Open AccessArticle

Sliding Wear Behavior of WP7V Tool Steel with Different Hardnesses Under Reciprocating Test Rig

Rogério Breganon

¹,

Francisco Arieta

² and

Giuseppe Pintaude

^1,*

Surface and Contact Lab (LASC), Academic Department of Mechanics, Universidade Tecnológica Federal do Paraná, Curitiba 81280-340, Brazil

Tribosystems, R. Teixeira da Silva, 487 AP23, São Paulo 04002-032, Brazil

Author to whom correspondence should be addressed.

Lubricants 2024, 12(12), 453; https://doi.org/10.3390/lubricants12120453

Submission received: 19 November 2024 / Revised: 2 December 2024 / Accepted: 13 December 2024 / Published: 18 December 2024

(This article belongs to the Special Issue Recent Advances in Tribological Properties of Machine Tools)

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Abstract

This study involved the investigation of the mechanical and tribological behaviors of DIN 1.2344 and WP7V tool steels, quenched in a salt bath after austenitization at 1050 °C, followed by triple tempering for 2 h. The selection of tempering temperatures produced two hardness levels under four metallurgical conditions, with the hardest level found only for WP7V steel (54 and 57 HRC). The mechanical properties were evaluated using Rockwell C, Vickers, and nanoindentation methods, along with unnotched impact tests, according to the SEP 1314 guidelines. Wear tests were conducted in a tribometer configured for a reciprocating setup, with a frequency of 5 Hz, a load of 25 N, and a time of 60 min, at room temperature and at 200 °C. As counterbodies, alumina balls of 5 mm in diameter were used. Wear tracks were evaluated through scanning electron microscopy, EDS, interferometry, and Raman spectroscopy. Friction and wear behaviors were affected by the variation in temperature for softer steels (DIN 1.2344 and WP7V of 48.5 HRC): the higher the temperature, the better the tribological performance. The harder steels were not sensitive to temperature testing. These effects depend on maintaining iron oxide (hematite) at the point of contact. The wear rates determined for the hardest material (57 HRC), considering its impact resistance, make it unsuitable for severe conditions such as hot stamping.

Keywords:

tool steel; reciprocating; tribology

1. Introduction

The development of new classes of steels used as hot stamping tools in Germany and other European countries has become necessary due to the insufficient wear resistance of DIN 1.2344 and DIN 1.22367 steel. With this in mind, WP7V steel, widely used by the largest hot stamping companies across Europe, deserves attention.

The service life of tools used for hot stamping and cutting is not just a question of wear resistance and resistance to thermal fatigue. There are other requirements to be met that vary from tool to tool, since, in addition to offering high hardness and good wear resistance, they must also have sufficient toughness to prevent cracking due to thermal and mechanical overloads [1].

The properties of tool steel can be improved by controlling quenching heat treatment, with austenitizing temperatures of 1000 °C to 1060 °C. Subsequent tempering produces significant changes in the microstructure of the steel and enables the development of a wide range of properties. Heat treatment is used to increase not only hardness but also strength and toughness [2].

A comparison of DIN 1.2344, DIN 1.2367, and WP7V steels was presented in a study by Escher and Wilzer [1]. Globally, DIN 1.2344 steel is the most widely used steel for processes such as the forging and hot extrusion of steel, as well as for the hot extrusion of aluminum and for hot stamping tools. It exhibits a combination of high toughness, good mechanical resistance, good wear under hot temperatures, and lower costs. In comparison to DIN 1.2344, DIN 1.2367 steel has a lower carbon, vanadium, and silicon content and a higher molybdenum content, giving it superior hot mechanical resistance. This, together with its good toughness and thermal conductivity, means that this steel exhibits exceptional resistance to thermal fatigue, a very important property in aluminum injection and the hot forging of steels, and it can be used as an alternative to DIN 1.2344 in hot stamping tooling. WP7V has a much higher carbon, chromium, and vanadium content than the others, and while it has lower impact toughness and thermal conductivity, it has superior wear resistance.

Adhesive and abrasive wear are generally the wear mechanisms that limit tool life in dry metal-forming operations. Therefore, experience and experimentation in tool steel production and coating combinations are the most effective ways to identify the optimum tool steel for the application [3].

