M. KUØÍK et al.: STUDY OF THE PROPERTIES AND STRUCTURE OF SELECTED TOOL STEELS FOR COLD WORK ...
585–589
STUDY OF THE PROPERTIES AND STRUCTURE OF SELECTED
TOOL STEELS FOR COLD WORK DEPENDING ON THE
PARAMETERS OF HEAT TREATMENT
[TUDIJA LASTNOSTI IN STRUKTURE IZBRANIH ORODNIH
JEKEL ZA HLADNO OBLIKOVANJE V ODVISNOSTI OD
TOPLOTNE OBDELAVE
Martin Kuøík, Jakub Lacza, Tomá{ Vlach, Jana Sobotová
Czech Technical University, Faculty of Mechanical Engineering, Karlovo námesti 13, 121 35 Prague 2, Czech Republic
martin.kurik@fs.cvut.cz
Prejem rokopisa – received: 2016-06-20; sprejem za objavo – accepted for publication: 2016-12-09
doi:10.17222/mit.2016.120
Tool steels produced with powder metallurgy (P/M) are perspective materials, although they are more expensive in comparison
with tool steels produced with the conventional method. The work focuses on the study of mechanical properties and structure
depending on the heat-treatment conditions for the two tool steels. These are the 1.2379 steel for cold work produced with
classical metallurgy and high-speed P/M steel Vanadis 23. Both materials were heat treated in the conventional manner to
achieve a hardness of 61 HRC. They were also exposed to a cryogenic treatment at temperatures of –90 °C and –196 °C for 4 h
between the hardening and the tempering. We evaluated the hardness and strength using the three-point-bending test and the
wear resistance using the pin-on-disk method.
Keywords: powder metallurgy, high-speed steels, heat treatment, cryogenic treatment, wear rate
Orodna jekla, proizvedena s postopki metalurgije v prahu (angl. P/M) so perspektivni materiali, kljub temu da so dra`ji od tistih
izdelanih s konvencionalno metodo. Delo je osredoto~eno na {tudijo mehanskih lastnosti in strukturo, v odvisnosti od pogojev
toplotne obdelave za ti dve vrsti orodnih jekel. To so jekla 1.2379 za delo v hladnem, proizvedena s klasi~nimi metalur{kimi
postopki in hitrorezno P/M jeklo Vanadis 23. Oba materiala sta bila toplotno obdelana s konvencionalnimi postopki, glede na
njuno sestavo, tako, da sta dosegli trdnost 61 HRC. Bili sta tudi izpostavljeni obdelavi s podhlajevanjem pri temperaturah od
–90 °C in –196 °C za 4 h med strjevanjem in temperiranjem. Trdnost je bila ocenjena pri trito~kovnem mehanskem testu
(zvijanje) in s testom obrabe po metodi pin-on-disk.
Klju~ne besede: metalurgija prahov, visokorezna jekla, toplotna obdelava, obdelava s podhlajevanjem, stopnja obrabe
1 INTRODUCTION
It is well known that for tool steels at a given hard-
ness, the wear resistance may vary depending on the pa-
rameters of heat treatment and also on the mode of load
for the tool during its use in manufacturing. In addition,
we can assume that the resulting wear resistance will
also affect the method of producing the material itself.
As most of the tool steels are produced in the metallurgi-
cal process based on the solidification of the melt, this
method can be classified as conventional (C/M). This
metallurgy causes undesirable segregation that nega-
tively affects the primarily toughness. In the tool steels
produced with powder metallurgy (P/M), we achieve, in
comparison with C/M, a finer and more homogeneous
structure exhibiting better mechanical properties of the
tools, such as greater toughness and wear resistance at
higher cutting speeds.1 Although P/M tool steels are sev-
eral times more expensive compared with C/M steels,
they may be economically advantageous. The economic
benefit of their use is particularly significant in the appli-
cations where the replacement of the tools is time con-
suming.
