Summary of fabrication methods of ceramic coated metallic materials.
Surface coating can allow the bulk materials to remain unchanged, while the surface functionality is engineered to afford a more wanted characteristic. Ceramic coatings are considered as ideal coatings on metal which can significantly improve the surface properties of metal materials including anti-fouling, self-cleaning, corrosion resistance, wear resistance, oil/water separation and biocompatibility. Furthermore, various techniques have been utilized to fabricate a range of different ceramic coatings with more desirable properties on metal materials, which make the materials widely used in service environment. This chapter focus will be on the types, fabrication methods, surface properties and applications of ceramics coated metal materials.
- ceramic coating
- metallic materials
- surface physicochemistry
Metallic materials such as Fe, Cu, Ti, Al, Mg and their alloys have excellent mechanical and physical properties showing tremendous application in architecture, marine, aerospace and biomedicine fields, etc. [1, 2, 3, 4, 5, 6]. To a certain extents, the surface properties of the metallic materials are playing irreplaceable roles in operating environments. Surface functionalization can improve corrosion resistance, anti-fouling, self-cleaning, wear resistance, oil/water separation and biocompatibility of metallic materials [7, 8, 9]. In this context, surface coating is an efficient and resource saving method to realize the surface functionalization of metallic materials. In addition, ceramic coating is environmentally friendly, and has the advantages of low cost, simple preparation, corrosion and wear resistance, thermal stability, and mechanical durability . As such, constructing a ceramic coating on metallic material surface is a rational strategy to realize the surface multi-function [11, 12].
In this chapter, we briefly introduce the types and the properties of ceramic coatings. Then, we summarize the strategies for preparing ceramic coatings on metallic materials and applications of ceramics coated metallic materials.
2. Ceramics coated metallic materials
Ceramics materials can be divided into oxide ceramics and non-oxide ceramics according to their compositions. Many oxide ceramics are metal oxides forming oxide films on their surfaces, which are used as coating materials for the protection and functional layer of metallic materials (for example, aluminum, stainless steel or titanium alloys). Also, diverse non-oxide ceramic materials are used to functionalize the surfaces of metal materials.
2.1 Ceramic coatings types
Ti and its alloy have excellent corrosion resistant to alkali, chloride and some strong acids because of the compact oxide film (Titania, TiO2) formed spontaneously on surfaces. Therefore, TiO2 coating is considered to be an ideal corrosion resistant layer to protect the metal substrate from corrosion. Shen
Alumina (Al2O3) exhibits exceptional mechanical property and thermostability possessing a broad range of applications in optics, electronic, and biomedical fields. In addition, the corrosion resistance of Al and its alloys is attributed to inherent Al2O3 coating, which can effectively improve the corrosion resistance of metallic substrate. Gao
Similarly, silica (SiO2) is also highly desirable coating materials on metallic materials as wear and corrosion resistant coating. The corrosion-resistant SiO2 ceramic coating on alloys was prepared by metal organic chemical vapor deposition (MOCVD) . In addition, Sadreddini
As the most stable oxide of manganese, manganese dioxide (MnO2) has abundant reserves in the earth, and has the advantages of low cost, environmental friendliness and simple preparation, which is widely used in energy, catalysis and sewage treatment. MnO2 coating with different crystal structure and surface morphology can be prepared by different methods meeting wanted requirements [20, 21]. Inspired by lotus flower, we used an in situ immersion method to fabricate MnO2 coating on AZ31B Mg alloy, and post-modification with stearic acid to obtain the superhydrophobic MnO2 coating. The prepared superhydrophobic Mg alloy surface showed excellent self-cleaning property both in air and under oil (shown in Figure 1), as well as mechanical durability and chemical stability .