In a study conducted by Hardell and Prakash [4] involving sliding tests of tool steels and high-strength steel using temperatures of 40, 400, and 800 °C, the results showed that the friction and wear of the samples were temperature-dependent. The friction decreased and the tool steel wear increased with increasing temperature.

Gracia-Escosa et al. [5] observed oxidative wear mechanisms during the pin-on-disk test in addition to adhesion and abrasion tests. Abrasive wear is likely caused by the formation and fracture of oxides at high temperatures.

Cui et al. [6] performed wear tests on AISI H13 steel heat-treated at different tempering temperatures. The tests were carried out at room temperature, 200 °C, and 400 °C. The results showed that the wear rate at 200 °C was substantially lower than at room temperature and 400 °C; this was attributed to the protection of tribo-oxides. At room temperature, only a small amount of oxide appeared on the worn surfaces. At a temperature of 200 °C, the predominant tribo-oxides were Fe₃O₄ and Fe₂O₃.

The results of sliding wear tests conducted by Hardell et al. [7] showed a reduction in wear by three orders of magnitude and in friction by 50% when the temperature was increased from room temperature to 400 °C. This was attributed to the formation of a composite layer involving a hardened layer and a protective oxide layer. Reciprocating sliding facilitated the formation of a continuous oxide layer on both interacting surfaces compared to unidirectional sliding.

In terms of performance, two investigations deserve attention. The first is that of Karakurt et al. [8], who tested 1.2344 and WP7V steels after the same cycles of heat treatment (quenching and tempering). The steels reached a similar hardness, around 56 HRC. Unfortunately, these authors did not mention any aspect regarding impact resistance, which is crucial for selecting the most suitable metallurgical condition for dies. Their study also did not include a description of any physical reasons for the better performance of WP7V steel under pin-on-disk tests at 25 and 400 °C. However, a more elaborate investigation was conducted by Muro et al. [9]; these researchers used an SRV reciprocating test rig, where three tool steels were placed into contact with pins of 22MnB5 uncoated steel. Tests were performed at 40 and 200 °C, and the authors justified the slight drop in friction coefficient at high temperatures due to the formation of an oxide layer.

Conversely, the wear rates were higher for the tests performed at 200 °C. Although the authors identified the wear of the pins, they did not describe the worn surfaces, making it difficult to interpret the tribological results. Finally, the investigation also claimed another set of properties besides Rockwell C or Vickers hardness.

Considering the relevance of oxide in the tribological behavior of tool steels at high temperatures and that the previous investigation did not consider the impact resistance as a criterion for better material selection, we investigated the tribological behavior of tool steels usually employed for hot stamping dies via a reciprocating sliding test conducted at room temperature and 200 °C. For comparative purposes, two levels of hardness were investigated.

2. Materials and Methods

2.1. Tool Steels

Two types of tool steel, DIN 1.2344 (X40CrMoV5-1) and WP7V, were investigated, supplied in blank form with dimensions of 55 mm × 240 mm × 250 mm and 55 mm × 200 mm × 325 mm, respectively, and machined in the dimensions of 36 mm × 19 mm × 8 mm (Figure 1, specimen for the wear test). The wear surface was ground with Sa ≤ 0.23 µm.

The chemical composition of steels (in % wt.) was determined using a Bruker Tasman spectrometer, according to ASTM E415 [10]. The composition of 1.2344 steel is 0.365% C, 0.93% Si, 0.35% Mn, 4.89% Cr, 1.0% Mo, and 0.9% V, while WP7V steel contains 0.47% C, 0.87% Si, 0.37% Mn, 7.36% Cr, 1.11% Mo, and 1.22% V. Both contain W, S, and P at 0.1% or less.

The tool steel samples were quenched using a salt bath at Angra Tecnologia em Materiais at 1050 °C for 20 min as an autenitization step. After quenching, 3 cycles of tempering were performed for 2 h: 600 °C for 1.2344 steel, and 530, 550, or 575 °C for WP7V steel.

