Indentation behavior and Young's modulus evaluation in electroless Ni modified CrN coating on mild steel

The acid hypophosphite-reduced bath is applied to deposit electroless Ni-P( EN) on the mild steel (MS) substrate and the CrN film is coated on the Ni-P modified substrate by reactive r.f. sputtering. A coating configuration of Ni/Ni3P/MS is fabricated as the precipitation Ni3P phase is formed due to the elevated substrate annealing during r.f. sputtering. Microhardness, You ng's modulus and indentation behavior of the EN/MS and CrN/Ni-Ni3P/MS are i nvestigated. The measured microhardness of the complex coating assembly is increased due to the employment of electroless Ni as the interlayer in the CrN/MS system. The indentation and cracking tester (ICT) is further employe d to investigate the indentation behavior of the coating assembly. The load ing-unloading curves of as-plated and heat-treated electroless Ni-P layers with different thickness are evaluated. In addition, the Young's modulus of the coating can be derived with appropriate load applied. (C) 2001 Elsevie r Science B.V. All rights reserved.