Optimizing Heat Treatment for Electroplated NiP and NiP/SiC Coatings

Donya Ahmadkhaniha,Fredrik Eriksson,Caterina Zanella

doi:10.3390/coatings10121179

Donya Ahmadkhaniha, Fredrik Eriksson + Show 1 more

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https://doi.org/10.3390/coatings10121179

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Journal: Coatings	Publication Date: Dec 1, 2020
Citations: 13	License type: CC BY 4.0

Affiliation: Jönköping University, Linköping University

Abstract

NiP (P > 10 wt.%) coatings are amorphous coatings whose structure can be transformed by heat treatment into a crystalline structure and hardened by precipitation of Ni3P. In this study, NiP coatings and composite ones with SiC nanoparticles were produced by electrodeposition, and their structural transformation by heat treatment was studied using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The microhardness and the scratch and corrosion resistance of the coatings were evaluated and compared before and after different heat treatments. The results showed that in as-plated condition, the addition of SiC particles in the coatings did not modify the microstructure, microhardness, or electrochemical behavior. However, the SiC particles’ role was disclosed in combination with heat treatment. Composite coatings that were heat treated at 300 °C had higher microhardness and scratch resistance than the pure NiP one. In addition, composite coatings maintained their scratch resistance up to 400 °C, while in the case of the NiP ones, there was a reduction in scratch resistance by heating at 400 °C. It was also concluded that heating temperature has the main role in hardness and corrosion resistance of NiP and composite coatings, rather than heating time. The optimum heat-treatment protocol was found to be heating at 360 °C for 2 h, which resulted in a maximum microhardness of about 1500 HV0.02 for NiP and its composite coating without sacrificing the corrosion resistance.

Highlights

NiP coatings have mainly been produced by electroless deposition, which can deposit a uniform coating on samples with recesses and complex geometry [1,2,3]
The following pre-treatments were applied on the steel substrates: mechanically grinding with SiC papers, ultrasonically cleaning in an alkaline soap, rinsing with distilled water, immersing 8 min in 2.5 M H2 SO4 at 50 ◦ C, and rinsing with distilled water; the samples were immersed in the bath
The current density of 4 A/dm2 and a bath temperature of 70 ◦ C were chosen for the deposition

Summary

Introduction

NiP coatings have mainly been produced by electroless deposition, which can deposit a uniform coating on samples with recesses and complex geometry [1,2,3]. There are some challenges in controlling electroless nickel-plating solutions. Electroless solutions have a complex composition, including complexing agents, buffering agents, stabilizers, and reducing agents, which makes their production, maintenance, and disposal sophisticated and expensive. Electroless plating needs a high operating temperature, though it has a low deposition rate. Due to these challenges of electroless plating, electroplating, which was developed by Brenner et al [4] for the deposition of alloy coatings, has gained attention as an alternative deposition process. Electrodeposition can deposit a thick layer of alloy in a relatively short time by means of a simple process [5]

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