The corrosion resistance of 140MXC, 530AS and 560AS coatings produced by thermal spraying

Abstract

Three commercial materials were deposited using electric arc thermal spraying: 140MXC (with Fe, W, Cr, Nb), 530AS (AISI 1015 steel) and 560AS (AISI 420 steel) on AISI 4340 steel. The aim of this paper was to evaluate the best strategy for improving a coating-substrate system’s corrosion resistance, using the following combinations: homogeneous single coatings, bilayers consisting of 530AS or 560AS under 140MXC and 140MXC + 530AS and 140MXC + 560AS coatings deposited simultaneously. The coatings were characterised using optical microscopy, scanning electron microscopy and X-ray diffraction. Corrosion resistance was evaluated through potentiodynamic polarisation and hardness by using the Vickers test. Corrosion resistance depends on the amount of microstructure defects, the deposition strategy and the alloy elements. However, corrosion resistance was similar in single coatings of 140MXC and bilayers, having -630 V corrosion potential and 708 nA corrosion current. The details and corrosion mechanism of the coatings so produced are described in this paper.

Keywords

• Thermal spray
• corrosion
• nanocomposite
• multilayer
• pseudoalloy.