zirconium alloys – Zirconium Metal

Coatings and Surface Treatments for Zirconium Alloys

Introduction

Coatings and surface treatments for zirconium alloys are essential for enhancing their corrosion resistance, wear resistance, and biocompatibility. They can also improve performance characteristics for specific applications. Besides, zirconium alloys benefit from additional surface treatments to extend their lifespan and functionality, especially in more aggressive environments or when additional properties are needed.

This article explores various coatings and surface treatments designed for zirconium alloys. Hope that you can learn about their applications and benefits.

1. Anodizing for Zirconium Alloys

Anodizing is a process that electrochemically alters a metal surface to produce a decorative, robust, and corrosion-resistant anodic oxide layer, effectively enhancing the metal’s natural oxide surface layer.

It is most commonly applied to aluminum, but other metals, including zirconium and titanium, can also be anodized. The anodized metal has an increased resistance to corrosion and wear, and it can accept vibrant colors during the process.

These metals have become a popular choice for both protective and aesthetic purposes in various industries, such as automotive, aerospace, consumer electronics, and construction.

1. Thermal Spraying

Thermal spraying is a coating process where melted (or heated) materials are sprayed onto a surface. The coating material, in the form of powder or wire, is heated to a molten or semi-molten state and accelerated towards the target substrate. Thermal spraying creates a strong bond to the surface upon cooling.

This technique is used to apply coatings for a variety of purposes, including protection against wear, corrosion, and heat, and to restore or increase the surface dimensions of components. Thermal spraying encompasses several methods, such as plasma spraying, flame spraying, arc spraying, and high-velocity oxygen fuel (HVOF) spraying.

Each is suitable for different materials and applications ranging from aerospace and automotive to biomedical and electronics.

1. Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD)

Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD) are two advanced techniques for applying thin film coatings onto various substrates.

CVD:

CVD involves chemical reactions between gaseous precursors and the substrate surface. It results in the deposition of a solid material. This method is excellent for coatings that require high purity and uniform thickness, even on complex geometries. It’s useful for semiconductor devices, corrosion-resistant coatings, and high-performance tool coatings.

PVD:

PVD, on the other hand, physically transfers material from a source to the substrate in a vacuum environment. Techniques under PVD include sputtering and evaporation, allowing for the deposition of metals, alloys, and ceramic coatings. PVD coatings are notable for their high density, excellent adhesion, and uniformity, and they are ideal for aerospace components, medical implants, and cutting tools.

2. Electroplating

Electroplating can apply a metal coating, such as nickel or gold, onto zirconium alloys. This process can improve the alloy’s appearance, corrosion resistance, and electrical conductivity. Electroplating is often used in electronic components, decorative items, and applications requiring enhanced conductivity.

3. Passivation

Passivation involves treating the zirconium alloy with a chemical solution, usually an acid, to remove surface contaminants and enhance the naturally occurring oxide layer’s protective qualities. This process improves corrosion resistance by making the surface more passive and less likely to react with its environment. Passivation’s common uses are in the chemical processing industry and in medical device manufacturing.

4. Sol-Gel Coatings

The sol-gel process can create thin, uniform ceramic coatings on zirconium alloys. These coatings can provide excellent chemical stability, corrosion resistance, and thermal protection. Sol-gel coatings are versatile and can be tailored to include various functional materials for specific applications, including optics, electronics, and biomedical devices.

The following table succinctly captures the essence, features, and typical applications of each method. You can check this clear guide to select the appropriate coating process for various requirements.

Methods	Definition	Features	Applications
Anodizing	An electrochemical process enhancing the natural oxide layer for a decorative, durable finish.	Increases corrosion and wear resistance; accepts vibrant colors.	Automotive, aerospace, consumer electronics, and construction.
Thermal Spraying	Coating process spraying melted materials onto a surface.	Provides protection against wear, corrosion, and heat; restores/increases dimensions.	Aerospace, automotive, biomedical, and electronics.
Chemical Vapor Deposition (CVD)	Chemical reactions between gaseous precursors and the substrate, depositing a solid material.	High purity, uniform thickness, suitable for complex geometries.	Semiconductor devices, corrosion-resistant coatings, and tool coatings.
Physical Vapor Deposition (PVD)	Transfers material from a source to the substrate in a vacuum.	High density, excellent adhesion, and uniformity.	Aerospace components, medical implants, and cutting tools.
Electroplating	Applies a metal coating, like nickel or gold, onto substrates.	Improves appearance, corrosion resistance, and electrical conductivity.	Electronic components, decorative items, and enhanced conductivity applications.
Passivation	Treating the alloy with a chemical solution to remove contaminants and enhance oxide layer protection.	Improves corrosion resistance; makes the surface less reactive.	Chemical processing industry and medical device manufacturing.
Sol-Gel Coatings	Creates thin, uniform ceramic coatings.	Offers chemical stability, corrosion resistance, and thermal protection.	Optics, electronics, and biomedical devices.

