# Advantages of Corrosion-Resistant Overlay Welding on Steel S355J2N
## 5 Discussion  
Based on the data from the EDX analysis performed with the electron microscope, the following conclusions can be drawn for the buffer layer weld. * Average alloy content: Cr 18.67%; Ni 10.27%; Mo 2.82%; Mn 2.11%; Si 0.41%. * Average alloy content in the austenite: Cr 17.64%; Ni 12.38%; Mo 2.25%; Mn 2.23%; Si 0.39%. * Average alloy content in the delta ferrite: Cr 19.7%; Ni 8.17%; Mo 3.395%; Mn 1.985%; Si 0.435%. * Measured Cr/Ni ratio in the weld: 1.818. * PREN value: 27.98. It can also be concluded that, in the first weld, the Cr content in the austenite is 2.06% lower than in the delta ferrite. At the same time, the Ni content in the delta ferrite is 4.21% lower than in the austenite. The driving force behind these distribution differences lies in the solubility laws, dependent on the microstructure. These key enrichment differences determine the distribution of other elements, particularly Mo, in the austenite and delta ferrite. Further analysis of the data in Table 3 for the two-layer overlay and their fusion zones leads to the following conclusions:  
* Average alloy content: Cr 19.63%; Ni 10.78%; Mo 3.13%; Mn 1.85%; Si 0.50%. * Average alloy content in the austenite: Cr 17.80%; Ni 12.90%; Mo 2.53%; Mn 1.90%; Si 0.51%. * Average alloy content in the delta ferrite: Cr 21.45%; Ni 8.66%; Mo 3.73%; Mn 1.80%; Si 0.50%. * Measured Cr/Ni ratio in the weld: 1.821. * PREN value: 29.96. It can also be concluded that, in the overlay welds, the Cr content in the austenite is 3.65% lower than in the delta ferrite. This difference has approximately doubled. This was caused by the accumulation of Cr in the delta ferrite, which diffused from the buffer layer towards the overlay due to the sufficiently long cooling time and high temperature. At the same time, the Ni content in the delta ferrite is 4.24% lower than in the austenite, which is virtually identical to the value measured in the buffer layer. The lack of change can be explained by the higher diffusion activation energy required for nickel compared to chromium [36]. No significant changes in the quantities and ratios of other key alloying elements can be observed compared to those seen in the buffer layer. Further conclusions can be drawn by examining the total thickness of the deposited layers. Based on the data in Table 3, the nickel content is lowest in WM3 \(\delta\)-ferrite 1, at 7.19%, which still ensures an austenitic microstructure [35; 37]. * Average alloy content considering the total (buffer layer + cladding layers) layer thickness: Cr 19.42%; Ni 10.67%; Mo 3.02%; Mn 1.90%; Si 0.48%. * Measured Cr/Ni ratio characteristic of the deposited total layer: 1.82, which indicates a stable, uniform Cr/Ni distribution. * Characteristic PREN value of the total layer: 29.386. This value shows a good match with the value typical for the 317L stainless steel family [38]. The uniform microstructure of the overlay weld (Figure 9) allows the establishment of a linear relationship between the Cr(E) equivalent values and the measured Cr(R) contents. The examination takes place separately in case of the buffer layer and complex cladding layers. The ratio pairs are as follows:  
* Schaeffler (2): \(\mathrm{Cr_{(ES)}/Cr_{(R)}=1.133}\). * WRC-92 (3): \(\mathrm{Cr_{(EW)}/Cr_{(R)}=1.083}\). In the buffer layer (WM1): \[Cr_{(R)}=\frac{21.13_{(ES)}}{1.133}=18.649\to 18.65\%;\;Cr_{(R)}=\frac{20.224_{(EW)}}{1.083}=18.674 \to 18.67\%\] (5) In the cladding layers (WM2-WM3 + fusion zones): \[Cr_{(R)}=\frac{22.26_{(ES)}}{1.133}=19.647\to 19.65\%;\;Cr_{(R)}=\frac{21.26_{(EW)}}{1.083}=19.63 1\to 19.63\%\] (6)  
The results show small deviations regarding the individual layers. The buffer layer already has a sufficiently high PREN value, and the measured Cr content significantly exceeds the first resistance level. Therefore, considering the minimum required layer thickness, the buffer layer could also serve as the overlay layer.