Formation of Surface Ultrafine Grain Structure and Their Physical and Mechanical Characteristics Using Vibration‐Centrifugal Hardening

Abstract

The vibration-centrifugal hardening forms a gradient ultrafine grain structure of the ferritic class with a grain size of 190 nm and a surface microhardness of 8.9 GPa and a depth of up to 6 mm on the surface of 40 Kh steel of the ferritic-pearlitic structure. These parameters are formed due to an increase in the mass of the tool that acts on the processed surface through the balls and depend on the treatment modes. This surface ultrafine grain structure increases the wear resistance properties of steel in oil and oil-abrasive environment and improves the electrochemical characteristics.

Residual Stresses Formed by Vibration‐Centrifugal Hardening

“…To relieve residual stresses after turning, the samples were annealed, heating them to a temperature of 820°C and cooling with a furnace for 8 hours. Work hardening was carried out on a special vibration-centrifugal strengthening device [6] with a special massive tool with balls of 13 mm in diameter fixed on it.…”

“…e material of the component is hardened as a result of the SPD. e design of the tool and its weight make it possible to obtain high contact loads with constant sizes of balls and also provide a fixed direction of movement of the balls fixed in a cage in the radial direction to the workpiece, which increases the depth of work hardening [6]. Balls made of ShKh15 steel have a hardness of HRC 60-62. e samples were fixed on a mandrel.…”

“…In particular, when the NCS and UFGS are formed on the surface, its chemical composition can be changed [1] and it protects the matrix material from hydrogen saturation [2], corrosion [3], wear [4], and contact fatigue [5]. One of the methods for the UFGS formation is vibration-centrifugal hardening (VCH) [6][7][8]. It is shown [6][7][8] that VCH due to the significant weight of the strengthening tool forms a UFGS of high microhardness and considerable (up to 7 mm) depth.…”

“…One of the methods for the UFGS formation is vibration-centrifugal hardening (VCH) [6][7][8]. It is shown [6][7][8] that VCH due to the significant weight of the strengthening tool forms a UFGS of high microhardness and considerable (up to 7 mm) depth.…”

“…In the developed VCH method, the processing regimes can be used to control the parameters of the hardened layer, in particular, the tool weight over a wide range (from 3.5 to 7.5 kg) with a constant diameter of the balls. Such conditions change the depth and microhardness of the surface layer due to changes in contact loads in the treatment zone [6,7].…”