The Application of Hardening Treatment in Industrial Valves

Hardening treatment is a crucial surface engineering technique used to enhance the wear and fatigue resistance of industrial valves while maintaining their internal toughness. This process not only improves the performance of valves but also extends their service life, especially in demanding operational environments. This article explores the application scenarios of hardening treatment, the types of wear it addresses, and specific hardening methods used in industrial valves.

Application Scenarios for Hardening Treatment

The application of hardening treatment is extensive, particularly in industrial environments that demand high wear resistance and reliability. Below are some key application scenarios that illustrate the importance of hardening treatment for valve performance.

1. High Temperature and High Pressure Environments

In industrial settings where fluid temperatures can reach 300°C and the pressure differential across the valve is at least 1.5 MPa, hardening treatment is necessary for the valve internals. These conditions pose significant challenges to the heat resistance and strength of valve materials. Hardening treatment can substantially enhance the wear resistance of valves, ensuring stable operation in high-temperature and high-pressure environments.

2. Presence of Solid Particles

In fluids containing solid particles, the surfaces of industrial valve internals also require hardening treatment. Solid particles can cause wear on the valve, leading to decreased performance. Hardening treatment effectively resists wear caused by these particles, thereby prolonging the valve's service life.

3. Cavitating Media

In applications involving flashing, cavitation, or severe cavitation, surface treatment of the valve internals is essential. These phenomena can lead to rapid evaporation of liquids and bubble formation. The collapse of these bubbles generates shock forces that can severely damage the valve. Hardening treatment helps industrial valves better withstand damage caused by cavitation.

4. Long-Term Harsh Working Conditions

Even under normal temperature and pressure, industrial valves operating in harsh environments (such as chemical corrosion or extreme temperatures) for extended periods, or requiring high precision with low leakage at the seat, should consider hardening treatment. Valves exposed to severe conditions are susceptible to wear, fatigue, and corrosion, and hardening treatment offers additional protection.

Types of Wear and Their Impact

Industrial valve internals are directly exposed to fluids, making them vulnerable to erosion and corrosion. Wear can be classified into the following categories.

Particle Wear: Caused by solid particles impacting the surface, typically occurring in fluids containing solids.
Cavitation Wear: The formation and collapse of bubbles create shock forces that damage the valve surfaces.
Corrosion Wear: Chemical reactions between the fluid and valve materials result in gradual material loss.
Impact Wear: Caused by rapid fluid flow or shocks, commonly seen in high-velocity media.
When selecting industrial valves, it is crucial to address these wear types through surface hardening treatment. Effective hardening can significantly reduce wear on valve internals, enhancing their reliability and lifespan.

Hardening Treatment Methods

Choosing the right hardening method is essential for improving an industrial valve's wear resistance and longevity. Different techniques offer various advantages, making them suitable for specific working environments and performance requirements. Here are some common hardening methods and their characteristics.

1. Carburizing

Carburizing is a process that increases the carbon content on the surface of valve internals. After quenching, the surface hardness can reach HRC 55-65, while the core retains a lower carbon content for good toughness. Carburizing enhances wear resistance and improves contact fatigue strength, enabling valve internals to perform well under various conditions.

2. Nitriding

Nitriding creates a layer of hard, corrosion-resistant nitrides on the surface of steel. After nitriding, the surface hardness of valve internals can reach HRC 65-72, which is higher than carburizing and significantly improves wear and corrosion resistance. This treatment is suitable for industrial valves that must withstand chemical corrosion and high wear.

3. Hard Chrome Plating

Hard chrome plating is a common hardening treatment for valve internals. Chrome hardness can reach 800-1000 HV and offers excellent passivation properties. In the atmosphere, the chrome layer can quickly passivate, providing additional protection. The advantages of hard chrome plating include high hardness, good wear resistance, and excellent reflectivity, withstanding temperatures up to 700°C. This method is often used for wear-resistant industrial valves, such as metal ball valves.

4. High-Velocity Oxygen Fuel (HVOF) Spraying

The HVOF spraying process achieves hardness levels of 60-70 HRC and provides excellent bonding strength. The coating thickness is usually between 0.3-0.4 mm. This technique is primarily used for large-area hardening of industrial valve surfaces and is widely applied in thermal power plants, petrochemical industries, and coal chemical industries involving high-viscosity fluids with dust and solid particles, as well as highly corrosive media.

5. Thermal Spraying

Thermal spraying is a technique that involves heating metal, alloy, or ceramic powders to a molten or highly plastic state and then spraying them onto a pre-treated surface to form a strong bond. This technology effectively enhances wear resistance and service life, making it suitable for various industrial applications.

Conclusion

Hardening treatment is an essential measure for improving the performance of industrial valves and significantly extending their service life, particularly in harsh environments. By selecting the appropriate hardening method based on specific working conditions, it is possible to enhance the wear resistance, corrosion resistance, and reliability of valve internals, ensuring safe and stable operation under complex conditions. With proper design and maintenance, hardening treatment will provide robust support for the long-term use of industrial valves.