2.2. Hardness and Impact Tests

Rockwell C hardness (HRC, 150 kg) measurements were taken using a Mitutoyo HR-300 digital hardness tester (Mitutoyo Sul America Ltda, Jundiaí, Brazil), and microhardness measurements were taken with a Vickers microhardness tester, Mitutoyo—Hm 100 series (Mitutoyo Corporation, Kawasaki, Japan), applying 300 gf of load. The average values were calculated from a series of 3 measurements performed on each sample.

Nanohardness measurements were also performed. The measurements occurred randomly in the central region of the sample, corresponding to the same region where the wear tracks were determined but did not correspond to any hardening effect once they were measured before the wear test. For the instrumented indentation technique, the ZHN universal nanomechanical testing equipment from Zwick/Roell (Zwick/Roell, Ulm, Germany) was used. In this test, a Berkovich-type pyramidal indenter was used, with a load of 50 mN in a 5 × 6 matrix with a spacing of 30 µm × 30 µm, following the recommendations of ISO 14577 [11]. At the same time, we determined the elastic modulus for the metallic matrices of steels using indentation tests.

For the impact tests, unnotched 10 ± 0.1 × 55 ± 1 × 7 ± 0.1 mm samples were prepared according to SEP 1314 (Stahl-Eisen-Prüfblatt, SEP 1314-April 1990). The contact surface was ground using an impact hammer for Ra ≤ 0.2 µm. All samples were prepared following the same cutting orientation. The impact test was performed on the Time 800 J testing machine. The fractured surfaces were analyzed using a scanning electron microscope (Zeiss EVO-MA15, Oberkochen, Germany) to verify the predominant fracture mode.

2.3. Tribological Experiments

The tribological tests were performed in reciprocating mode, under dry conditions, using the UMT Multi-Specimen Test System tribometer, model CETR, from the manufacturer Bruker (Bruker, Campbell, CA, USA). The equipment used a load cell with a load capacity of 2 to 200 N and a resolution of 10 mN. A support with a long hollow shaft that extended into the chamber was used to fix the ball. The shaft restricts the heat transfer from the ball to the load cell. The load cell is also protected by a heat sink mounted between the support and the cell. The average values of the coefficient of friction (COF) were measured and acquired through the equipment software.

The testing conditions were a frequency of 5 Hz, a testing time of 60 min, a load of 25 N, and a temperature of 200 °C, in addition to room temperature (RT). Alumina balls (Al₂O₃) measuring 5 mm in diameter were used as counterbodies. Alumina was chosen to ensure the presence of aluminum at the contact, as Al-Si is the preferred coating to prevent oxidation on the surfaces of hot-stamped steel sheets [12,13].

All samples were ultrasonically cleaned in hexane and isopropyl alcohol and dried before each test. The average values of the wear rates were calculated from a series of 3 runs for each metallurgical condition.

For the room- and high-temperature tests, a chamber that is part of the equipment’s drive/chamber combination was used. It is mounted on the linear reciprocating drive structure. A heating element and a temperature sensor are located inside the chamber. A temperature controller uses the output of the temperature sensor to control the chamber temperature. The chamber has an access slot in the top cover to allow the attachment of the sample, held in place by two pins, to a load cell. A simplified scheme of the experimental setup is illustrated in Figure 2.

The high-temperature tests involved an initial heating sequence lasting approximately 17 min. The test was only performed after reaching the selected temperature.

The specific wear rate (SWR) was determined based on the measured wear volume of the worn tracks. The width, depth, and area of the worn tracks (Figure 3) were measured using a non-contact white light 3D profilometer (Talysurf CCI Lite Non-contact 3D Profilometer, Taylor Hobson, Leicester, UK).

The specific wear rate (SWR) was calculated using Equations (1) and (2) according to ASTM G133-05 [14].

S p e c i f i c w e a r r a t e (S W R) = \frac{W e a r v o l u m e}{T o t a l s l i d i n g d i s t a n c e (L) * L o a d}

(1)

The total sliding distance (L) is given by Equation (2).

L = 0.002 * f * t * l

(2)

where f is the frequency in Hz, t is the total sliding duration in sec, and l is the stroke length in mm.

After the tribological tests, the worn surfaces were characterized using a scanning electron microscope, 3D profilometer, and Raman microscopy. Raman spectroscopy was performed with a WITec alpha 300R Confocal Raman Microscope (WITec, Ulm, Germany) with a lateral resolution of 200 nm and a vertical resolution of 500 nm.

