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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elements/components, see e.g. Alam et al. (2013) or Malíková et al. (2022). Defects can be both surface ones and internal ones. These include cracks, end craters, porosities, bubbles, inclusions, lack of fusion, spatters etc. They can be caused by many circumstances such as wrong combination of base and additive material, moisture, impurities, poor choice of welding parameters (high welding speed etc.) or other types of non-compliance with correct engineering procedures (insufficient preheating, high carrier gas flow rate, high cooling rates, etc.). Surface defects were indicated by a non-destructive capillary test according to ISO 23277. More extensive internal defects were indicated after a partial surface processing. These defects, which are stress concentrators, could affect the initiation and propagation of fatigue cracks.

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(d) (e) Fig. 4. Detected defects/stress concentrators; (a) surface bubbles and spatters; (b) porosities; (c) seam after connection of two welds; (d) crack; (e) crater 3. Methods for determining selected mechanical parameters The changes of fracture-mechanical properties of a new layer laser cladded on the existing material were tested by microhardness according to Vickers HV0.5, see e.g. Tabor (1951), ASTM E384 or Haušild et al. (2016). Vickers microhardness test is an optical static test of hardness in which the indenter is pressed into the surface of the tested material with a predefined test force, see Fig. 5. The size of indentation (the diagonals) left by the indenter is measured after unloading. The Vickers hardness is calculated from the mean of the impression ’s diagonals (d 1 , d 2 ) and the equation (1). = 1.85 4 ∙ 2 , = 1 + 2 2 where – test force [kgf], d – average (avg) diagonal length [mm] (1) Three tests of microhardness for each type of surface layer were carried out and processed. During the tests, two sets of microhardness measurements were performed on each sample. The one representative result for each of them is stated in this work. Modifications of values of Young ’ s modulus in the vicinity of the interface and in dependence on the distance from the starting point of measurement, have been calculated based on the course of measured microhardness. Further information about the issue above is described in more detail in a previous study by the authors of this work Doubek et al. (2022). In this paper, only the results are stated.