Characterization of Plasma Nitrided and PVD-TiN Duplex Treated Armco Iron and En40B Steel by Nanoindentation

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Abstract
The nanoindentation test has been applied to evaluate the mechanical properties such as hardness, elastic moduli and deformation behaviors of Fe4N iron nitride layers produced on Armco iron and En40B steel by plasma nitriding, and PVD-TiN coatings deposited on En40B with or without prior plasma nitriding treatment. Results showed that the Fe4N layer produced on En40B exhibits higher hardness than that on Armco iron. This is attributed to the effect of the alloy compositions, especially Cr element. However, similar elastic modulus values to that of bulk ferrous alloys have been found for Fe4N layers produced on both Armco iron and En40B. Under lower loads, TiN coatings on nitrided substrate behave quite the same in hardness and elastic modulus as TiN coatings on untreated En40B. Whilst with increasing indentation load and depth, duplex treated (i.e., combined plasma nitriding and PVD-TiN coating) En40B possesses higher composite hardness, elastic modulus and load bearing capacity than TiN coated base material.