3. Results and Discussion

3.1. Microstructural Characterization and Mechanical Properties

The microstructure of heat-treated steels is shown in Figure 4. The presence of tempered martensite with small amounts of carbides is observed. Similar features were presented elsewhere for AISI H13 steel [6] and DIN 1.2346 steel [15].

Table 1 presents the hardness values obtained using the HRC scale, Vickers microhardness, and elastic modulus from indentation tests for the studied steels.

The differences between 1.2344 steel and WP7V at the same hardness level disappear when one considers the microhardness. There is no variation in the elastic modulus with the different heat treatments, as expected.

Figure 5 shows that, within the indentation matrix, random measurements were detected, indicating the presence of carbides on the microstructure of the WP7V steel samples of 48.5 and 54 HRC. The obtained values of 15.7 and 16.7 GPa, respectively, fall within the range of those reported by Casellas et al. [16] for M₇C₃ stoichiometry, meaning that we also likely identified this kind of carbide.

Another relevant aspect observed from Figure 2 is that the metallic matrix hardness values of the 1.2344 and WP7V steels treated for a low hardness level are similar, allowing for a comparison to be made between WP7V and a reference material.

Table 2 presents the results of the impact test. The results align with the expectation: the higher the hardness, the lower the absorbed impact energy.

Figure 6 shows the fractographies of the unnotched samples. The figure shows that the fractures are characterized as mixed, with proportions between semi-cleavage and micro-cavities, along with transgranular aspects. The variation in hardness from 48.5 to 57 HRC had little effect on the impact behavior of the WP7V steel, both in the predominance of fracture aspects and the average impact resistance values. Mixed fractures are frequently reported in the literature for AISI H13 steel (1.2344) [2,17,18,19,20].

It is worth noting the much higher deviation for the conditions of 48.5 and 54 HRC, which may be related to variations along the extraction sections of the test specimens. It is possible that there is a greater presence of micro-cavities that affect the hardness of 54 HRC, while in the case of 57 HRC, a significant number of facets that characterize the transgranular fracture are present.

Regarding the lower hardness range, DIN 1.2344 steel exhibited an impact resistance approximately 2.6 times greater than WP7V steel.

3.2. Friction and Wear Determination

Figure 7 shows the evolution of the coefficient of friction (COF) for each test condition. The average COF was calculated by running three tests, removing the running-in region, and considering only the stable region of the curve, with the time starting at 120 s and ending at 3600 s, as shown in Table 3.

The results show that, in the tests with the softest steels, the increase in the test temperature reduced the COF values. A peak in the COF signal was observed for the tests conducted at RT. Conversely, harder steels were not sensitive to the effect of temperature.

The width of the wear tracks was measured using interferometry analysis, and the results are presented in Table 4.

Figure 8 shows the specific wear rate (SWR) for the tests at RT and 200 °C.

As can be seen in Figure 8, the wear rates can be separated as a function of hardness level. This is more evident for the tests performed at room temperature, even though the harder steels (54/57 HRC) performed better than the softer ones in the tests conducted at 200 °C. In terms of the effect of temperature, the softer steels were more sensitive to this testing variable, and the harder steels were almost entirely insensitive to the temperature variation. Figure 9 and Figure 10 illustrate the SEM analysis of the wear tracks in the tests at room temperature and 200 °C.

Figure 9 shows the predominance of adhesive wear, in addition to the presence of abrasive and oxidative wear. Figure 10 presents the predominance of adhesive and abrasive wear.

Figure 11 and Figure 12 show the SEM/EDS analyses of the wear tracks, evidencing the presence of oxides in all wear tracks, corroborated by the Raman spectroscopy analysis.

In the wear tracks shown in Figure 11 and Figure 12, the presence of an oxide layer is observed, with a darker contrast in the SEM images and distinct characteristics for the test conditions and hardness, as can be seen through the EDS analyses by mapping O and Fe at the indicated points. An oxide tribolayer formed from oxidized wear debris from the tool steel is the most predominant in the test conditions, with hardnesses of 54 and 57 HRC at a temperature of 200 °C. This finding was also observed by Macêdo et al. [21] in their study. Another condition verified is the presence of Al, probably having been detached from the alumina balls, and this was observed for all tracks tested at room temperature. However, no trace of this element was detected after the tests performed at 200 °C.

