PSI - Issue 42

Pavel Doubek et al. / Procedia Structural Integrity 42 (2022) 1529–1536 Pavet Doubek et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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(2015), Bhat et al. (2019), than linear elastic theory about behavior of crack in the vicinity of bi-material interface cold be found in e.g. Náhlík et al. (2011), Sevcik et al. (2012), Malíková & Klusák (2018), Klusák & Krepl (2018), Krepl & Klusák (2019). An innovative technology in this field is laser cladding, see e.g., Zhu et al. (2021). In this method, the metal powder is fed to a laser beam, where it is melted together with the base material and required surface layer is then formed. A strong metallurgical bond is formed between the coating and the base material, see Fig. 1. The advantage of this technology is low temperature impact on the cladded parts, small heat affected zone (hereinafter the HAZ), precise distribution of the laser energy to the desired locations, excellent adhesion and cohesion of coating, wide range of possible material combinations and high efficiency, see e.g., Lasertherm or Brueckner et al. (2017). The application of various coatings to the substrate may cause a change of the properties, residual stresses and initiate a potential formation of surface concentrators. Samples of different material combinations were created with intention to describe the effect of structural changes near the bi-material interface on the fracture mechanical properties during an experimental campaign. These investigations are an initial part of intended upcoming research in the field of laser-cladded metal layers.

(a) (b) Fig. 1. Laser cladding (a) an example of preparation of the bi-material interface made by the laser cladded protective layer on structural steel and (b) an example of the detail of an interface between S960 and aluminium bronze 2. Materials and detection of stress concentrators in laser cladded layers High strength steel S960 has been used as the base material. This kind of steel is a frequently used material for the production of structural elements due to its advantageous strength-to-weight ratio and additionally, it has a sufficient weldability with an excellent toughness and strength in the HAZ, see e.g. Guo et al. (2016). Aluminium bronze Metco 51NS and hard chrome Rockit 401 have been chosen as additional materials. Layers of cladded material were deposited on the base material by using laser cladding technology in a direction of rolling of the base material. The parameters of the selected materials are given in Tab. 1. Various parameters of laser cladding technology (size of the layer, temperature, feed rate, powder ratio, carrier gas velocity and flow rate) were modified during the process. Specimens were subsequently machined to dimensions 5.5 × 21 × 100 mm and the thickness of the cladded layer fluctuated in the range of 0.6 - 1 mm. By this approach, we resulted a wide range of samples with different structure and properties, see Fig. 2.

Table 1. Material of the substrate, laser-cladded layer and its parameters Designation Description E [GPa] ν [-]

Hardness

Type

S960

High Strength Steel Aluminium bronze

202 117 104

0.27 0.32 0.22

346 158 620

substrate

Metco 51NS Rockit 401

laser-cladded layer laser-cladded layer

Hard chrome