As to non-oxide ceramics, Hydroxyapatite (HA) is the main inorganic component of human and animal bones. It is a kind of bioactive ceramic material, which is widely used in bone tissue engineering. The HA ceramic coating was widely used in surface functionalization of metallic biomaterials. Hiromoto
Additionally, non-oxide ceramics materials such as silicon carbide (SiC), monolithic silicon nitride (Si3N4), and aluminum nitride (AlN) exhibit superior high-temperature strength and durability indicating their potential in industrial application [26, 27]. Furthermore, Liu
In this context, oxide ceramic coatings and non-oxide ceramic coatings are playing important roles in the field of surface functionalization of metallic materials.
2.2 Properties of ceramic coating
Different metallic materials, in a sense, have different mechanical properties. Hardness and wear resistance are required to expand application prospect when metallic materials are used for industrial engineering. Numerous studies have shown that rare earth silicate barrier coatings can be potentially used for the application in high temperature aero-engines . Bio-inspired by lotus leaf, Wu
Metal corrosion is commonly found, hard to prevent, does harm to our environment, and costs several percent of the gross domestic production (GDP) of an industrialized country. As such, establishing corrosion control systems for metallic materials is very important for the sake of environment and economy harmony. The ceramic coating is widely used to protect metallic materials because of its good corrosion resistance. Like other corrosion-resistant coatings, the ceramic coating provides a barrier on the surface of metallic materials effectively isolating the corrosion solution from the substrate . Moreover, the ceramic coating with micro-nano hierarchical structure can be prepared to obtain a superhydrophobic surface after hydrophobic treatment. In this regard, superhydrophobic ceramic coating has favorable corrosion resistance due to its excellent water-repellent property showing great potential application in corrosion protection of metallic materials .
To improve the corrosion resistance of mild steel, Tiwari
Owing to their good thermal barrier properties, ceramic coatings are widely used to provide thermal barrier for heat transfer on the surface of metallic material and to improve the thermal stability of the substrate. Ghosh
Ceramic materials can be divided into bioinert materials and bioactive materials according to their biological properties. Bioinert materials do not induce any visible tissue reactions; the majority of ceramics belong to this group. Al2O3 and ZrO2 as bioinert materials have inherently low levels of reactivity, which have great potential for medical application owing to nontoxic, non-allergenic, and non-carcinogenic .
Some ceramics regarded as bioactive materials favor organ/tissue repairs and the integration of associated devices, which are essentially used in orthopedics, like favor bone repair and the integration of implants in bone tissues. As the most representative bioactive ceramic material, HA is widely used in bone tissue engineering for it is the main component of bones and teeth of human and animal. To improve the biodegradation performance of AZ91D Mg alloy, Song
2.3 Fabrication of ceramic coating on metallic materials
The preparation and application of ceramic coatings have been studied for a long time. In order to adapt to different substrates, various technologies have been developed. These technologies of ceramics coated metallic materials enable to expand the application range in many fields.
Sol-gel method can easily prepare the ceramic coatings on metallic materials. Villatte
Micro-arc oxidation (MAO) has been used as a critical method for many years to prepare much thicker and harder ceramic coatings on metallic materials. Shen
Atomic layer deposition (ALD) is a surface modification method through depositing inorganic species on the surface of different substrates, and the materials with arbitrary shape could be modified through vapor phase ALD. After multiple cycles of deposition, a conformal and uniform ceramic coating with good heat resistance and stiffness would be formed . Huang
Electrochemical method is usually used to fabricate oxide ceramics coated metallic materials. Notably, the electrochemical method is independent on the shape and the size of substrate. As such, Song
As a surface-deposited technology, plasma treatment is a simple and effective way to obtain ceramics coated metallic materials showing fine adhesion strength of coating-substrate. To improve corrosion resistance and bioactivity, the HA coating was prepared on AZ91HP Mg alloy by using plasma spraying method . In addition, Sun
Magnetron sputtering is also an efficient method to prepare ceramic coatings on the surface of metallic materials. Krishna
Solution immersion is a conventional method for fabrication of ceramic coatings on the surface of metallic materials. In this context, it is inexpensive and easy to carry out [52, 53]. In order to obtain a HA coating on Mg and its alloy, Hiromoto
Laser-cladding is considered to be one of the most effective methods to fabricate a ceramic coating on metallic materials because of the powerful energy of laser to accelerate metal oxidation . Boinovich
Chemical vapor deposition can produce the ceramic coatings with controlled surface topography. Hofman
Dip-coating is a time-saving and low-cost method for preparation of ceramic coatings [58, 59]. In 2017, Yu
The fabrication methods of ceramic coated metallic materials are summarized in Table 1.