Figure 13 presents the Raman spectra for the worn surfaces of WP7V steel.

In Figure 13, bands located at around 221, 287, 390, 504, 604, and 658 cm⁻¹ can be seen, which correspond to the vibrational modes related to hematite (Fe₂O₃), a condition also verified elsewhere [22,23,24,25]. No difference was observed when changing the temperature of the tests.

3.3. Ball Wear Characterization

Figure 14 and Figure 15 show images of the ball wear caps of the samples in the tests at room temperature and at a temperature of 200 °C, respectively.

The largest diameter measured (Figure 14) was for the ball used against DIN 1.2344 steel, and the smallest was that of WP7V steel at 54 HRC. The diameter values follow the same trend as the wear rate behavior for the test conditions at room temperature.

There was practically no variation in the measured diameters of the worn balls after the tests performed at 200 °C, which agrees with the finding of less variation in the wear rates of the tool steels. The transfer of material from the tool steels, represented by the lighter tone of the images, to the respective test ball can also be observed under all conditions studied. There was less transfer in the tests conducted at a temperature of 200 °C, as represented by the greater incidence of dark tones.

Figure 16 and Figure 17 show the SEM/EDS analyses of the worn balls after the room temperature and 200 °C tests, respectively.

In Figure 16, practically all analyzed points contained oxygen, showing that iron oxide was predominant. However, the darker areas indicate the presence of aluminum, and these areas were more intense following the tests with lower-strength tool steels. Conversely, as seen in Figure 17, these darker areas were observed with much more frequency for all tested conditions. These observations will be crucial for describing the role of oxides in the tribological performance of tool steels.

3.4. Discussion

The selection of 200 °C as a temperature for conducting the reciprocating sliding tests was based on the most probable temperature of surface dies during the hot stamping process [26]. However, when reducing a real system to the laboratory scale, it is imperative to consider the possibility of reaching high flash temperatures during laboratory tests. An impressive attempt to reproduce wear mechanisms at high temperatures from the real to the laboratory scale was made by Milan et al. [27]. The researchers found that the oxidative mechanisms were only observable at the laboratory scale if the tests were conducted at room temperature, and it was impossible to induce similar mechanisms when the same hot rolling milling temperature was used in laboratory tests.

Thus, it is very important to check the behaviors of tool steels as a function of the testing temperature. Figure 18 summarizes these effects depending on the hardness level. Both friction and wear decreased when tests were conducted at 200 °C for softer steels. The opposite behavior was observed for harder steels: they were insensitive to the temperature.

An explanation for the behaviors described in Figure 18 can only be made by checking the wear mechanisms. The initial contact depends on the deformation level. It is expected that tool steels will soften at 200 °C. An initial flattening of the alumina balls was observed in all cases during the room temperature tests, becoming more intense when contact was made with softer tool steels (Figure 14). The friction signal for these conditions—softer steels tested at room temperature—was the highest amongst all of the tested conditions, meaning that the friction component of deformation was the highest. Another clue for this initial condition of contact was the presence of aluminum on the wear tracks, originating from the balls.

This high level of deformation is implied in the high level of adhesion of the tool steel to the alumina balls. SEM/EDS analysis confirmed this adhesion from the initial contact steps. Furthermore, these transferred layers were oxidized and mostly composed of hematite (Figure 13). Then, a tribolayer of iron oxide adhered to the aluminum oxide. The continuity of contact gave rise to the partial removal of iron oxide, exposing the alumina ball surface again. For softer steels, the higher level of deformation led to the eggshell effect, facilitating the removal of iron oxide and increasing the wear. The harder steels, with less deformation, were able to keep the iron oxide in contact longer, reducing wear.

The increase in the temperature reduced the initial flattening of the alumina balls. The friction values became lower, resulting in less transfer of debris to the balls. Therefore, all of the steps described for the room temperature tests were less intense, and the level of hardness was not as significant as that observed for the higher temperature tests.

