## 3 Evaluation of Experimental Results
### Micrographic Examinations  
These are detailed investigations that allow for the assessment of the quality of the deposited layers and provide indications for optimizing the hardfacing welding process. The microstructure of the solution heat treatment of the base metal was assessed by quantitative metallographic determinations with a Fischer feritscope (DMP 30 equipment from Berg Engineering & Sales Company, Inc., Rolling Meadows, IL, USA) and is composed of approximately 48% ferrite and 52% austenite (Figure 3). In Figure 4, the microscopic image of the deposited metal-base metal interface during the deposition of a single layer is rendered. As a result of the melting of the filler material and a small portion of the substrate material, a weld bath is formed. The solidification process ensures good bonding between the two materials, and defects such as pores and cracks are absent. In the lower part of the deposited material (towards the base material, BM), a dendritic microstructure oriented strongly in the direction of the thermal gradient appears, a phenomenon explainable by the rapid cooling rate from the high temperature reached during welding. The development of crystalline grains in the melted zone from pre-existing grains is called epitaxial growth. During pulsed current welding, the heat input into the samples is lower than in conventional electric arc welding, and the cooling rate is increased. Consequently, the proportion of carbides precipitated in the interface zone, a phenomenon due to the diffusion tendency of carbon from the deposited material (DM) to the base material, is limited. It is known that if the cooling rate from the peak temperature reached during welding is higher, the degree of undercooling is higher, the critical radius of crystallization nuclei is smaller, the number of nuclei is higher, and the resulting structure is finer. Figure 2: Macrographic images of the layer—substrate system: (**a**) one layer deposited; (**b**) two layers deposited; (**c**) three layers deposited. As solidification progresses, the upper part of the coating develops a cellular-dendritic microstructure in which the presence of secondary phases can be observed (see Figure 5). Figure 4: Micrograph of the MD–MB interface at the deposition of the first layer. Figure 3: The microstructure of the base metal. The phenomena of precipitation of secondary phases such as carbides are somewhat less intense because a significant portion of the heat generated during welding is absorbed by the water in which the majority of the base metal mass was placed. The presented microstructural images characterize the weld-deposited metal layers without subsequent hammering applied for internal stress relaxation. It has been previously shown that the primary characteristic of the deposited metal from this steel is its high sensitivity to work hardening. If correct surface hammering is carried out after the deposition of each layer (under the instructions provided in Figure 6), significant increases in hardness and important modifications in the microstructural features will be observed. To avoid the danger of cracking in deposited layers under the action of internal stresses, it is always recommended to reduce them by surface hammering. Under the action of local deformations, stress relaxation occurs, thus reducing the risk of cracking. Figure 5: Micrograph of the outer layer deposited by hardfacing welding. Figure 6: Modes of hammering the deposited layer. Figure 6 presents an example of internal stress relaxation through hammering, applied incorrectly on the left and correctly on the right. The operation involves delivering blows with constant amplitudes, at the same frequency (2-3 Hz), as well as maintaining constant and uninterrupted paths. The deformation time was 4 min with continuous and uniform movement of the chisel over the entire surface, alternating the hammering direction at a 90-degree angle after each pass.