**4.1 Corrosion resistance of austenite of single-phase (***A***) steel 08Cr18Ni10Ti (№1) at uniaxial compression of specimens to the formation of deformation martensite**

The effect of "growth" of the paramagnetic state, i.e. increase of the specific magnetic susceptibility of austenite <sup>χ</sup><sup>0</sup> (*A*) from 2.81�10�<sup>8</sup> <sup>m</sup><sup>3</sup> /kg to the maximum value of 3.2 � <sup>10</sup>�<sup>8</sup> <sup>m</sup><sup>3</sup> /kg of steel №1 at uniaxial compression *D* from 0 to 4.85%. With a further increase in deformation (accumulation of α<sup>0</sup> -martensite) from *DS* = 4.85% (true martensite point [7]), the specific magnetic susceptibility of austenite did not change and remained equal to χ<sup>0</sup> max = 3.2�10�<sup>8</sup> <sup>m</sup><sup>3</sup> /kg = const. **Table 6** shows the results of experimental studies of steel №1 (at 20°C) [15].

In **Figure 7** (figures indicate the sample numbers from **Table 6**) shows the change in the corrosion rate *K*(*A*) of austenite samples of single-phase (*A*) steel №1, deformed before the formation of α<sup>0</sup> -martensite, from changes in the atomic-magnetic state, which is characterized by specific magnetic susceptibility χ<sup>0</sup> (*A*) austenite.

With uniaxial compression of austenitic specimens, the corrosion rate *K*(*A*) increases with the "increase" of the atomic-magnetic state (χ0(*A*)), i.e., with an


### **Table 6.**

*The value of the amount of ferrophase* P*α*0*, the specific magnetic susceptibility χ0(*A*), the resulting magnetic susceptibility χ*<sup>∞</sup> *of the sample and the corrosion rate* K *after deformation by compression of steel samples №1, 08Cr18Ni10Ti.*

### **Figure 7.**

*Change in the corrosion rate* K*(*A*) of austenite steel samples 08Cr18Ni10Ti (№1), deformed by compression (degree of deformation—number near points) to the emergence of α*<sup>0</sup> *-martensite deformation (γ* ! *γ*<sup>0</sup> *), from changes in the magnetic state of austenite (χ0).*

increase in the specific magnetic susceptibility χ0(*A*) of austenite, the corrosion rate *K*(*A*) increases (corrosion resistance decreases).

### **4.2 Corrosion resistance of two-phase (***A* **+** *M***) steel 08Cr18Ni10Ti (№1) at uniaxial compression (occurrence of α**<sup>0</sup> **-martensite)**

With increasing degree of plastic deformation compression after the actual deformation point *DS* = 4.85% occurs and accumulates α<sup>0</sup> -martensite deformation, i.e. the continuation of the curve (see **Figure 7**) is the curve after *DS*, which is presented in **Figure 8**. Hence we have that the corrosion rate of two-phase (*A* + *M*) steel №1 increases with increasing plastic deformation. As indicated, after deformation *DS* = 4.85% and above, the value of χ<sup>0</sup> max(*A*) = 3.2 � <sup>10</sup>�<sup>8</sup> <sup>m</sup><sup>3</sup> /kg remains constant, i.e. χ<sup>0</sup> max(*A*) = *const*. Therefore, the corrosion of austenite after this point (*DS*) is constant. Therefore, the corrosion rate of steel 08Cr18Ni10Ti (№ 1) in the area *D* = 0...4.85% increases due to the deformation of austenite, and in the area *D* ≥ 4.85% increases due to corrosion of α<sup>0</sup> -martensite deformation that accumulates when a constant value of the corrosion rate of austenite [15].

The dependence of the corrosion rate *К*(*А + М*) on the amount of α<sup>0</sup> -martensite deformation *P*α<sup>0</sup> occurring during steel compression №1 is shown in **Figure 9**. As we can see, the corrosion rate increases with increasing amount of α<sup>0</sup> -martensite *P*α0.