The order of the wear mechanisms is summarized and illustrated in Figure 19 for the tests performed at room temperature, justifying all descriptions made in Figure 18.

A final aspect to consider is the selection of material based on the mechanical properties. Considering the improvement in tribological performance reached with WP7V steel, and maintaining a minimum level of toughness, the hardest condition—57 HRC—is not indicated, as the performance was similar to or worse than at 54 HRC.

4. Conclusions

Considering the tribological behavior of WP7V tool steel with different hardnesses under reciprocating sliding tests, we put forward the following conclusions:

The tribological behavior of tool steels under reciprocating sliding tests depends on the hardness level for tests performed at room temperature.
The friction values in high-temperature tests were not sensitive to the hardness level of the tested steels.
The softer tool steels were more sensitive to the effect of temperature. The higher the temperature, the lower the friction and wear of the tool steels.
To maintain the toughness at a sufficient level, WP7V steel cannot be indicated for use at 57 HRC, since the performance at 54 HRC was similar or even better.

Author Contributions

Conceptualization, G.P. and F.A.; methodology, R.B.; validation, R.B. and G.P.; formal analysis, G.P.; investigation, R.B.; writing—original draft preparation, R.B.; writing—review and editing, G.P. and F.A.; supervision, G.P. and F.A.; project administration, G.P.; funding acquisition, G.P. and F.A. All authors have read and agreed to the published version of the manuscript.

Funding

G. Pintaude acknowledges CNPq through Process 310523/2020-6.

Data Availability Statement

The data supporting the provided results can be available upon request by contacting the corresponding author.

Acknowledgments

The authors would like to thank Metalli Aços Especiais Ltd.a. for donating the tool steels; Angra Tecnologia em Materiais Ltda. for carrying out the heat treatments; Villares Metals S.A. for carrying out the unnotched impact tests; the Multiuser Center for Materials Characterization—CMCM of UTFPR-CT for the scanning electron microscopy and interferometry analysis; the Center for Electron Microscopy—CME of UFPR for the Raman analysis; and C.M. Lepienski for helping with nanoindentation measurements.

Conflicts of Interest

Author Francisco Arieta was employed by the company Tribosystems. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Figure 1. Technical drawing of wear test specimens.

Figure 2. Schematic illustration of the reciprocating wear test setup: (a) sample inside the chamber (opened view); (b) wear track positioning.

Figure 3. Example of a 3D profile of the wear track.

Figure 4. Microstructures of studied tool steels: (a) DIN 1.2344 of 46 HRC; (b) WP7V of 48.5 HRC; (c) WP7V of 54 HRC; (d) WP7V of 57 HRC.

Figure 5. Nanohardness values of studied tool steels.

Figure 6. Fractographies of the unnotched impact test of the tool steels. (a) DIN 1.2344 at 46 HRC; (b) WP7V at 48.5 HRC; (c) WP7V at 54 HRC; (d) WP7V at 57 HRC.

Figure 7. Evolution of coefficient of friction along with testing time: (a) low hardness level; (b) high hardness level.

Figure 8. Average wear rates (mm³/N·m) determined for tool steels under the reciprocating test rigs.

Figure 9. Wear tracks at room temperature: (a) DIN 1.2344 at 46 HRC; (b) WP7V at 48.5 HRC; (c) WP7V at 54 HRC; (d) WP7V at 57 HRC.

Figure 10. Wear tracks at the temperature of 200 °C. (a) DIN 1.2344 at 46 HRC; (b) WP7V at 48.5 HRC; (c) WP7V at 54 HRC; (d) WP7V at 57 HRC.

Figure 11. EDS analysis of wear tracks under room temperature test conditions. (a) DIN 1.2344 at 46 HRC; (b) WP7V at 48.5 HRC; (c) WP7V at 54 HRC; (d) WP7V at 57 HRC.

Figure 12. EDS analysis of wear tracks under test conditions at a temperature of 200 °C. (a) DIN 1.2344 at 46 HRC; (b) WP7V at 48.5 HRC; (c) WP7V at 54 HRC; (d) WP7V at 57 HRC.

Figure 13. Raman shifts in wear-tested samples. (a) Room temperature (RT); (b) 200 °C.

