*2.3. Heat Treatments*

Specimens (100 mm × 20 mm) were taken from the clad plate and heat-treated at laboratory scale by means of an FM77H (chamber size 250 mm × 190 mm × 500 mm) muffle able to maintain 20 ◦C difference for 2 h. The effect of final heat-treatment conditions on the properties of both the welded layer and substrate were investigated by performing stress-relieving treatments on specimens taken from the clad plate. The original specimens were also fully retreated to simulate a Q and T treatment after cladding of the as-rolled plates. The heat-treated samples were examined in terms of microstructure and hardness indentation profiles. The following cases were considered (temperatures and holding times are indicated) (Table 3).


**Table 3.** Heat treatment conditions on the performed tests.

The 640–660 ◦C stress-relieving temperature range was chosen high enough (higher than the standard one for such class of material) to investigate its effect on the eventual hardness of peaks at the interface. Three different fully Q and T cycles (including austenitization step) were chosen to simulate the possibility of cladding the as-rolled plate before submitting it to a Q and T treatment.

### *2.4. Chemical Composition by X-ray Fluorescence (XRF)*

In order to have a more quantitative assessment of the iron content in the cladding material, a through-thickness profile was measured by X-ray fluorescence (XRF), starting from the second pass layer and moving towards the base steel on 30 mm × 20 mm specimens. Because a flat surface was required for the analysis, a section perpendicular to the plate was prepared by grinding the first 0.5 mm layer at the external clad surface. After performing the chemical analysis, the other 0.5 mm was ground and a chemical analysis carried out again. This procedure was repeated for a total depth of 3.5 mm.
