**1. Introduction**

Stainless steel is an iron-chromium-carbon alloy that has high resistance to oxidation and corrosion in varying environments. In addition to the presence of nickel (Ni), the main alloying element that ensures the chemical resistance to oxidation and corrosion is chromium (Cr), with 11% concentration by mass; such resistances are associated with the formation of a mixed oxides layer and its dissolution in the medium in which it is exposed. Based on the predominant constituent phase in its microstructure, stainless steels are classified mainly into three categories: *austenitic*, *ferritic*, and *martensitic* [1]. Thus, in Fe-Cr phase diagram (**Figure 1** [2]), the "*ferritic stainless steels*" are at the right of the austenitic field [3] and are classified as "*ferritic*

**Figure 1.** *Fe-Cr phase diagram [2].*

*stainless steels*" the materials with a percentage greater than 12% Cr—by mass [3], possessing body-centered cubic crystalline structure.

In the ferritic microstructure, chromium (Cr) is configured as a substitutional atom, influencing hardening by solid solution [4], where "*hardness*" is a direct indicator of the wear resistance of ferritic stainless steels influenced by the type of heat treatment conducted. Additionally, some ferritic stainless steels can be austenitized at high temperature and cooled in a quench process, to obtain martensitic microstructure, which presents a high density of discordances.

In another scientific segment, the "*X-ray diffraction*" technique is applied for measuring residual stresses in metallic materials. It is conceptualized in the deviation of the propagation trajectory suffered by X-ray waves and is compared with the positions of the atoms of the analyzed material due to the changes caused by residual stresses themselves of the network parameters in the material [5] (**Figure 2**).

In X-ray diffractometer, there is a coordinated movement between the Coolidge tube—generator of the X-rays—and the specimen. The rotational motion of the Coolidge tube defines the "*angle of incidence of the X-rays—θ*" on the surface of the material and the rotational movement performed by material analyzed defines the "*angle of rotation of the specimen—ψ*" (**Figure 3**).

As the specimen is rotated by a defined angle *ψ*, the angle of incidence of the X-rays (*θ*) is altered accordingly. The angle of rotation of the specimen (*ψ*) is measured in relation to a normal axis to the atomic planes, defined by "*Miller indexes hkl*", parallel to the surface of the specimen and the angle of incidence of the X-rays (*θ*) is referenced in relation to the surface of the material.

From there, a graph of *θ* = *f*(sen<sup>2</sup> *ψ*) is raised, which results in a 1st Degree Equation (Eq. (1)), by which the residual stress is calculated. This technique is called "*sen*<sup>2</sup> *ψ*".

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

**Figure 2.**

*Physical principle of the "*X-ray diffraction*" technique.*

#### **Figure 3.**

*"*X-ray diffraction*": Definition of the angles "θ" and "ψ"—"*angle of incidence of the X-rays*" and "*angle of rotation of the specimen*", respectively.*

$$
\sigma\_{\rm ret} = m \frac{E}{2(1+\nu)} \cot \left(\theta\_0 \right) \tag{1}
$$

In Eq. (1), "*m*" is the angular coefficient of the generated straight line, "*E*" and "*ν*" are the longitudinal elasticity modulus and the Poisson coefficient of the analyzed material, respectively, and "*θ*0" is obtained for *ψ* = 0°. For *m* < 0, the residual stress acting on the material will be "*compressive*" and, for *m* > 0, the residual stress will be "*tractive*".

On the tribological side, "*wear*" can be defined as "*damage on the solid surface, involving progressive loss of mass, due to the relative movement between the surfaces and contact with other material or materials*" [6]. Together with the given general definition, each type of wear has a specific setting—"*Abrasive wear*", as discussed in this work, is due to hard particles, or hard protuberances, forced against and moving along a solid surface [7].

In industrial sectors where wear causes downtime, there occur decrease in production and involve high maintenance costs, so it is not enough to acquire knowledge only in mechanical and/or metallurgical manufacturing of materials and processes—it is also important to research and to understand the wear processes that act in specific working conditions.

Through analyses of wear craters generated during micro-abrasive wear tests by rotating ball, it is possible to predict or, at least, estimate the abrasive wear behavior of a material or any mechanical component in real working conditions. Additionally, such analyses can be expanded and better understood along with residual stress measurements conducted by the "*X-ray diffraction*" technique.

Thus, the objective of this work was to analyze the effect of heat treatment on residual stresses and tribological behavior of a dual-phase stainless steel, under conditions of micro-abrasive wear.
