DLC deposited onto nitrided grey and nodular cast iron substrates: An unexpected tribological behaviour

In the pursuit of suitable alternative substrate materials for DLC coatings, grey cast iron (GCI) and nodular cast iron (NCI) stand out due their vast industrial applications, consequence of its sufficient mechanical strength associated with low cost. However, graphite flakes and nodules introduce critical discontinuities on these metallic surfaces. In the present work, the effect of graphite morphology on the tribological behaviour of DLC (a-C:H) obtained via PECVD is analyzed. Scuffing resistance was accessed using dry reciprocating sliding tests, where GCI presented a friction coefficient of 0.06 during a lubricious regime whereas NCI presented μ=0.14. Thus, active friction reduction mechanisms were investigated using additional interrupted tests. The wear tracks were analyzed revealing how tribolayers morphology and chemical nature modified friction. •Investigation of a-C:H coatings using grey and nodular cast iron substrates.•Coated grey cast iron presented a rough topography vs coated nodular cast iron.•COF = 0.06 was found for coated grey cast iron vs Si3N4.•COF = 0.15 was found for coated nodular cast iron vs Si3N4.•Graphitic tribolayers modified wear tracks topography and chemical nature.