Figure 14. Worn balls from room temperature tests: (a) DIN 1.2344 at 46 HRC; (b) WP7V at 48.5 HRC; (c) WP7V at 54 HRC; (d) WP7V at 57 HRC.

Figure 15. Worn balls from tests at a temperature of 200 °C: (a) DIN 1.2344 at 46 HRC; (b) WP7V at 48.5 HRC; (c) WP7V at 54 HRC; (d) WP7V at 57 HRC.

Figure 16. EDS analysis of worn balls under room temperature tests: (a) DIN 1.2344 at 46 HRC; (b) WP7V at 48.5 HRC; (c) WP7V at 54 HRC; (d) WP7V at 57 HRC.

Figure 17. EDS analysis of worn balls under 200 °C tests: (a) DIN 1.2344 at 46 HRC; (b) WP7V at 48.5 HRC; (c) WP7V at 54 HRC; (d) WP7V at 57 HRC.

Figure 18. Summary of tribological behaviors as a function of test temperature.

Figure 19. Summary of the wear mechanisms for the RT condition. The softer tool steels experienced all steps, while the harder tool steels mainly experienced the two initial ones.

Table 1. Average hardness values from HRC and HV scales, and elastic modulus of metallic matrix (from indentation tests).

Level	Tool Steel	Hardness (HRC)	Microhardness (HV_0.3)	Elastic Modulus (GPa)
Low hardness	1.2344	46.0 ± 0.7	501 ± 7	240 ± 10
Low hardness	WP7V	48.5 ± 0.3	499 ± 10	250 ± 10
High hardness	WP7V	54.0 ± 0.2	599 ± 1	255 ± 8
High hardness	WP7V	56.9 ± 0.2	674 ± 13	250 ± 10

Table 2. Average absorbed energy values of DIN 1.2344 and WP7V tool steels.

Level	Tool Steel	Hardness (HRC)	Unnotched Impact Test
Low hardness	1.2344	46	152 ± 37
Low hardness	WP7V	48.5	58.2 ± 24
High hardness	WP7V	54	45 ± 23
High hardness	WP7V	57	30.5 ± 4.5

Table 3. Average COF values for tests at room temperature and 200 °C.

Level	Tool Steel	RT	200 °C
Low hardness	1.2344	0.601 ± 0.008	0.589 ± 0.009
Low hardness	WP7V	0.62 ± 0.02	0.59 ± 0.01
High hardness	WP7V	0.597 ± 0.006	0.603 ± 0.002
High hardness	WP7V	0.609 ± 0.001	0.589 ± 0.005

Table 4. Average track width values (in mm) for tests at room temperature and 200 °C.

Level	Tool Steel	RT	200 °C
Low hardness	1.2344	1.28 ± 0.03	0.96 ± 0.05
Low hardness	WP7V	1.31 ± 0.01	0.92 ± 0.01
High hardness	WP7V	1.19 ± 0.04	0.880 ± 0.002
High hardness	WP7V	1.18 ± 0.03	0.91 ± 0.01

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MDPI and ACS Style

Breganon, R.; Arieta, F.; Pintaude, G. Sliding Wear Behavior of WP7V Tool Steel with Different Hardnesses Under Reciprocating Test Rig. Lubricants 2024, 12, 453. https://doi.org/10.3390/lubricants12120453

AMA Style

Breganon R, Arieta F, Pintaude G. Sliding Wear Behavior of WP7V Tool Steel with Different Hardnesses Under Reciprocating Test Rig. Lubricants. 2024; 12(12):453. https://doi.org/10.3390/lubricants12120453

Chicago/Turabian Style

Breganon, Rogério, Francisco Arieta, and Giuseppe Pintaude. 2024. "Sliding Wear Behavior of WP7V Tool Steel with Different Hardnesses Under Reciprocating Test Rig" Lubricants 12, no. 12: 453. https://doi.org/10.3390/lubricants12120453

APA Style

Breganon, R., Arieta, F., & Pintaude, G. (2024). Sliding Wear Behavior of WP7V Tool Steel with Different Hardnesses Under Reciprocating Test Rig. Lubricants, 12(12), 453. https://doi.org/10.3390/lubricants12120453

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