Conclusion

Coatings and surface treatments for zirconium alloys are critical for enhancing their properties and expanding their application range. By selecting appropriate treatments, it’s possible to significantly improve the performance of zirconium alloys in various industrial, medical, and technological applications.

As technology advances, new coating techniques and materials will likely emerge, further enhancing the capabilities of zirconium alloys. For more information related to zirconium alloys, please check Advanced Refractory Metals (ARM).

Reference:

[1] Mihajlović, Dragana & Cvijović-Alagić, Ivana & Dimic, Ivana & Djokic, Veljko & Rakin, Marko. (2016). Anodization of Ti-based materials for biomedical applications: A review. Metallurgical and Materials Engineering. 22. 129-143. 10.30544/209.

[2] Ahmad, Zaki & Khan, Asad & Farooq, Robina & Saif, Tahir & Mastoi, Naila. (2016). Mechanism of Corrosion and Erosion Resistance of Plasma‐ Sprayed Nanostructured Coatings. 10.5772/64316.

Zirconium Alloys: Unveiling Their Diversity and Applications

Introduction

Zirconium is a lustrous and highly corrosion-resistant transition metal. It finds extensive use in various industries due to its exceptional properties. Zirconium alloys are derivatives of this versatile metal. They are tailored to meet specific industrial demands and offer a range of compositions and characteristics. Here, we delve into the diverse types of zirconium alloys and their applications across multiple sectors.

Types of Zirconium Alloys

1. Zirconium-Copper Alloys (Zr-Cu):

Zirconium-copper alloys combine the corrosion resistance of zirconium with the conductivity of copper. This amalgamation creates materials suitable for electrical applications, such as electrical connectors and conductive components in electronics.

2. Zirconium-Nickel Alloys (Zr-Ni):

Zirconium-nickel alloys exhibit enhanced strength and corrosion resistance. So, they are vital in marine applications, especially for components exposed to seawater. Their ability to withstand harsh, corrosive environments positions them prominently in shipbuilding and offshore structures.

3. Zirconium-Titanium Alloys (Zr-Ti):

Zirconium-titanium alloys boast excellent mechanical properties and high-temperature resistance. They find applications in aerospace engineering, particularly in aircraft components and structural materials, owing to their strength-to-weight ratio and thermal stability.

4. Zirconium-Tin Alloys (Zr-Sn):

Zirconium-tin alloys are known for their exceptional corrosion resistance in acidic and chloride-rich environments. They are extensively utilized in chemical processing industries, such as in the manufacture of heat exchangers and reactors handling corrosive substances.

5. Zirconium-Aluminum Alloys (Zr-Al):

Zirconium-aluminum alloys combine the strength of zirconium with the lightweight properties of aluminum. These alloys find use in the automotive and aerospace sectors, contributing to lightweight structural components that require high strength and corrosion resistance.

6. Zirconium-Niobium Alloys (Zr-Nb):

Zirconium-niobium alloys are also known as Zircaloy. They possess exceptional resistance to corrosion and neutron absorption. These alloys are fundamental in nuclear reactor components, including fuel cladding due to their stability in high-radiation environments.

Applications of Zirconium Alloys

Zirconium alloys stand as pivotal materials across multifaceted industries, owing to their exceptional properties that cater to diverse applications.

–Nuclear Sector

In the realm of nuclear energy, these alloys play a critical role. Their remarkable resistance to corrosion and neutron absorption renders them indispensable in nuclear reactors, particularly for fuel cladding and structural components. This pivotal function ensures the safety and efficiency of nuclear power generation.

–Chemical Processing

Beyond the nuclear sector, zirconium alloys find extensive utilization in chemical processing. Their innate resistance to aggressive chemicals makes them a go-to choice for equipment and machinery in chemical plants, safeguarding against corrosion and ensuring the integrity of processing systems.