|Sol-gel||TiO2||Stainless steel||Antibacterial and sufficient|
|SiO2||Titanium alloy||Oxidation resistance|||
|Al2O3||Mild steel||Corrosion resistance|||
|Micro-arc oxidation||TiO2/Al2O3||Ti-6Al-4 V alloy||Wear resistance|||
|Atomic layer deposition||TiO2||Co-Cr||Antifungal|||
|Electrochemical||HA||Mg alloy||Biodegradation performance|||
|Plasma treatment||HA||Mg alloy||Corrosion resistance and bioactivity|||
|Magnetron sputtering||HA||Titanium||Corrosion resistance|||
|TiO2||Stainless steel||Tribological properties and corrosion resistance|||
|Solution immersion||HA||Mg alloy||Corrosion resistance|||
|Al2O3/TiB2/TiC||Carbon steel||Microhardness and wear resistance|||
|Metal organic chemical vapor deposition||SiO2||Alloys||/|||
|Dip-coating||Na2SiO3/Al2O3||Stainless steel||High temperature oxidation inhibition and corrosion resistance|||
3. The applications of ceramics coated metallic materials
Up to now, the ceramics coated metallic materials have great potential in a wide variety of applications due to its unusual properties, such as good mechanical properties, corrosion resistance, thermal stability, and biological properties. It is worth noted that hydrophobic treatment of ceramic coatings on metallic materials ensuring superhydrophobic surfaces with special surface physicochemistry has recently received much attention in many fields.
It is well known that metallic material is irreplaceable in industrial application. The ceramic coatings bestow numerous unusual properties to metallic materials. Early in 1987, Ceramic coating as thermal barrier coating was tested on turbine blades in a research engine. Today, thermal barrier ceramic coatings are used in a low risk location within the turbine section of certain gas turbine engines . In addition, Qin
Recently, superhydrophobic surface has been extensively developed due to its unique property including corrosion protection, self-cleaning, oil water separation, anti-fouling, anti-icing, and drag reduction . Superhydrophobic ceramic coating was obtained by hydrophobic treatment of ceramic coating with hierarchical rough structure, which greatly expanded the application range of metal materials [64, 65]. In 2020, Emarati
In addition, ceramic coatings have numerous applications in the field of biomedical engineering, mainly because of their biological properties. The bioinert properties of ceramic coatings help them with biocompatibility, and good hardness and wear-resistance properties make them suitable for substitution of hard tissues (bones and teeth). On the contrary, bioactive ceramic coatings such as HA coating have been clinically used onto the metallic implant surfaces combining the mechanical strength of metals and their alloys with the excellent biological properties of ceramics for the enhancement of new bone osteogenesis [70, 71].
Importantly, researching work shows that superhydrophobic surfaces can dramatically reduce the contact between fouling organisms and substrate surfaces exhibiting excellent anti-fouling and hemocompatibility properties [72, 73]. Hu
In this chapter, we introduce and discuss various techniques utilized to fabricate a range of different ceramic coatings on metal materials with desirable properties such as good mechanical property, corrosion resistance, thermal stability, and biological property. It is not surprising that superhydrophobic ceramic coatings on metallic materials can make the materials be attractive for applications in anti-fouling, self-cleaning, corrosion protection, wear resistance, oil/water separation and biotechnology.
This work was supported by the Natural Science Foundation of Jiangxi Province (20192BAB203008).
Conflict of interest
The authors declare no conflict of interest.