Morphological Changes in the Dislocation Structure of Structural Steel 20GL after Electrolytic-Plasma Hardening of the Surface

Abstract

The work is devoted to the study of the features of the formation of modified surface layers in the electrolytic-plasma coating of the surface of 20GL steel used for the manufacture of parts of a railroad train. The results of the investigation of the effect of the electrolytic-plasma coating on the morphology and the structural-phase state of the surface, the dislocation structure of 20GL steel before and after treatment are presented. It has been established that in the initial state 20GL steel has a ferrite-pearlite structure, and after the electrolytic-plasma coating of the surface, a lamellar structure of perlite and ferrite is observed. It is found that in the initial state 20GL steel has the following average parameters of the fine structure: 〈ρ〉 = 2.41 × 10¹⁰ cm^–2, 〈ρ_±〉 = 2.23 × 10¹⁰ cm^–2, 〈χ〉 = 〈χ_lp〉 + 〈χ_elas〉 = 560 + 25 = 585 MPa, 〈σ_l〉 = 310 MPa, 〈${{\sigma }_{{\text{d}}}}$〉 = 〈$\sigma _{{\text{d}}}^{{{\text{pl}}}}$〉 + 〈$\sigma _{{\text{d}}}^{{{\text{elas}}}}$〉 = 300 + 35 = 335 MPa; and after processing, the average parameters of the fine structure changed as follows: 〈ρ〉 = 1.03 × 10¹⁰ cm^–2, 〈ρ_±〉 = 0.82 × 10¹⁰ cm^–2, 〈χ〉 = 〈χ_pl〉 = 205 MPa, 〈σ_l〉 = 200 MPa, 〈${{\sigma }_{{\text{d}}}}$〉 = 〈$\sigma _{{\text{d}}}^{{{\text{pl}}}}$〉 = 175 MPa.