**2. The evaluation of blasted surfaces roughness**

Functional properties of areas are dependent on the various surface properties and subsurface layers of a base substrate. One of the criteria concerning the quality of products in terms of production genesis is their geometric and dimensional accuracy, then the surface quality, particularly its roughness. The ISO plan was created for such a purpose creating the structure of necessary norms and standards for the area of "Geometrical specification of products."

From the point of view of a component function, geometrical properties of a surface are very important in many cases (e.g., in conditions of friction and wear). Therefore, it is necessary to put a sufficient emphasis on the evaluation of surfaces geometry and the determination of profile deviations from the defined plain [10–13].

The experimental analysis used various blasting materials [5]:


The type of material whose surface has been subjected to the surface roughness analysis was the steel plate S235JRG2 (EN 10025), thickness 2 mm. It is a non-alloy high-quality structural steel, it can be cold formed and after subsequent normalization even in heat, it is suitable for welding. Chemical composition: C – 0.19% max, Mn – 1.50% max, P – 0.045% max, S – 0.045% max, N – 0.014% max. The dimensions of the testing samples were 100 × 30 mm.

The blasting was pneumatic air-blast device by equipment TJVP 320, producer Škoda, Plzeň, Czech Republic. The samples were blasted with abrasives at working pressure of 0.6 MPa, nozzle diameter was 1.2 mm, blasting angle 75° and the distance of the nozzle from the substrate was 200 mm.
