Mechanical characterization and single asperity scratch behaviour of dry zinc and manganese phosphate coatings

The goal of this study is to characterise the mechanical properties of zinc and manganese phosphate coatings before and after running in. The characterization is done with nano-indentation to determine the individual crystal hardness and single asperity scratch tests to investigate the deformation behaviour at the single asperity level. The nano-indentation and scratch tests reveal brittle deformation behaviour for the as received coatings. Under uni-directional sliding both layers reduce to a powder which is subsequently compacted to a so called glaze layer. The smooth and brittle glaze layer has a higher hardness compared to the as received coating and its properties can be satisfactorily described by models normally used for a hard coating on a soft substrate.