A Study of the Microstructures and Mechanical Properties of Few-Um-Thin Cr-Based Alloy Deposited Medium Carbon Steel Specimens

Under the financial support from MOST, the project applicant has developed several electroplating baths to obtain Cr-based alloy deposits at relatively high electroplating current densities. Based on the results, 15 SCI articles were published and two innovation patents from ROC were obtained. In this project, a 5-μm-thin Cr-based alloy deposits were electroplated on medium carbon steel (S55C) by means of two electroplating methods. The aim of this project is to evaluate the results with the electroplating methods and recognize the properties of Cr-based-alloy deposited specimens. In the first year, the electroplating was conducted on the steel substrate which could be spheroidized, normalized, quenched, or quench-annealed. Two electroplating methods are used in this project, that is, 1-μm-thin Ni undercoating followed by Cr-based alloy electroplating, and anodic etching followed by Cr-based alloy electroplating. The latter use anodic dissolution of the steel substrate and then electroplate Cr-Fe-based alloy deposits. During anodic dissolution, in the near the steel substrate, abundant Fe2+ ions can be found which could reduce together with Cr3+ ions to form Cr-Fe-based alloy deposits. Some electroplated specimens will be annealed at 500oC to harden the Cr-based alloy deposits. To evaluate the performance of two electroplating methods and the properties of electroplated specimens, microstructure study, electrochemical corrosion, hardness, and scratch tests as well as surface morphology examination will be conducted. In the second year, the tensile and fatigue behavior of electroplated specimens is investigated. The results of stress-strain and S-N curves will be estimated to clarify the effect of 5-μm-thin Cr-based alloy deposit on their tensile and fatigue properties. This can be realized through fractographic study and microstructure examination of fracture specimens after tensile and fatigue tests. The experimental results can be published 2 articles in SCI journals and applied 1 innovation patent per year.

Project ID:PB10708-2355
External Project ID:MOST107-2221-E182-004