**2.1 2D surface roughness parameters and characteristics of blasting surface**

The basis of measurement 2D surface roughness parameters and characteristics of surface – the planer evaluation (in direction x – y) is a unit of length (μm). ISO 4287:1997 standard – nowadays the valid international standard defines terms and surface roughness parameters. In this standard, the calculating system for the evaluation of surface roughness parameters is based on the system of the mean line of the roughness profile, the waviness, and the mean line of the primary profile.

2D roughness measurement is often performed using a contact profilometer Surftest SJ – 301, Mitutoyo, Tokyo, Japan. Settings in roughness measurement:


*Surface Characterization after Blasting DOI: http://dx.doi.org/10.5772/intechopen.103160*


The probe stylus of a device is in direct contact with the evaluated surface, **Figure 3**.

The sharp stylus of the profilometer sensor converts the distribution on the surface roughness on mechanical movement, which is then processed by the sensor into an electrical signal and further interpreted as the numerical value of the selected surface roughness parameters of micro-geometry, as well as the graphic record of the surface roughness profile – profilograph.

The some important surface roughness parameters of ISO 4287:1997 are:


In **Table 1**, values of averages of selected surface roughness parameters of blasted surfaces using various blasting materials are listed as steel grit (SG) with

**Figure 3.** *The contact between a profilometer stylus and measured surface.*

**Figure 4.** *Arithmetical mean deviation of the assessed profile Ra.*

**Figure 5.** *Maximum height of the profile Rz.*



#### **Table 1.**

*Arithmetic average of surface roughness parameters of blasted surfaces [5].*

particle size dz. = 0.71 mm, brown corundum (BC) dz. = 0.9 mm, and steel shot (SS) dz. = 0.9 mm. The arithmetic average was calculated from 20 measured.

For all the evaluated surfaces, a comparable surface roughness parameter Ra was achieved; however, values of other surface roughness parameters (Rz – maximum height of profile, RSm – mean width of the profile elements, RPc –peak count per a length unit) are different, and it depends on used type of a blasting material. Individual profiles with material ratio curves of blasted surfaces also show differences between the surfaces, **Figure 7**.

Differences in the micro-geometry of surfaces blasted by BM of different shape (rounded and sharp-edged) are concisely expressed by profilographs and material ratio curves (Abbot Firrestone curves), **Figure 7**. By comparing the material ratio curves of the assessed profile it is possible to explain the difference between surfaces blasted by sharp-edged and rounded blasting material and therefore by the course of material ratio curve in upper level of cut (cca 40%). Bigger material portion in the

#### *Surface Characterization after Blasting DOI: http://dx.doi.org/10.5772/intechopen.103160*

**Figure 7.**

*The profiles of surfaces blasted with different blasting materials [5]. (a) the profilograph of a surface blasted by steel shot, (b) the profilograph of a surface blasted by steel grit, and (c) the profilograph of a surface blasted by brown corundum.*

level is achieved at surfaces which are blasted by sharp-edged devices, what creates more suitable conditions for good anchoring of subsequently applied coatings.

The shape of valleys at surfaces blasted by sharp-edged blasting materials also play a notable role (formation of wedge or anchor profile elements) in anchoring the coatings into more rugged and more heterogeneous reliefs regarding the shape, which are achieved for those surfaces.

In the complex appraisal of the blasted surfaces micro-geometry an evaluation by a set of chosen surface roughness parameters is necessary. According to the analysis, the most suitable surface roughness parameters are:


By the combination of those surface roughness parameters it is possible to expertly distinguish differences in micro-geometry of blasted surfaces, what is important in terms of further technologies, which led to their creation [11, 14].
