in the microstructure correspond to tempered martensite when etched with
Berasa reagent, while 2% Nital etching confirmed the presence of tempered martensite. The formation of these
phases indicates partial decomposition of martensite during tempering, contributing to improved toughness and
reduced brittleness.
The cooling behavior significantly influenced phase transformation and mechanical properties. Experiment 1
exhibited a higher cooling rate (0.64 °C/s), whereas Experiment 2 showed a lower cooling rate (0.11 °C/s).
Tempering at 472°C and 518°C reduced hardness and enhanced toughness, with higher tempering temperature
promoting carbide coarsening and improved impact strength. A hardness gradient across the section was
observed due to non-uniform cooling in the large specimen.
CONCLUSIONS
Hardening at 860°C followed by tempering significantly influences the balance between strength and toughness
of the material.
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Tempering at 472°C (Experiment 1) resulted in higher ultimate tensile strength but comparatively lower impact
toughness due to the presence of tempered martensite along with upper bainite.
Tempering at 518°C (Experiment 2) led to improved impact energy and better toughness, attributed to the
formation of a more uniform tempered martensitic structure.
REFRENCES
1. Poloprudský, J., Chlupová, A., Šulák, I., & Obrtlík, K. (2023). Effect of heat treatment on the
microstructure and fatigue behaviour of AISI 4130 steel. Metallic Materials/Kovove Materialy, 61(6).
2. Heidary, O., Mirzaee, O., Raouf, A. H., & Borhani, E. (2020). UP-quenched SAE 4130 steel:
Mechanical properties assessment and bainite formation. Materials Science and Engineering: A, 787,
139479.
3. Kachomba, T., Mutua, J., & Ngoret, J. (2024). The Effects of Heat Treatment on Mechanical Properties
and Microstructure of Wire-arc Additive Remanufacturing of AISI 4130 Steel Components. SSRG Int.
J. Mech. Eng., 11(4), 40-55.
4. ASM Handbook volume 1 Properties & selection Irons steels & High performance alloys
5. ASM Handbook Volume 14 – Forming & Forging..
6. Heat treatment - Principles & Techniques by T.V. Rajan
7. Metallographic Handbook by George F. Vander Voort.
8. Microscale & Macroscale Techniques in the Organic Laboratory by Mayo et al.
9. Physical metallurgy by Vijendra Singh.
10. Steels: Heat Treatment & Processing Principles by George Krauss