EFFECT OF THERMOCYCLIC ELECTROLYTE-PLASMA TREATMENT PARAMETERS ON THE STRUCTURAL-PHASE STATE AND TRIBOCORROSION BEHAVIOR OF 12KH1MF STEEL

Abstract

In this work the influence of regimes of thermocyclic electrolyte-plasma treatment (TEPT) on structure-phase state, microhardness and tribocorrosion behavior of 12Kh1MF heat resistant low alloy steel for power plant steam pipelines and boilers is investigated. TEPT was performed in 10 % aqueous solution of Na2CO3. Voltage varied from 300 V (30 А) to 150 V (8 А) every 5 s. Three regimes were considered at maximum surface temperature from 800 to 900 °С. Samples were studied by SEM, X-ray phase analysis, Vickers microhardness test, ball-on-disk tribology test and neutral salt spray corrosion tests. TEPT has a layered structure - thermocyclic hardening zone, heat affected zone and base material. Hardened layer thickness is from 400 to 600 μm according to regimes. Ferrite pearlite initial structure transforms into martensite (α'-Fe) with Fe3C carbides. Consequently, microhardness increases from 205 to 345-373 HV 0.1 (almost 1.7-1.8 times). Friction factor reduces from 0.627 to 0.596-0.617; wear intensity decreases