## 3 Results and Discussion
### Mixing Behavior in Laser-Arc Hybrid Test Welds
Mixing at the weld surface portion of the weld displays the opposite behaviour with slightly better mixing for leading wire feeding. The mixing results from EDS stepwise characterization show the same trend. Average filler metal mixing values in the weld root portion (ML4) of test weld LAH4 (trailing wire feeding) and LAH3 (leading wire feeding) are 46% and 39.5%, respectively (Figure 10). At the weld surface part (ML1), corresponding average values are 37.5% and 46.8%, respectively. If the mixing profiles in Figures 11d and 12d are examined, it can be noticed that the mixing profile at the measurement line 4 (ML4) is smoother in LAH4 than in LAH3. The majority of mixing %-values of ML4 of weld LAH4 are between \(\sim\)45% and 50%, whereas in weld LAH3 mixing %-values show greater fluctuation and are between \(\sim\)35% and 45%. The mixing at the weld surface part (upper half) seems, however, to be more homogenous in weld LAH3, which was made with leading wire feeding, than weld LAH4, made with trailing wire feeding. When the mixing profiles of ML2 near the weld surface in Figures 11b and 12b are compared, it can be seen that the mixing profile is smoother and shows less variation in weld LAH3 than weld LAH4. Trailing wire feeding with the laser-arc hybrid process melts more base metal than leading wire feeding (see Table 4) and the observation of less homogenously distributed filler metal in the weld surface part of the weld with trailing wire feeding can be partly attributed to the higher local base metal dilution at the weld surface part of the weld. In Figure 9d, a wedge-shaped fusion area can be seen near the weld surface. The inside area and tip of the wedge contain spots of green and yellowish colours indicating chromium content levels of the base metal. Figure 10: Average values of filler metal mixing-% from the data of measurement lines ML1–ML4 in laser-arc hybrid test welds. When laser-arc hybrid welds were produced in single-pass V-groove configuration, average filler metal mixing values of measurement lines ML1 to ML4 had the highest mixing values of the laser-arc hybrid test welds. From Figure 10, it can be seen that in weld LAH5, which was made using leading wire feeding, the average filler metal mixing values are \(\sim\)46% at the bottom part of the groove area (ML3 and ML4) and \(\sim\)54% at the surface part (ML1 and ML2). The test weld LAH6, which was made using trailing wire feeding, shows \(\sim\)56% average mixing level values at one third thickness of the joint (ML2) and when measuring deeper in the joint at ML3 and ML4, average values were \(\sim\)53% and 50%, respectively. When examining Figure 9e and particularly Figure 9f, it can be noticed that chromium as regards weight-% is not homogenously distributed in the mid-section area of both weld LAH5 and LAH6. [PERSON] and orange colours indicating high chromium weight-% levels can be clearly seen near the fusion lines at the mid-thickness range of both welds. The filler metal mixing profiles of weld LAH5 and LAH6 in Figures 13 and 14 support the above observation. Large spikes can be seen in the mixing profiles of Figure 13b,c and Figure 14b,c with high local values of 60-75% in the mid-thickness area of weld cross-sections LAH5 and LAH6. In addition, it can be seen that test weld LAH6 has similar mixing behaviour near the weld surface as earlier described in test weld LAH4. Both weld LAH6 and LAH4 were produced using trailing wire feeding. Figure 11: Filler metal mixing results from EDS stepwise characterization. (**a–d**) Filler metal mixing-% profiles of measurement lines 1–4 (ML1–ML4) from test weld LAH3 (**e**). In figures (**a–d**) one step between adjacent measurement points in the horizontal axis equals 100 micrometres. Figure 12: Filler metal mixing results from EDS stepwise characterization. (**a–d**) Filler metal mixing-% profiles of measurement lines 1–4 (ML1–ML4) from test weld LAH4 (**e**). In figures (**a–d**) one step between adjacent measurement points in the horizontal axis equals 100 micrometres.