–Aerospace and Aviation

In the aerospace and aviation domains, these alloys contribute significantly to the development of lightweight, high-strength components. From aircraft engines to structural materials, zirconium alloys aid in enhancing performance while maintaining durability, crucial for the stringent demands of aviation.

–Marine Uses

Furthermore, in marine engineering, zirconium alloys act as shields against corrosion in harsh marine environments. Their robustness and resilience make them invaluable in shipbuilding and the construction of offshore structures.

The versatile nature of zirconium alloys enables their application across vital industries, where their corrosion resistance, strength, and durability prove instrumental in enhancing safety, efficiency, and longevity in various operational environments.

Conclusion

Zirconium alloys continue to evolve and offer tailored solutions for diverse industrial needs. Their versatility, strength, and resistance to corrosion position them as crucial materials across various sectors. These features also contribute to advancements in technology, engineering, and materials science. As research and development persist, the spectrum of zirconium alloys is expected to expand. They usher in innovations and novel applications in an array of industries.

Advanced Refractory Metals (ARM) is a leading supplier offering a diverse range of zirconium alloys in various sizes and grades. Whether you require specific grades or varying sizes, ARM provides zirconium alloys tailored to your requirements. Please explore our homepage for comprehensive information regarding our zirconium offerings.

Reference:

[1] Zirconium. (2023, December 2). In Wikipedia. https://en.wikipedia.org/wiki/Zirconium

Problems Prone to Welding of Zirconium Alloys at High Temperatures

Zirconium is an expensive corrosion-resistant metal material with excellent resistance to corrosion by acids and alkalis. In some media, it even exceeds metals with good corrosion resistance such as niobium and titanium. Zirconium alloys have been gradually used in recent years as structural materials for equipment and pipelines in the chemical industry due to their good corrosion resistance.

The commonly used zirconium alloy grades include Zr702 (UNSR60702), Zr704 (UNSR60704), and Zr705 (UNSR60705). Among them, Zr702 (UNSR60702) is widely used in chemical projects.

Basic characteristics of zirconium alloy

Zirconium alloy has good welding performance, stable chemical properties at room temperature, and outstanding corrosion resistance. However, its high-temperature chemical properties are lively and have a strong affinity for the pollution of oxygen, nitrogen, and hydrogen in the ambient gas, and dust and humidity in the operating environment. As the temperature rises, its chemical activity sharply increases, and it forms ZrH2 with hydrogen at 200 ℃; it can form ZrO3 with oxygen at 300 ℃; it reacts with oxygen in the air above 550 ℃ to form a porous brittle oxide film; at 600 ° C, zirconium absorbs nitrogen to form ZrN; it absorbs oxygen and severely embrittles the material at above 700 ℃. As the temperature increases, its absorption capacity and reaction speed increase. Therefore, the high temperature environment and welding seams generated by welding are the keys to restrict chemical equipment.

The excellent corrosion resistance of zirconium alloys comes from the oxide film formed on its surface and depends on the integrity and robustness of the oxide film. When zirconium alloy absorbs a certain amount of oxygen, nitrogen, hydrogen and other gas impurities, its mechanical properties and corrosion resistance will drop sharply. Therefore, strengthening the protection of environmental dust, humidity and heat-affected zone surfaces and the back of welds is a key element of quality control during welding.

Problems prone to welding of zirconium alloys

High temperature is the natural enemy of zirconium alloys with great changes in corrosion performance. Zirconium generally reacts easily with the atmosphere at high temperatures. It starts to absorb oxygen at 200 ℃, hydrogen at 300 ℃, and nitrogen at 400 ℃. The higher the temperature, the more intense the reaction. Because zirconium is active against oxygen, nitrogen and hydrogen, it must be protected with a high-purity inert gas or welded in a good vacuum chamber.

During zirconium welding, the weld seam and heat-affected zone are easily polluted by oxygen, hydrogen, nitrogen and other elements in the air, forming hard and brittle compounds, and producing a brittle needle-like structure, which increases the hardness and strength of the welded joint , while the plasticity declines, and the corrosion resistance is also greatly reduced. Therefore, zirconium welding should fully protect the molten pool, weld and heat-affected zone to completely isolate the air.

