Characterization of Fe-W alloys electrodeposited from environmentally friendly electrolyte
Doctoral thesis, 2020

This work focuses on Fe-W and Fe-W/Al2O3 coatings electrodeposited from an environmentally friendly electrolyte: minimally invasive, thermodynamically stable, and without toxic compounds. Such coatings aim to be applied for protective applications and as a sustainable alternative to hard chromium coatings. Therefore, the goal of this thesis is to evaluate the interdependencies between the material characteristics (e.g. composition and structure) and the properties of interest: the mechanical properties as well as wear and corrosion resistance. The structure of the coatings was investigated with various analytical techniques (e.g. XRD, SEM, EBSD, and TEM among others), both in the as-deposited state and after heat treatments. Heat treatments led to microstructural transformations in the Fe-W coatings. Nanohardness and wear measurements were performed to study the influence of such microstructural changes on the mechanical properties and wear resistance of the Fe-W coatings.
The results included in this thesis show that increasing the amount of co-deposited W in the coatings results in a transition from a nanocrystalline to a homogeneous amorphous structure, and to an increase in the thermal stability. In-situ TEM analyses on W-rich coatings (i.e. Fe24at.%W) revealed the formation of crystallites at 400 ℃ within the amorphous matrix. Moreover, a large fraction of the amorphous structure is still preserved upon annealing at 600 ℃, where alpha-Fe nanocrystals are found. The microstructural transformations result in an enhancement of mechanical properties of Fe-W coatings. The Fe-24at.%W coating is characterized with the highest hardness both in the as-deposited and annealed state, where a maximum value of 16.5 GPa is observed after annealing at 600 ℃. However, Fe-W coatings are characterized with rather low wear resistance due to severe tribo-oxidation resulting in high coefficient of friction (COF) and wear rates. A considerable improvement in the wear resistance is obtained with the co-deposition of 12vol.% of Al2O3 particles leading to a reduction in the COF and wear rate. The influence of the co-deposited alumina particles on the corrosion resistance is rather limited, i.e. similar values of the corrosion current are measured for the both the Fe-W/Al2O3 composites and Fe-W coatings. Annealing at 600 ℃ of Fe-W/12%Al2O3 composite leads to a combination of high hardness and high wear resistance which result superior to the hardness and wear resistance of hard chromium coatings.

Virtual Development Laboratory (VDL), Chalmers Tvärgata 4C, Gothenburg
Opponent: Professor Peter Leisner, Jönköping University, Sweden

Author

Antonio Mulone

Chalmers, Industrial and Materials Science, Materials and manufacture

A. Mulone, J. Hildenbrand, U. Klement-Electrodeposition: three steps toward sustainability

A. Mulone, I. Ennenb, A. Hüttenb, U. Klement-In-situ TEM annealing of amorphous Fe-24at.%W coatings and the effect of crystallization on hardness

Nowadays, we are constantly reminded of the importance of adopting a more sustainable lifestyle. We are paying more attention on what we buy, what we eat and how we travel. We are changing our habits with the goal to lower our environmental impact and to preserve our planet. These changes are also occurring in the industrial sector where sustainable approaches are introduced in several manufacturing processes. In fact, being able to combine technological progress with environmental and sustainability measures is one of the most important challenges of our modern society. To help reaching this goal, in 2015 the United Nation proposed 17 goals for a sustainable development which represent a constant reminder of what to achieve for a better and more sustainable future. Each goal is extremely important and calls for immediate actions. Among the UN goals, the goal of a Responsible consumption and production (UN Goal number 12) represents the main guideline for industrial manufacturing processes, such as electrodeposition. Electrodeposition is a process used to deposit a layer of a desired metal from a water-based solution (electrolyte) through the application of current. Today, electrodeposition is a well-established technique used to produce coatings ranging from decorative (e.g. gold or silver for jewelry) to technological applications (e.g. chromium and nickel for anti-wear and corrosion protection). Yet, many electrodeposition processes involve the use electrolytes containing highly toxic chemicals and scarce and non-renewable resources. The European Union has recently addressed this problem with the application of environmental regulations and restrictions for the use of toxic compounds, like in the case of hexavalent chromium (i.e. Cr+6), which is classified as strongly cancerogenic. Therefore, it is important to study and develop coatings which are produced in a sustainable way. Such new coatings would be beneficial both for the environment and the electrodeposition industrial market, whose growth is limited by environmental regulations.
This thesis studies iron-based coatings which are electrodeposited using a sustainable electrolyte: minimally aggressive, thermodynamically stable, and without toxic compounds. The aim of this work is to understand how the composition of the iron-based coatings influences the microstructure and the properties of interest: mechanical, wear and corrosion properties. Heat treatments are performed to optimize both the mechanical performance and the wear resistance of the iron-based coatings, which are compared to the properties of chrome coatings. The promising results presented in this thesis represent an important step toward the application of competitive and sustainable alternatives for coatings produced by environmentally hazardous processes.

Smart ELECTrodeposited Alloys for environmentally sustainable applications: from advanced protective coatings to micro/nano-robotic platforms (SELECTA)

European Commission (Horizon 2020), 2015-01-01 -- 2018-12-31.

Subject Categories

Tribology

Manufacturing, Surface and Joining Technology

Corrosion Engineering

ISBN

978-91-7905-256-0

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4723

Publisher

Chalmers University of Technology

Virtual Development Laboratory (VDL), Chalmers Tvärgata 4C, Gothenburg

Online

Opponent: Professor Peter Leisner, Jönköping University, Sweden

More information

Latest update

3/20/2020