PSI - Issue 43

Miroslav Polášek et al. / Procedia Structural Integrity 43 (2023) 306–311 Author name / Structural Integrity Procedia 00 (2022) 000 – 000

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2. Experimental Work 2.1. Experimental Material X37CrMoV5-1

The basic types of materials used in these experiments were two types of low and medium alloy steels. The first material is a typical example of the production of small calibre 42CrMo4 barrels. It is chrome-molybdenum steel. This steel or its equivalents are used all over the world as a steel to produce heavily stressed barrels. The second material is medium alloy steel 30CrNiMo8. It is a steel used for highly stressed components in the engineering industry. It contains 0.32% of carbon, which is less than the first steel, but contains a higher percentage of other alloying elements. In addition to the same amount of silicon and almost the same amount of manganese, it contains more chromium and molybdenum. In addition to the first steel, nickel contains up to 2.2% of the EN ISO standard. We have chosen the second material as a potentially new material for the production of highly stressed barrels, because it meets all the criteria and requirements for barrel steel, while still being acceptably machinable with its strength and hardness. The experimental material was supplied in the form of a rod with a diameter of 50 mm and a length of 1000 mm. In addition to tests, we also produced a semi-finished product from this material for the production of mainly .50BMG calibre The chemical composition of the samples was verified by a Q4 TASMAN spectrum analyser and are shown in Table 1. A comparison of the mechanical and physical properties of each experimental steel is given in Table 2. Table 1. Chemical composition of experimental steels (wt.%) and basic mechanical and physical properties of steel X37CrMoV5-1 42CrMo4 C Si Mn Cr Mo Ni min - max 0.38 – 0.45 max 0.40 0.60 – 0.90 0.90 – 1.20 0.15 – 0.30 - Spectral analysis 0.41 0.23 0.77 1.07 0.15 - 30CrNiMo8 C Si Mn Cr Mo Ni min - max 0.26 – 0.34 max 0.40 0.50 – 0.80 1.80 – 2.20 0.30 – 0.50 1.80 – 2.20 Spectral analysis 0.32 0.22 0.54 2.11 0.37 1.98

Table 2. Comparison of basic mechanical and physical properties of experimental steels Hardness

Tensile Strength [MPa]

Yield Strength [MPa]

Elongation A5 [%]

ISO-V Energy of impact [J]

Contraction Z [%]

HV5 (QT)

42CrMo4 30CrNiMo8

298 389

986 1251

814 1158

13 15

54 60

63 57

2.2. Dry Sliding test Wear tests were performed using the UMT TriboLab high-speed rotary module (Figure 2). The configuration of the UMT TriboLab device was set to the ball-on-disc measurement method using one kind of pressing material (Krbaťa et al. 2019). This material was the bearing ball G40, which is used in bearings, with a diameter of 4.76 mm. Rotary tribometric tests were performed at a load of 2.5 N. The G40 bearing ball was firmly clamped in the holder and performed a rotary movement over diameters of 22, 26, 30, 34, 38 mm. Samples of experimental steels were made in the shape of a disk with a diameter of 50 mm and a thickness of 10 mm. All measurements were performed in a room with a stable room temperature of 22 °C (Drozd et al. 2020). Friction coefficients were recorded continuously during the test. The volume loss of the test material was calculated by multiplying the length of the slip path by the cross section of the worn area. The UMT Tribolab automatically calculates and records the coefficient of friction (COF) using electrical sensors using the ratio of normal force and horizontal friction force (Gao et al. 2019, Yuan et al. 2019).