### **4.3 Corrosion resistance of deformation α**<sup>0</sup> **-martensite (***M***), which occurs during uniaxial compression of steel 08Cr18Ni10Ti (№1)**

The maximum value of the specific paramagnetic susceptibility of austenite χ0 max(*A*) = 3.2 � <sup>10</sup>�<sup>8</sup> <sup>m</sup><sup>3</sup> /kg = *const* corresponds to *K*(*A*) ≈ 24%/h (see **Figure 8**). If we subtract this value of the corrosion rate of austenite *K*(*A*) from the final

*Dependence of Corrosion Resistance of Austenitic Chromium-Nickel Steels on the Magnetic… DOI: http://dx.doi.org/10.5772/intechopen.102388*

### **Figure 8.**

*Change in the corrosion rate of steel samples 08Cr18Ni10Ti (№1) during the transition from single-phase state* K*(*A*) to two-phase state* K*(*A *+* M*) (amount of α*<sup>0</sup> *-martensite deformation—number near points).* DS*—real deformation martensitic point (beginning γ* ! *α*<sup>0</sup> *transformation).*

### **Figure 9.**

*Change in the corrosion rate* K*(*A *+* M*) from the content of α*<sup>0</sup> *-martensite deformation under uniaxial compression (degree of deformation—number near the points) of steel samples 08Cr18Ni10Ti (№1).*

corrosion rate *K*(*A* + *M*) (see **Figure 9**), we obtain the value of the corrosion rate *K* (*M*) from the amount of α<sup>0</sup> -martensite (**Figure 10**). Hence, we have that the corrosion rate *K*(M) increases with increasing amount of *P*α<sup>0</sup> α<sup>0</sup> -martensite deformation.

In **Figure 11** presents a model of corrosion processes for single-phase (separately austenite (*A*) and α<sup>0</sup> -martensite deformation (*M*)) and two-phase (*A* + *M*) states of steel 08Cr18Ni10Ti (№1) [15].

*Change of corrosion rate* K*(*M*) from the content of α*<sup>0</sup> *-martensite deformation* P*α*<sup>0</sup> *under uniaxial compression (degree of deformation—number near points) of steel samples 08Cr18Ni10Ti (№1).*

### **Figure 11.**

*Change of corrosion rate* K*(*A *+* M*),* K*(*M*),* K*(*A*) from the degree of deformation* D *by compression of steel samples 08Cr18Ni10Ti (№1).* DS*—real deformation martensitic point (beginning γ* ! *α*<sup>0</sup> *transformation);* P*α*0*—amount of α*<sup>0</sup> *-martensite deformation (numbers near the points of the curve* K*(*M*)).*

### **4.4 Corrosion resistance of three-phase (***А* **+** *F* **+** *М***) steel 08Cr18Ni10Ti (№ 2) after bending of samples at an angle of 180° from the initial atomic-magnetic state (χ0(***F* **+** *М***)) of austenitic matrix containing δ-ferrite and α**<sup>0</sup> **-martensite deformation**

From the industrial sheet steel №2 were cut from different cities on 3 adjacent samples with the subsequent averaging of the measured values (amount of δ-ferrite, α0 -martensite, corrosion rate *K*, specific magnetic susceptibility χ<sup>0</sup> austenite). A total of 18 samples were cut, from which 6 averaged samples were grouped, i.e. 6 "points". The average values of the amount of δ-ferrite and the specific magnetic susceptibility of χ0(*F*) austenite in the presence of δ-ferrite were measured before bending deformation, and the amount of total δ-ferrite and α<sup>0</sup> -martensite after bending deformation (180°).