The welding of zirconium alloys is generally performed by the welding method of tungsten inert gas shielded arc. Other welding methods include electron beam welding, plasma arc welding and resistance welding. Its welding performance is close to that of titanium metal welding. Due to the small thermal expansion coefficient and elastic modulus of zirconium, the welding deformation and weld residual stress are relatively small. It is recommended that the stress relief time of the weld at 1100 ° F (594 ℃) be 1 hour/inch thickness.

Another major problem of zirconium welding is that the weld is prone to soften too much and cause the weldment to be distorted. When welding zirconium, the welding piece should be properly fixed and double-sided welding should be used as much as possible. Except for titanium, niobium, silver, and vanadium, zirconium cannot be directly welded to other metals. Therefore, choosing a clean operating environment and strengthening the isolation and protection of welds and heat-affected zones are the keys to ensuring the quality of zirconium alloy welding.

Stanford Advanced Materials supplies high-quality zirconium alloys to meet our customers’ R&D and production needs. Please visit https://www.samaterials.com/ for more information.

Argon Arc Welding Technology of Zirconium and Zirconium Alloy

Zirconium and zirconium alloys have excellent corrosion resistance to acid and alkali, and even surpass niobium, titanium and other metals in some media. Therefore, zirconium and zirconium alloys are gradually used as structural materials such as equipment and pipelines in the chemical industry with strong corrosion resistance due to their good corrosion resistance in recent years.

Due to the high-temperature chemical activity, zirconium and zirconium alloys can react with various elements in the air at high temperature, thus damaging their mechanical properties. Therefore, in the process of zirconium and zirconium alloy welding, the key to ensuring the quality of welding is to select a clean operating environment and strengthen the isolation and protection of welding seams and parts in the heat-affected zone.

Basic properties of zirconium and zirconium alloys

Zirconium and zirconium alloy materials mainly include R60702, R60704, and R60705. Zirconium and zirconium alloys have good welding properties and stable chemical properties at room temperature. However, its high-temperature chemical properties are very active, and it has a strong affinity for the pollution of oxygen, nitrogen, hydrogen and dust and humidity in the operating environment.

The excellent corrosion resistance of zirconium and zirconium alloys comes from the oxide film formed on the surface and depends on the integrity and firmness of the oxide film. When zirconium and zirconium alloy absorb a certain amount of oxygen, nitrogen, hydrogen, and other gas impurities, their mechanical properties and corrosion resistance will decrease sharply. Therefore, strengthening the protection of the surface of environmental dust, humidity and heat affected area and the back of the welding seam is the key element of quality control in the welding process.

Factors influencing the welding quality of zirconium and zirconium alloy

The tendency of weld cracks

Due to the low thermal expansion coefficient of zirconium and zirconium alloy, the volume change caused by thermal deformation and phase change is very small, and the content of sulfur, phosphorus, carbon and other impurities is very low, there is no obvious trend of cracks in the welding process. However, when the welding seam absorbs a certain amount of oxygen, nitrogen and hydrogen gas impurities, the performance of the welding seam and the heat-affected zone will become brittle. If there is stress in the welding seam, cold cracks will occur.

At the same time, hydrogen atoms have the property of diffusing and aggregating to the high-stress parts in the heat-affected zone with lower temperature, which leads to the formation of relatively weak links in these parts, which may lead to the generation of welding delay cracks.

Selection of welding materials

The filler wire for zirconium and zirconium alloy welding should be selected according to the principle of matching the base material composition. The surface of welding wire shall not have heavy skin, crack, the oxidation phenomenon and metal or non-metal inclusion defects. Besides, the welding wire should be cleaned and dried before use.

Selection of protective gas

Argon arc welding with tungsten electrode of zirconium and zirconium alloy shall adopt high purity argon with 99.999% purity and the impurity content shall meet the requirements of GB/T4842 current standards.

Due to the extremely high requirements on the purity of welding protective gas, continuous gas charging is required during the welding process, and the gas cannot be interrupted in the process; otherwise, argon charging needs to be replaced again. Therefore, the direct gas supply method using ordinary argon in a single bottle cannot meet the protection requirements. It is necessary to increase the gas supply capacity of multiple argon bottles in series and satisfy the simultaneous operation of multiple welders through the air separation cylinder.

Please visit http://www.samaterials.com for more information.