**1. Introduction**

Nickel-based alloys are widely used in various areas of industry, such as chemical, petrochemical, nuclear reactors, warfare, aerospace, food processing devices, and steel production facilities, due to an association of high mechanical strength, good corrosion resistance, and weldability. The performance of these alloys is associated with the face-centered cubic structure of the matrix, which can be hardened by solid solution or by precipitation of intermetallic compounds [1].

There are several hard-facing alloys, the most common of which are Fe-based, Co-based, and Ni-based. Co-based hard alloys have many applications, but they become radioactive in nuclear environments, and this phenomenon has restricted the use of Co-based coatings for high-temperature applications. To minimize workers'

exposure to Co60 radiation during handling and maintenance operations, nickelbased hard-facing alloys from the NiCrSiBC family were developed. Colmonoy alloys (NiCrSiBC) have a wide variety of compositions and this consequently makes their use very abundant. It can be said that currently alloys are used preferentially for coating materials [2, 3].

It can be said that Ni-based hard-facing alloys, which still have carbides and borides in their structure formed from alloying elements, are popularly used as coating materials. Among the hard Ni-based alloys, colmonoy can be highlighted, which is widely used, and may also have different NiCrSiBC compositions depending on the alloying elements [4, 5].

Alloys from the NiCrSiBC family, such as colmonoy, have as their main characteristic their high resistance to wear and corrosion at high temperatures. These alloys were basically developed for deposition using some welding processes. Due to their excellent characteristics and lower cost compared to Co superalloys, Ni-based alloys have been deposited by various welding processes, such as plasma transferred arc (PTA), tungsten inert gas (TIG) and laser cladding [6–8].

The strength of colmonoy alloys (NiCrSiBC) can be increased by the formation of precipitates such as borides and carbides. Some studies of the alloys of the NiCrSiBC family deposited by laser cladding on a steel substrate showed the presence predominantly of the intermediate phases formed, in the form of carbides, borides, and silicides: CrB, Cr5B3, Ni4B3, Cr5B3, Cr7C3, and Ni3Si [9, 10].

Although welding deposition processes are widely used and applied, the substrate, which is usually stainless steel, has a high iron content, which can change the composition of the coating, causing the phenomenon known as dilution. The alloys of the NiCrSiBC family are very sensitive to the presence of the iron element, which results in a change in their microstructure and consequently in some mechanical properties, as observed in the works [9, 11, 12].

It should be noted that pulsed plasma sintering (SPS) can also be a processing route for nickel-based alloys, although still little explored, as mentioned in the work by [13]. In addition, there are no reports that clearly show the study of the influence of Fe on SPS-processed Ni-based alloys.

Spark plasma sintering is considered a powder metallurgy technique that features fast manufacturing routes at relatively low temperatures, involving simultaneous applications of pressure and temperature, resulting in engineering components with relatively high density and good mechanical properties, compared to others. Conventional sintering methods [14].

SPS technique stands out for its ease of operation and precision in sintering energy control, high sintering speeds, safety, and reliability [15].

Spark plasma sintering involves the simultaneous application of load as well as heat on the materials to be sintered. SPS is a new method meant for consolidation of nano-structured materials with hindered grain growth, efficient shrinkage in less time, and cleaner grain boundaries for effective interface formation. This technique utilizes high-temperature spark plasma generated by discharging exactly at the gaps of powder particles with an on-off electrical current. At the initial stage of the SPS process, the generated spark plasma induces neck formation and thermal diffusion process on the particles to be sintered. An electric field formed by DC current can also facilitate thermal diffusion process. Therefore, the SPS process involves the densification of poorly sinterable materials at a very short interval of time and at low temperature when compared with the conventional sintering process [16].

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

Colmonoy alloy properties are strongly related to the microstructure formed after alloy processing. Thus, in this work, greater attention was given to the correlation of the microstructural aspect and some important properties, such as density and hardness of colmonoy alloy, sintered by SPS, maintaining the parameters determined in the work of [5].

Currently, it can be said that there are few published works that report microstructural aspects of SPS-sintered NiCrSiBC alloys. Thus, the current literature basically brings studies of these alloys deposited on steel substrates, which often analyze the effect of Fe dilution on the microstructure of the alloy [17]. In this way, this work intends to show that it is possible to sinter the colmonoy alloy by the spark plasma sintering (SPS) process, and consequently contribute to future studies on the possibility of sintering the colmonoy alloy on a stainless-steel substrate.
