**1.1 Background**

Depending on the melting method of the coating material, the thermal spraying processes can be classified into four main categories, as presented in **Figure 1**.

The thermal spraying processes are realized with the help of installations and equipment capable to develop the necessary heat for the CM melting, to achieve the dispersion of the formed droplets into fine particles and to transfer to them kinetic energy.

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**Figure 2.**

*Hard Alloys with High Content of WC and TiC—Deposited by Arc Spraying Process*

The substrate material can be of any nature: ferrous, non-ferrous, plastic, ceramic, textile, glass, wood, but the coating material is limited by its capacity to be transformed into a liquid state, or to be processed into of powder, wire, cord or wand, [12–13]. Usually, spraying processes allow the deposition of a diverse range of materials: pure metals and metal alloys, cermets, ceramics and under certain

The thermal spraying methods, recognized in the specialized technical literature

• production of new layers, with physical, chemical, mechanical and technologi-

• obtaining pulverulent products used in different industrial sectors (sintering,

Recognized as the cheapest process for obtaining spray coatings, two-wire arc spraying finds numerous industrial applications that aim to obtain both surfaces

The spraying method consists of making an electric arc between two consumable

• the wire entrainment device, also called the wire feed mechanism - according

• melting-spraying module, known as "spray head" - according with SR EN

metal wires, followed by the atomization of the molten material with the help of a compressed air jet and the spraying of those particles on the substrate surface - **Figure 2**, [17]. Although the functional principle constructive of electric arc spraying devices is apparently simple, it must to allow the correlation between the wire feed speed, the intensity of the electric current in the circuit and the pressure of the compressed air, in the purpose of obtaining qualitative coatings and maximum yield, [11]. The electric arc coating devices also called spraying guns, are powered by direct current generators which have a rigid characteristic, develop voltages between 25 and 45 V and high currents with values in the range of 100–500 A, [18]. They are

*DOI: http://dx.doi.org/10.5772/intechopen.94605*

as synergetic and versatile [16], have as objectives:

characterized by a modulated design, composed of:

with SR EN 657/1995 standard;

*Schematic representation of electric arc coating method, [17].*

657/1995 standard.

cal properties different from those of the substrate;

• restoring the geometry of some parts with a high wear degree;

with new properties and the restoration of used surfaces. [11–13].

conditions polymers, [2, 14, 15].

spraying).

**Figure 1.** *Classification of thermal spray methods, [11].*