The present work deals with a comparison of the
properties of selected tool steels for cold work with dif-
ferent primary-metallurgy steels, which were heat treated
in a conventional manner (CHT), i.e., quenched and mul-
tiply tempered. Currently, the cryogenic treatment is in-
creasingly used for tool steels.1–5 The aim is to obtain the
optimum ratio between contradictory properties, like
hardness and toughness, providing for a greater wear re-
sistance of the treated instruments.5 Authors attribute this
benefit of cryogenic treatment to the precipitation of
very fine carbides and a reduction of the proportion of
the residual austenite in the structure. Cryogenic treat-
ment usually takes place between quenching and temper-
ing; its main parameters are the temperature and the
holding time. Cryogenic treatment is generally divided,
according to the minimum temperature, into: shallow
cryogenic treatment (SCT), which is generally per-
formed in a temperature range from –80 °C to –140 °C
and deep cryogenic treatment (DCT), which is generally
performed at a temperature of –196 °C.5 It can be said
that, in the available literature, we can clearly find more
publications dedicated to monitoring the effect of
cryogenic treatment on the functional characteristics of
Materiali in tehnologije / Materials and technology 51 (2017) 4, 585–589 585
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Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 51(4)585(2017)
the C/M tool steel, compared with the publications that
address the same issue for the P/M steel. There are only
a few papers about the benefits of the cryogenic
treatment of high-speed steels (HSS).6,7 In the present
work, we observe the influence of heat treatment on the
properties of C/M tool steel 1.2379 and P/M HSS
Vanadis 23. The work is part of the solution of a problem
taken from practice, and the task is to find a more
suitable material for a tool for cold forming and specify
its heat treatment. A heat-treatment shop suggested to a
customer to use cryogenically treated steel Vanadis 23
(1.3395) instead of steel 1.2379 (X153CrMoV12, AISI
D2).
Steel 1.2379 is a C/M cold-work tool steel with high
carbon and chromium contents. The steel is character-
ized with a high wear resistance, high compressive
strength, good hardenability, high dimensional stability
and good resistance to tempering. It is recommended for
the tools that require a high wear resistance and suffi-
cient toughness. The maximum hardness in the soft-an-
nealed condition is 250 HBW. This steel is often used for
cryogenic treatment as reported in references.2–4 It is
noted that the steel showed an improvement in the wear
resistance after cryogenic processing. For example, Das
et al. investigated the effect of cryogenic treatment in-
cluding low-temperature quenching and low-temperature
tempering on the structure and properties of the 1.2379
steel.8,9 The authors conclude that both bulk hardness and
apparent hardness of the matrix of the 1.2379 steel in-
crease with the decreasing temperature of cryogenic
treatments; however, this effect is more pronounced for
the manifestation of the hardness of the matrix than of
the bulk hardness.8 Furthermore, the authors note that the
wear resistance of the 1.2379 steel gets considerably en-
hanced due to cryogenic treatment, compared to that of
the CHT one, irrespective of the holding time at
–196 °C.
The extent of the improvement in the wear resistance
monitored with a pin-on-disk tester, however, is depend-
ent on the test condition (using the normal load and slid-
ing velocity). The authors attribute this fact to the
wear-test condition, controlling the active mechanisms
and the mode of wear. It was found that the hardness of
the 1.2379 steel increases marginally due to cryogenic
treatment, in contrast to a significant increase in the wear
resistance. The most suitable parameters of DCT were
determined for the 1.2379 tool steel, which are
–196 °C/36 h for obtaining the best combination of the
desired microstructure and wear properties of the steel.9
It is necessary to mention that at the used cooling and
heating rate of 0.75 K/min during the cryogenic treat-
ment, the total time is 46 hours for DCT. Generally,
when the time is longer, the processing is more expen-
sive. This fact must also be included in the design of the
parameters of DCT for real tools.10
Vanadis 23 (1.3395) is a chromium-molybde-
num-tungsten-vanadium-alloyed high-speed P/M steel
which is characterized by an excellent combination of
wear resistance and toughness, correct hardness for the
application, very good dimensional stability during heat
treatment and temper resistance. The maximum hardness
in the soft-annealed condition is 260 HBW. It is espe-
cially suitable for blanking and forming thinner work
materials where mixed (abrasive-adhesive) or abrasive
types of the wear are encountered and where the risk for
a plastic deformation of the working surface of a tool is
high. We do not know of a research in the literature that
would resolve the influence of heat-treatment conditions
on the properties of this steel. However, C/M high-speed
steel 1.3343 (AISI M2) is often used for cryogenic treat-
ment according to references,6,11–12 as it has low carbon
and vanadium contents in comparison with the other type
of steel. Reference12 notes that no significant impact of
DCT on the final hardness of steel 1.3343 was not
proven, while its positive effect on the wear resistance
was demonstrated. The wear resistance was observed to
be greater by 44 % after DCT, in comparison with that
obtained after CHT using laboratory tests.
The tool life of twist drills made of steel increased af-
ter DCT, depending on the cutting conditions, in a range
of 65–343 %. Conversely, reference11 notes that the hard-
ness and also the wear resistance increase after DCT for
steel 1.3343. A 6 % increase in the hardness and a 35 %
increase in the wear resistance are established. It is stated
in reference6 that moderate increases in the hardness and
fracture toughness after DCT for steel 1.3343 result in a
better wear resistance than in the case when only one of
the parameters is extremely high. However, reference7
observes that the influence of DCT was not found for the
hardness of P/M HSS Vanadis 30.
The aim of the present work was to investigate the ef-
fects of SCT and DCT taking place between quenching
and tempering on the properties and structures of the two
above-mentioned tool steels.
