The coating production process can be likened to the creation of an artwork, with all steps, including pre-treatment, spraying and post-treatment, contributing to the final result. Imperfection in even one of these steps will lead to a failed product. In many cases, the problems are insidious, it might just be a slight increase in the torque required for valve operation. Spraying is the most critical link in the process. A proper spraying process shall be as precise and stable as possible. Spray is a process of material addition that must be controlled carefully. Just like machining, state-of-the-art equipment is not the only factor to consider; suitable fixtures and years of experience are also crucial. Stability is all about process management; once a perfect spraying process( pre-heat, speed, distances, etc.) is achieved, it is essential to ensure that all these steps are implemented in future with minimum intervention. To be more cost-competitive, some manufacturers still use manual spraying; however, this approach is not recommended as it is neither precise nor stable. Heat treatment refers to the fusing step in the Spray & Fuse coating process. Valve users increasingly accept Spray & Fuse coating as π www. valve-world. net Valve World August 2025 39
SEVERE SERVICE
to withstand abrasive, erosive, highpressure, and high-temperature conditions or exposure to solids, the right choice and quality of base material and coating will impact performance such as tightness, endurance, torque and repairability of the valve.
Image 2: High-precise coating
General problems in severe service conditions
The harsh conditions in severe service environments are a challenge for the lifetime and sealing performance of the valve ball and seat. Only with a suitable material selection can the premature performance loss of the valve be avoided. High-pressure and high-temperatures, combined with solids, can lead to galling or even chipping and destruction of the coating. This may result in increased torque and a nonoperable valve and / or a high leakage rate. The same applies to corrosion, erosion or abrasion when the wear resistance of the coating is not adequate.
Image 3: Vacuum furnace
Image 4: Smooth checking
Recommended solutions
HVOF and Spray & Fuse coatings are two commonly used coatings in the valve industry. The advantages and applications of these two coatings( regardless of powder material) are shown in Table 1.
What makes a good coating?
The coating production process can be likened to the creation of an artwork, with all steps, including pre-treatment, spraying and post-treatment, contributing to the final result. Imperfection in even one of these steps will lead to a failed product. In many cases, the problems are insidious, it might just be a slight increase in the torque required for valve operation. Spraying is the most critical link in the process. A proper spraying process shall be as precise and stable as possible. Spray is a process of material addition that must be controlled carefully. Just like machining, state-of-the-art equipment is not the only factor to consider; suitable fixtures and years of experience are also crucial. Stability is all about process management; once a perfect spraying process( pre-heat, speed, distances, etc.) is achieved, it is essential to ensure that all these steps are implemented in future with minimum intervention. To be more cost-competitive, some manufacturers still use manual spraying; however, this approach is not recommended as it is neither precise nor stable. Heat treatment refers to the fusing step in the Spray & Fuse coating process. Valve users increasingly accept Spray & Fuse coating as π www. valve-world. net Valve World August 2025 39