The steel grade SAE 4140 has been nitrided and coated with amorphous diamond like carbon (DLC) from type a-C:H:Si. The nitriding and coating with diamond like carbon was carried out in a plasma assisted nitriding furnace which is extended by plasma assisted chemical vapour deposition for a-C:H:Si coating. The nitriding before coating has been done to increase adhesion and reduce the hardness gradient between the diamond like carbon layer (810 – 1125HV) and the sample material (325HV).

The temperature of the coating process has been varied, from 400 to 550°C. These different samples have been analysed to obtain corrosion resistance data using potentiodynamic polarisation and a salt spray test. The chemical composition of the a-C:H:Si coating has been analysed using glow discharge optical emission spectroscopy (GDOES). Hardness of the coating was identified with nanoindentation. Scanning electron microscopy coupled with energy dispersive x-ray spectroscopy was utilized to analyse the structure and defects on samples after corrosion test.

Subject
Coatings, Materials, Diamond, Current densities, Surface layers, Salt spray corrosion testing, Steel, Carbon, Corrosion resistance, Hardness, Nitriding, Corrosion potential, Samples
Keywords:
diamond like carbon, a-C:H:Si, DLC nitriding steel grade, potentiodynamic polarization
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2014
Association for Materials Protection and Performance (AMPP)
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