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586 Materiali in tehnologije / Materials and technology 51 (2017) 4, 585–589
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Table 1: Heat treatment of the experimental materials
Material Quenching Cryogenic treatment Tempering Designation of the regime
1.2379 1050 °C/30 min – 2× 500 °C/2 h CHT
1.2379 1050 °C/30 min –90 °C/4 h 2× 500 °C/2 h SCT
1.2379 1050 °C/30 min –196 °C/4 h 2× 500 °C/2 h DCT
Vanadis 23 1050 °C/5 min – 3× 560 °C/1 h CHT
Vanadis 23 1050 °C/5 min –90 °C/4 h 3× 560 °C/1 h SCT
Vanadis 23 1050 °C/5 min –196 °C/4 h 3× 560 °C/1 h DCT
2 EXPERIMENTAL PART
The experimental material included commercial C/M
cold-work steel 1.2379 (X153CrMoV12, AISI D2), nom-
inally containing (in mass fractions, w/%) 1,53 % C,
0,35 % Si, 0,45 % Mn, 12,00 % Cr, 0,85 % Mo,
0,85 % V and P/M HSS Vanadis 23 (1.3395) nominally
containing (in mass fractions, w/%) 1,29 % C, 058 % Si,
0,29 % Mn, 0,024 % P, 0,014 % S, 4,02 % Cr,
4,91 % Mo, 6,13 % W, 2,97 % V. The choice of the ma-
terials was explained in the introduction. Samples for the
three-point-bending test (10 × 10 × 100 mm with surface
roughness of 0.2–0.3 μm) were made from the two mate-
rials. CHT consisted of the following steps for both ma-
terials: austenitizing, quenching and double or triple tem-
pering. Cryogenic processing also included hardening
and tempering of each material. The heat-treatment re-
gime is shown in Table 1. Five samples of each series
were processed.
The distance between supports was 80 mm during the
three-point-bending test; the loading rate was 1 mm/min
up to the moment of fracture. The average values and
standard deviation were calculated from the measured
values. Broken specimens were used for measuring the
HRC hardness. The hardness was measured five times on
each sample and the average values and standard devia-
tion were calculated. One specimen whose strength was
close to the average value was chosen from each series.
These samples served for a metallographic analysis and
the measurement of the wear resistance. A basic metallo-
graphic analysis was performed using light microscopy
of cross-section samples. Metallographic samples were
prepared in the standard way and etched with 2 % Nital.
SEM micrograhps were taken with a JOEL
JSM7600F device. The wear resistance was determined
with the pin-on-disk tester in line with the standard.13 As
the disk was used for testing the material, its surface was
polished to a surface roughness better than 0.04 μm. The
test was carried out under dry sliding conditions, per-
formed at a room temperature of 22 °C and relatively hu-
midity of 60 %. All the specimens were ultrasonically
cleaned in ethanol and dried in air. An Al2O3 ball of  6
mm was used as the counterpart. The sliding speed was
6.4 cm/s, the total sliding distance was 100 m and the
scratch radius was 4 mm. The width of scratches was
evaluated with light microscopy using a Nis Elements
image analyser, always at six locations. The average
value was calculated and the wear rate was determined.
Control measurements were performed in the transverse
area of the scratches using a profilometer, recording a
good range of the results.
3 RESULTS AND DISCUSSION
The bending strength for both materials is shown in
Figure 1. As expected, the strength of steel Vanadis 23 is
about 1000 MPa higher than that of steel 1.2379. As
stated by the author in reference14, the flexural strength is
dependent, among other things, on the size and distribu-
tion of carbides. For steel Vanadis 23, a more uniform
distribution of small carbides is expected than in the case
of steel 1.2379. Fracture was always brittle to form two
large parts and small fragments of the fracture surface.
The measurement was conducted only for the purpose of
comparison.
It can be concluded that the bending strength was al-
most identical depending on the heat treatment of both
steels. This result is in good agreement with the results
of previous works.7,15 As expected, the hardness of steel
Vanadis 23 is 1–2 HRC higher than the hardness of steel
1.2379 (Figure 2).
It seems that the hardness values slightly decreased
for the two reference materials after cryogenic process-
ing, which is in good agreement with the results of moni-
toring the impact of cryogenic treatment on the proper-
ties of P/M tool steel Vanadis 6.15,16 On the contrary, D.
Das8 concluded that both the bulk hardness and the ap-
parent hardness of the matrix increase with the decreas-
ing temperature of cryogenic treatments of the C/M
1.2379 steel, and that the degree of influence of cryo-
genic treatment on the hardness is dependent on the pa-
rameters of the heat treatment (the temperature and time
of austenizing and tempering) as well as the rate of cool-
ing, depth of cryogenic treatment and holding time.
