## 3 Results  
The chemical composition was determined for the feedstock powder, as well as the coating in the as-clad state, the as-ground state, and both borided states by XRF spectrometry. Five measurements were conducted for each state. The normalized values of the main alloying elements are shown in Table 4.  
The results of the XRF measurement reveal a good correlation between the chemical composition of the Inconel 718 powder feedstock and the coating system. This consistency, which was already achieved in the as-clad state, confirms the process quality. The results could be confirmed in the polished condition. XRF measurements within GDOS calottes demonstrated an excellent agreement of the chemical composition to the polished state. This confirmed a homogeneous chemical composition without elemental gradations over almost the entire coating thickness. Consequently, mixing between the substrate and coating material, as well as the vaporization of constituents, was largely prevented. Due to diffusion enrichment with boron, the ratios of the alloying elements in the immediate surface area shifted in relation to each other. Nickel increased significantly with the increasing treatment time compared to chromium and iron. The average thickness of the coating was approximately 500 \(\upmu\)m. After mechanical finishing, the thickness was reduced to about 230 \(\upmu\)m. The transition zone was crack-free and ensured good metallurgical bonding. Limited intermixing appeared only within the immediate interfacial area. After laser cladding, thermochemical boriding treatments were carried out. Figure 1a,b shows exemplary SEM images of the coating after boriding using backscattered electron imaging. Despite the deviation from the intended composition, a homogeneous precipitation layer formed for both states. The thickness of the boride layer after a treatment of 2 h is at least 22 \(\upmu\)m. No cracks, pores, or other structural defects were visible. The smooth transition from the boride layer to the Inconel 718 cladding ensured strong adhesion between the two layers. Thermochemical diffusion coatings often provide better adhesion with the substrate compared to faster coating application techniques, such as thermal spray coating [45]. At an increased boring duration of 8 h, an increase in diffusion depth to almost 65 \(\upmu\)m was observed. Additionally, irregularities were detected on the surface, which increased with the duration of the boriding treatment. Three areas could be distinguished in the cross-sectional microstructures. The topmost double-phase boride layer displayed a homogeneous structure. The diffusion zone underneath the boride layer exhibited an irregular morphology and contained grain-boundary precipitates. The precipitates extended far along the grain boundaries until they reached the core of the Inconel 718 cladding, which was unaffected by the diffusion of the boron. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sample** & **Ni** & **Cr** & **Fe** & **Nb** & **Mo** & **Ti** \\ \hline feedstock powder & 53.1 & 19.1 & 18.5 & 5.1 & 3.3 & 0.9 \\ coating (as-clad) & 53.4 & 19.5 & 19.0 & 4.4 & 2.7 & 1.0 \\ coating (polished) & 53.8 & 19.0 & 18.9 & 4.5 & 3.0 & 0.8 \\ coating borided 2 h & 58.4 & 15.5 & 18.1 & 4.4 & 2.9 & 0.6 \\ coating borided 8 h & 68.0 & 9.7 & 15.2 & 4.2 & 2.7 & 0.2 \\ coating 50 \(\upmu\)m above substrate & 53.8 & 19.1 & 18.9 & 4.6 & 2.7 & 0.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Chemical composition measured by XRF, in wt%. In order to identify the elemental distribution within the boride layer and the diffusion zone, GDOS measurements were carried out. The results of the qualitative analyses are shown in Figure 2. Depending on boriding time, a constant plateau for boron intensity was observed, which is characteristic of the boride layer. Beyond a certain depth, the boron intensity decreased abruptly. This corresponded to the diffusion zone containing the precipitates as detected in the SEM.