Six samples were obtained with averaged values of *P*<sup>δ</sup> before deformation and *P*δ+α0(180) after bending at an angle of 180°. For each of the three neighboring samples according to the method determined χ∞(*F*) and from the graphical dependence χ∞(*F*) *= f*(*P*δ) by extrapolation (*P*<sup>δ</sup> ! 0) found the specific paramagnetic susceptibility of the austenitic matrix χ0(*F*), which contains δ-ferrite. The results obtained are given in **Table 7**. According to the literature, the amount of δ-ferrite *P*<sup>δ</sup> during deformation does not change and subtracting it from the experimentally found values of *P*<sup>δ</sup> <sup>+</sup> <sup>α</sup>0(180), found the amount of formed α<sup>0</sup> -martensite deformation *P*α0(180) (**Table 7**).

From the graphical dependence of χ∞(*F* + *М*) on *P*<sup>δ</sup> <sup>+</sup> <sup>α</sup><sup>0</sup> (by analogy with steel №1) by the method of extrapolation, when *P*<sup>δ</sup> <sup>+</sup> <sup>α</sup><sup>0</sup> ! 0 (both ferrophases are absent) found the value of the specific magnetic susceptibility of austenite χ0 max(*A*) = 2.2 � <sup>10</sup>�<sup>8</sup> <sup>m</sup><sup>3</sup> /kg = *const* (for austenitic matrix of steel №2, which contained δ-ferrite (*F*) and α<sup>0</sup> -martensite (*M*)).

In **Figure 12** [15] presents the change in the corrosion rate *K*(*A* + *F* + *M*) of three-phase (*A* + *F* + *M*) steel №2 after bending the samples at an angle of 180° from the magnetic state (χ0(*F* + *M*)) of the austenitic matrix, which contains δ-ferrite and α<sup>0</sup> -martensite.

From **Figure 12** we have that the corrosion rate of three-phase (*A* + *F* + *M*) steel №2 after bending of two-phase (*A* + *F*) samples by an angle of 180° increases with increasing specific magnetic susceptibility χ0(*F* + *M*) of the original samples with δ-ferrite. Thus, the content of phases (*A* + *F* + *M*) increases the corrosion rate. A similar dependence of *K*(*A* + *F* + *M*) on *P*<sup>δ</sup> <sup>+</sup> <sup>α</sup><sup>0</sup> is shown in **Figure 13**.


### **Table 7.**

*The value of the amount of ferrophase, the specific magnetic susceptibility χ0(*F*) of the original samples and the corrosion rate* K*(*A *+* F *+* M*) after deformation by bending at an angle of 180° steel samples №2.*

### **Figure 12.**

*Relationship between the corrosion rate* K*(*A *+* F *+* M*) of three-phase (*A *+* F *+* M*) steel 08Cr18Ni10Ti (№2) after bending two-phase (*A *+* F*) samples at an angle of 180° and the atomic-magnetic state (χ0(*F + М*)) austenitic matrix of samples containing δ-ferrite (*F*) and α*<sup>0</sup> *-martensite deformation (*M*).*

### **Figure 13.**

*Relationship between the corrosion rate* K*(*A *+* F *+* M*) of three-phase (*A *+* F *+* M*) steel 08Cr18Ni10Ti (№2) after bending the two-phase (*A *+* F*) samples at an angle of 180° and the total number of* P*<sup>δ</sup> <sup>+</sup> <sup>α</sup>*<sup>0</sup> *samples containing δ-ferrite (*F*) and α*<sup>0</sup> *-martensite deformation (*M*).*

*Dependence of Corrosion Resistance of Austenitic Chromium-Nickel Steels on the Magnetic… DOI: http://dx.doi.org/10.5772/intechopen.102388*

**Figure 14.**

*Change in the corrosion rate* K*(*A *+* F*) from the specific magnetic susceptibility χ0(*F*) (a) of the austenitic matrix of samples (containing δ-ferrite) and the content of* P*<sup>δ</sup> δ-ferrite (b) steel 08Cr18Ni10Ti (№2).*
