**2. Materials, equipment, and scientific methodology**

#### **2.1 Materials**

Six P410D ferritic stainless steel specimens were used—named "*Specimen 1*", "*Specimen 2*", … , "*Specimen 5*" and "*Specimen 6*". The chemical composition of P410D ferritic stainless steel is specified in **Table 1**.

Each specimen had dimensions of, approximately, 27*x*10*x*5 [mm], being conditioned under different parameters of heat treatment of quench, in a combustol oven, whose application temperatures were monitored by thermocouples. **Table 2** shows the temperature values adopted for the heat treatments of the specimens.

After heat treatments of quench, the specimens were subjected to metallographic analysis, being, initially, hot embedded, sanded, polished and chemically etched with CATELA—2 g of picric acid, 6 ml of acetic acid, 3 ml of hydrochloric acid, and 100 ml of ethyl alcohol. After, microstructural images were acquired by optical microscopy.

As counter-body, an AISI 52100 steel bearing (quenched and tempered) was used, with diameter *<sup>D</sup>* = 25.4 mm (*<sup>D</sup>* = 1″—*standard size*).

**Figure 4** presents an image of the AISI 52100 steel bearing microstructure and its chemical composition. Its microstructure is composed only of two phases: the tempered martensitic matrix (with the characteristic shading contrast) and the small M3C carbide precipitates homogeneously distributed. The darker and lighter areas in the matrix are typical of tempered martensite and show the gradients of etching depending on the orientation of the martensite lenses and the density of the carbide precipitation in different regions (due to small differences in chemical composition).

The abrasive slurry was prepared with black silicon carbide (SiC)—average abrasive particle size of *ap* = 3 μm—and distilled water. **Figure 5** shows an image of the SiC


#### **Table 1.**

*Chemical composition of P410D ferritic stainless steel—% mass.*

*Analysis of the Effect of Heat Treatment Conditions of a Ferritic Stainless Steel … DOI: http://dx.doi.org/10.5772/intechopen.101839*


#### **Table 2.**

*Temperature values defined for the heat treatments of P410D ferritic stainless steel specimens.*


#### **Figure 4.**

*Microstructure and chemical composition of the AISI 52100 bearing steel sphere—Metallurgical state: Quenched in oil at 860°C and stress-relieved at 200°C for 1 h.*

abrasive particles (**Figure 5a**), which was obtained by scanning electron microscopy (SEM), and its abrasive particle size distribution (**Figure 5b**).

**Table 3** presents the hardness values of the materials used in this work (specimens, test ball, and black silicon carbide). The numbers of the specimens were established in ascending order, along with the respective hardness values.

### **2.2 Tribometer**

**Figure 6** shows the ball-cratering tribometer used in this work. Having a "*fixedball*" mechanical configuration, the test shaft was divided into two distinct parts,

#### **Figure 5.**

*Abrasive particles of black silicon carbide (SiC): (a) image obtained by scanning electron microscopy (SEM) and (b) particle size distribution.*


#### **Table 3.**

*Hardness of the materials used in this work.*

called "*motor test shaft*" and "*moving test shaft*" (**Figure 6a**). In turn, each of these parts has a face with a concave radius of *R* = 12.7 mm (*R* = ½"), thus, enabling the accommodation of a test sphere of diameter *<sup>D</sup>* = 25.4 mm (*<sup>D</sup>* = 1″). For the application of the normal force—*N*, was adopted a "*dead weight*" mechanical system (**Figure 6b**).

The "*motor test shaft*" is driven by a direct current electric motor of power *P* = 30 W (**Figure 6a**), under a rotating speed of *n* = 56 rpm.

Finally, the fixation of the specimen is performed by device shown in **Figure 7**. **Figure 8** shows one of the specimens before the tribological tests.

#### **2.3 Research methodology**

**Table 4** shows the test conditions established for the micro-abrasive wear experiments. A normal force value was defined for the tribological tests, *N* = 2 N, together with an abrasive slurry concentration of *C* = 25% SiC + 75% distilled water—in volume.

The test time, for all wear experiments, was established at the value of *t* = 20 min. With the test ball diameter of *D* = 25.4 mm and a ball rotating speed of *n* = 56 rpm, a sliding distance of *S* ≈ 90 m was calculated.

*Analysis of the Effect of Heat Treatment Conditions of a Ferritic Stainless Steel … DOI: http://dx.doi.org/10.5772/intechopen.101839*

#### **Figure 6.**

*Tribometer "*ball-cratering*" of "*ball-fixed*" mechanical configuration: (a) "*motor test shaft*", "*test ball*" and "*moving test shaft*" mounted on the tribometer; (b) application of normal force by "*dead-weight*" mechanical system.*

For each specimen, three ball-cratering micro-abrasive wear tests were conducted and, during the experiments, the abrasive slurry was continuously dripped between the specimen and the test ball.

#### **Figure 8.**

*Image of "*Specimen 5*", before the ball-cratering wear tests.*


#### **Table 4.**

*Test conditions defined for the micro-abrasive wear tests by fixed rotating ball.*

All wear craters were generated without removing the specimens from the clamping device available in the equipment since it has the "horizontal" and "vertical" positioning displacements feature.

Diameters of the wear craters (*b*) developed during micro-abrasive wear tests were measured by optical microscopy. Subsequently, the values of the wear volume (*V*) of the respective wear craters were calculated using Eq. (2):

$$V \cong \frac{\pi .b^4}{64.R} \text{ for } b \ll R \tag{2}$$

Where "*R*" is the radius of the test ball.

Finally, the effect of the heat treatment conditions on P410D ferritic stainless steel was validated based on the statistical analysis of the wear craters volumes and on the behavior of the wear volume as a function of the hardness of each specimen—*V* = *f*(*H*), respectively.
