**2. Methodology**

Commercial powders of Colmonoy-5 alloy (Ni-14Cr-3Si-2.5B-0.6C-4,2Fe) produced by the manufacturer WallColmonoy Corporation were used to process the samples. Powders were produced by atomization technique. The atomization process consists of casting system, which performs the fusion raw material for one induction oven under controlled environment where alloys are smelted, refined, and degassed. Refined melt metal is poured through a system crucible in a gas nozzle, where the stream of the melted metal beam is disintegrated from the kinetic energy of high-pressure inert gas flow (Argon). **Figure 1** shows a schematic of the gas atomization technique [18].

The average particle size of the powders was provided by the manufacturer. To analyze the morphology of the powders, images were made via confocal microscopy.

Colmonoy-5 alloys were sintered by spark plasma sintering (SPS) technique, maintaining technological parameters predetermined in the work [5]. SPS sintering occurred at 900°C under 50 MPa for 15 minutes.

The sintered material was subsequently characterized under structural aspects, microstructural, relative density, and Vickers hardness. **Figure 2** shows the general and succinct roadmap of the main stages of the development of the work.

In order to evaluate sintering effectiveness, the densification alloy after sintering was measured. For that, the density (apparent specific gravity) was determined using the Archimedes method, using four samples. The calculation of the apparent specific mass is based on the value of the dry mass of the sintered (MS), the mass of the same immersed in water (MI), and the saturated mass (MA) that is obtained after the sample is boiled for a period of 20 minutes. For this, the density of water is also considered, as shown in eq. 1. The percentage of densification (relative density) was calculated from the values of the experimental density of the sintered material and the theoretical density (eq. 2), that is, it is the ratio between the ASG of the sample and theoretical alloy density of 8,14 g/cm3 [4].

$$\text{ASG} = \frac{\text{MS}}{\left(\text{MA} - \text{MI}\right)} \times \rho\_{\text{H2O}} \tag{1}$$

$$Density(\%) = \frac{ASG}{Density \text{ Theoretical}} \times 100 \tag{2}$$

**Figure 1.** *Gas atomization process [18].*

The microstructural aspect of the sintered body after SPS was performed from SEM. Before SEM analysis, the samples were metallographically prepared, first sanded (100 to 1200 mesh), and later polished and subjected to chemical attack. Phase identification was performed through X-ray diffraction analysis, using a Bruker D2 phaser diffractometer. The diffractometer is equipped with a Cu-Kα radiation tube, where the samples were scanned in the 2θ range, with an interval between 20° and 90°, under a step of 0.05° for 3 seconds. The characteristic peaks in the diffractions obtained were analyzed, and the results were compared with the ICDD (International Center Diffraction Data) database, to help identify the phases present.

Vickers hardness tests were carried out with the aid of a digital micro hardness tester DHT, HVS – 1000, performing five indentations [19, 20] in each sample and applying a load of 1 kgf in the tests for a time of 10 seconds.

*Spark Plasma Sintering of NiCrSiBC Alloys DOI: http://dx.doi.org/10.5772/intechopen.108597*

#### **Figure 2.**

*Processing route, characterization steps, and testing of Colmonoy-5 alloy.*

**Figure 3.** *Colmonoy-5 alloy powders with spherical morphology.*
