PSI - Issue 72

E.A. Gachegova et al. / Procedia Structural Integrity 72 (2025) 260–264

262

Table 1. Chemical composition of Ti64 titanium alloy

Composition V Al

Sn

Zr

Mo

C Si

Cr

Ni

Fe

Cu Nb

Ti

Percent (%)

4.22 5.48 0.063 0.003 0.005 0.369 0.022 0.369 <0.001 0.112 <0.02 0.039 90.0

During processing, the samples were in an upright position, and water flowed over them, which served as a limiting layer. Three materials were used as an absorbing coating: aluminum foil with a thickness of 80 µm, black alkyd paint with a thickness of 50 µm and black PVC tape with a thickness of 100 µm. The main parameters of the laser shock forging are shown in Table 2.

Table 2. Parameters of LSP.

Parameters

Values

Power density

10 GW/cm 2

Geometry of the laser beam spot

Square with 1 mm side

Overlap

0 %

Pulse frequency

5 Hz

Size of the treatment area

30х30 mm

The measurements microhardness were carried out using a METOLAB 502 microhardness tester, Metolab (2025). The series of measurements was carried out in planes parallel to the treated surface in 0.1 mm increments. The distance from the surface for the first series of measurements was 2 diagonals of the print, about 0.05 mm. The pitch along the plane parallel to the surface was 0.2 mm. The load was 10 N. The surface roughness was measured using a NewView 3D optical surface profilometer. The residual stresses were measured by drilling holes using automated system MTS-3000 Restan. This technique consists of drilling a hole with a diameter of 2 mm, which changed the initial state of deformation, contributing to the redistribution of residual stresses that occur in the material during LSP. The current stresses were quantified using a specially configured three-element strain gauge, after which they were used to calculate the residual stresses using specialized EVAL 8 software. The measurement procedure includes the following steps. The strain gauge is attached to the sample using glue. A blind hole is drilled in layers in the geometric center of this sensor. Deformations resulting from the removal of residual stresses are recorded in each layer. Then the residual stresses are calculated using special calculation algorithms, ASTM E837-13a (2013), based on the international standard ASTM E 837. 3. Results Comparing the profiles of residual stresses obtained after processing the samples, two values are usually taken into account: the depth of the compressive RS layer and the maximum amount of compressive stress. In terms of maximum compressive residual stress, the best results were shown by black alkyd paint, with a value along the X-axis reaching - 410 MPa,whilethe highestdepthvalue was achievedwith aluminum foilprocessing. If wetakeall the depthsinto account, we can see that there is not a significant difference in all samples except for aluminum foil in the X axis direction, but we see a significant difference between the maximum values. This is particularly noticeable in the case of PVC tape, where compressive stresses reach -140 MPa. It is also worth noting that the material of the absorbing coating has a significant effect on residual stresses on the sample surface. These residual stresses play an important role in improving the fatigue properties of the material. It can be seen from the profiles that when PVS tape is used and the surface is not coated, the residual stress does not exceed -100 MPa, but with aluminum foil, this value decreases to -180 MPa and with black paint, it increases to -400 MPa. As for the microhardness (Fig. 2), it is worth noting that the material of the absorbing layer has little effect on this parameter. After all the hardening modes, a small positive effect is noticeable, the greatest increase in microhardness was recorded when using PVC tape. It can also be noted that after processing, the depth distribution of this parameter has become more uniform.