PSI - Issue 42

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

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In Fig. 8, the dependences of the tensile strength on the microhardness HV0.5 (arithmetic mean of the measurement values of microhardness Set 1 and Set 2) when passing through the interface between the cladded layers and the steel substrate are plotted.

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Fig. 8. The course of the dependence of the tensile strength on the hardness HV0.5; red - aluminium bronze Metco 51NS; blue - hard chrome Rockit 401 Based on the submitted information and results plotted in the tables and figures above, the following statements can be summarized: • Regarding to metallographic analysis by an electron microscope, no microscopic defects were observed in the analysed samples. However, as can be seen in Fig. 3, there is a partial mixing of molten material with different mechanical properties in the bi-material interphase zone. These inhomogeneities can lead to initiation of microcracks and the subsequent propagation of microstructural short cracks. • According to the analysis for identifying the real chemical composition of the cladded layers by XRF spectrometry, the chemical composition of the cladded layers corresponds sufficiently with the declared composition of the used cladding powders. Nevertheless, for all analysed aluminium bronze coatings, an increased content of aluminium (approximately 13 - 16%) was detected. • Over the course of a non-destructive capillary test and after visual inspections of the partially machined surfaces, both the surface and the internal defects were identified in some parts of the coating. An increased risk of initiation and spreading of potential fatigue cracks, which should be assessed via the usual methods during the next phase of the research, was expected. • For aluminium bronze (Metco 51NS) in a combination with S960 substrate, there is a gradual increase in tensile strength due to the structural changes and growth of microhardness near the bi-material interface. In the area of the transit zone (approx. 2.2 – 2.4 from the starting point), a sharp rise in the tensile strength is evident, followed by a passage through HAZ and a stabilization with the values common for the high strength steel S960 (which is stated in the range of 980 - 1150 N/mm 2 ). • For hard chrome (Rockit 401) in a combination with S960 substrate, due to the structural changes and the decrease in microhardness towards the bi-material interface, there is also a gradual decrease in the tensile strength. As with aluminium bronze, there is a significant transit zone for hard chrome (visible between 1.6 and 2.0 mm from the starting point) followed by the stabilization with the nominal S960 values. • As can be seen from the graphs in Fig. 8, the dependence between the measured hardness HV0.5 and the normatively determined tensile strength is almost linear. 5. Conclusion As a part of the experimental campaign, test samples have been created. High strength steel S960 was used as the base material and a layer of the additional material (aluminium bronze and hard chrome have been selected) was deposited on this substrate by laser cladding technology. The bi-material interface created in this way was subjected