**4. Magnetometric evaluation of corrosion resistance of austenitic chromium-nickel steels depending on the phase composition (***A, F, M***) after deformation by compression and bending of specimens**

Despite numerous studies of corrosion processes in stainless austenitic steels, which are widely used in aviation and nuclear energy, questions concerning the nature of corrosion still remain unclear. Many works are devoted to the influence of α-phase (δ-ferrite, α<sup>0</sup> -martensite deformation) on the corrosion resistance of steels [4, 5, 13, 14]. However, the corrosion resistance of austenite (*A*), δ-ferrite (*F*) and α0 -martensite deformation (*M*) and the phases *A* + *F*, *A* + *M*, *A* + *F* + *M* present together are insufficiently studied. In [13] it was found that the significant cause of corrosion resistance of austenitic steels is not the low content of the α-phase, but the atomic-magnetic state of the austenitic matrix, which is determined by the specific magnetic susceptibility.

To clarify the role of paramagnetic austenite (*A*), δ-ferrite (*F*), α<sup>0</sup> -martensite deformation (*M*) in the individual and total influence of the phases *A* + *M*, *A* + *F*, *A* + *F* + *M* on the corrosion resistance of chromium-nickel steels austenitic class were selected two industrial stainless steels (№1 and №2) of one grade 08Cr18Ni10Ti (sheets with a thickness of 1 mm) with a slight difference in the content of Ni and other elements.

Chemical composition of steels (% wt.): №1—0.08 C; 17.74 Cr; 10.56 Ni; 0.259 Ti; 0.982 Mn; 0.23 Si; 0.04 S and №2—0.09 C; 18.2 Cr; 10.1 Ni; 0.56 Ti; 0.75 Mn; 0.7 Si; 0.01 S; 0.026 P; 0.14 Cu; 0.05 Co; 0.04 V; 0.04 W; 0.06 Mo.

The samples were cut by cold mechanical method in the form of rectangular parallelepipeds of approximately the same size 7 � <sup>3</sup> � 1 mm3 . The degree of residual deformation *D* was calculated by the ratio of thickness before (*d*0) and after (*d*) deformation (*D* = (*d*0–*d*)/*d*0). After compression deformation, the samples were tested for corrosion. In order to accelerate chemical corrosion, the test samples were placed in a mixture of concentrated acids-hydrochloric and nitric (HCl:HNO3 3:1) and kept for 1 h. To visually detect changes in the corrosion rate, we used the coefficient of intense corrosion *K*, which was defined as the relative mass loss *К* = (Δm/(m � τ)) � 100%.

Austenitization of steel №1 was performed in the standard way (annealing at 1050°C, holding for 30 min, followed by quenching in water). After such heat treatment, the steel №1 in the initial state was paramagnetic, ie single-phase (*A*) with a specific magnetic susceptibility of austenite <sup>χ</sup><sup>0</sup> = 2.81�10�<sup>8</sup> <sup>m</sup><sup>3</sup> /kg.

Samples of №2 steel containing δ-ferrite in the initial state were not subjected to austenitization, i.e. in the initial state it was two-phase (*A* + *F*), which were tested after bending at an angle of 180°. After testing the samples with a length of 7 mm per bend, the amount of deformation martensite was distributed unevenly from the *Dependence of Corrosion Resistance of Austenitic Chromium-Nickel Steels on the Magnetic… DOI: http://dx.doi.org/10.5772/intechopen.102388*

ends to the ribs. Therefore, the average value of the amount of α<sup>0</sup> -martensite for the whole sample was approximated. Due to the fact that the low content of δ-ferrite is unevenly distributed over the width of the cold-rolled sheet in steel №2 [5] and in order to further average the results from different places were cut three, adjacent samples, which after averaging were assigned numbers 1...6.

Steel №1 was tested under uniaxial compression, and steel №2—under deformation by bending.
