What are the disadvantages of using Stelloy cladding technology for the internal components of control valves?
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Looking at the Wuzhong sample, the notes regarding the internal components of the control valve state that it is not recommended to use Stellite for welding these components. What are the disadvantages of this welding process? The material of the sample valve spool is 420, 1.4021, or 3Cr17NiMo, which is hardened or nitrided. Is it because of the concern that the hardened material and the valve core material are different and might cause detachment?
Since Stellite has a different material composition from that of the valve core, in environments with large temperature variations, the weld-on alloy layer is prone to cracking and peeling off.
Explain 2 issues: 1. Wu Zhong does this to save costs. 2. Wu Zhong’s surfacing process is substandard. 420 is a martensitic steel; we don’t refer to it as stainless steel. Generally, when using martensitic steel, there is no need for surfacing welding, as it already has high hardness, and ordinary heat treatment is sufficient. However, martensitic steel has poor corrosion resistance and tends to rust easily. Therefore, when certain corrosion resistance is required, it is best to use 316+ surfacing.
Be careful, Wu Zhong might cause you trouble. . . :lol
Stellite cladding offers high hardness but is prone to cracking; it is a technically challenging process. Machining the surface after cladding is also difficult. This method is used primarily for enhancing wear resistance. Recently, our company manufactured a batch of components in which the inner cavity of the valves was clad using WCB as the base material. Currently, the cladding thickness is 3 layers, with a maximum of 4 layers allowed, and the surface is then finely machined to a thickness of 2 layers.