However, it should be noted that in his case, low-temper-
ature tempering was used.
The microstructures of steels 1.2379 and Vanadis 23
after CHT and DCT are shown in Figure 3. The micro-
structure of both steels consists of the matrix and car-
bides. The distribution and size of carbides differ, de-
M. KUØÍK et al.: STUDY OF THE PROPERTIES AND STRUCTURE OF SELECTED TOOL STEELS FOR COLD WORK ...
Materiali in tehnologije / Materials and technology 51 (2017) 4, 585–589 587
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 2: Influence of heat treatment on the hardness of 1.2379 and
Vanadis 23 steels
Figure 1: Influence of heat treatment on the bending strength of
1.2379 and Vanadis 23 steels
pending on the method of steelmaking (C/M or P/M).
The banding carbides observed in steel 1.2379 confirm
the measurement of the bending strength. In both cases,
the matrix mainly contains tempered martensite. Minor
phases include retained austenite. It can be expected that
the amount of retained austenite and precipitated fine
carbides is smaller after DCT than after CHT.2–4
The SEM analysis did not show any significant dif-
ferences in the structure between CHT, SCT and DCT.
No significant areas of residual austenite were observed,
as illustrated in Figure 4. A TEM analysis was necessary
for an accurate determination of the amount of residual
austenite. In both cases, we observed small carbides with
sizes smaller than 1 micron, but in the case of Vana-
dis 23, their amount was significantly larger. Moreover,
its structure included carbides with sizes of 100–200 nm.
The wear rate was determined for both materials and
monitored states (Figure 5). As expected, it is seen that
the wear-rate values are much lower for Vanadis 23 than
for steel 1.2379. The wear rate of steel Vanadis 23 de-
pends on the heat treatment, but it varies minimally. It
was necessary to verify the value of the wear rate of steel
1.2379 after SCT. The existing results and the results
from reference9 do not indicate that the wear rate should
be lower after SCT than after DCT of the 1.2379 steel.
Based on these laboratory results, it is possible to believe
that Vanadis 23 is a suitable material for the replacement
of steel 1.2379 in the case of cold forming. Although the
current results of the pin-on-disk test do not conform to
our assumption, it can be assumed that the tools made of
steel Vanadis 23 using DCT have better wear resistance
than the tools after CHT. The results may be distorted
because the formed wear-track width was between
200–300 microns, which is about 5 % of the diameter of
the inserted Al2O3 ball. Based on this finding, it would
be preferable to use a larger normal load for the
pin-on-disc test for the wear-track width to be in a range
of 20–80 % of the ball diameter. Yan10 states that al-
though the hardness and wear tests provided information
on the properties of the cryogenically treated HSS, they
may not properly represent the loads of real tools in the
operating conditions. For this reason, the heat treatment
of P/M HSS Vanadis 23 will be recommended after a du-
rability test of real tools.
4 CONCLUSIONS
The obtained results and our pertinent discussion al-
low us to infer the following:
• The bending-strength values were almost identical af-
ter the conventional and cryogenic treatment of C/M
tool steel 1.2379 and P/M HSS Vanadis 23. The
strength of steel Vanadis 23 was about 1000 MPa
higher than that of steel 1.2379 in all the modes of
heat treatment.
• The hardness values for the two reference materials
slightly decreased after the cryogenic processing. The
hardness of steel Vanadis 23 was 1–2 HRC higher
than the hardness of steel 1.2379.
M. KUØÍK et al.: STUDY OF THE PROPERTIES AND STRUCTURE OF SELECTED TOOL STEELS FOR COLD WORK ...
588 Materiali in tehnologije / Materials and technology 51 (2017) 4, 585–589
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 5: Influence of heat treatment on the wear rate of 1.2379 and
Vanadis 23 steels
Figure 3: Microstructures of 1.2379 and Vanadis 23 steels after CHT
and DCT
Figure 4: SEM micrographs of 1.2379 and Vanadis 23 steels after
CHT and DCT
• Light metallography is not appropriate for investigat-
ing structural changes after the cryogenic treatment
of the 1.2379 and Vanadis 23 steel.
• The wear-rate values are much lower for Vanadis 23
than for steel 1.2379.
• Based on these laboratory results, Vanadis 23 is a
suitable material for the replacement of steel 1.2379
in the case of cold forming.
• The inclusion of a cryogenic treatment in the conven-
tional heat treatment of Vanadis 23 will be decided
on after a durability test of real tools.
Acknowledgements
This work was supported by the Ministry of Educa-
tion, Youth and Sport of the Czech Republic, programe
NPU1, project No. LO1207 and by the Grant Agency of
the Czech Technical University in Prague, grant No.
SGS15/149/OHK2/2T/12.
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