Comment effectuer un traitement de surface sur un alliage Hastelloy ?

As a high-performance corrosion-resistant material, the surface state of Hastelloy directly affects its corrosion resistance and service life. Through scientific surface treatment, defects generated during the processing can be eliminated, and the corrosion resistance of the surface can be strengthened to maintain stable performance in extreme environments. For different application scenarios, the surface treatment technology of Hastelloy alloy can be divided into several categories, such as mechanical treatment, chemical treatment, electrochemical treatment, etc. Each method has its unique process characteristics and applicable scope. ​

Mechanical treatment is the fundamental step in the surface pretreatment of Hastelloy alloys, mainly used to remove surface oxide scales, burrs, and machining marks. The commonly used sandblasting treatment uses high-speed abrasive (such as alumina, quartz sand) to impact the alloy surface, which can not only remove the oxide layer but also form a uniform rough surface, creating good adhesion conditions for subsequent coatings or chemical treatments. For components with high precision requirements, polishing treatment is more suitable, which can be divided into two methods: mechanical polishing and manual polishing. It can reduce the surface roughness to an extremely low level, reduce the gaps caused by medium retention, and thus reduce the risk of pitting corrosion. In addition, the rolling process can achieve deburring, brightening, and stress relief simultaneously through the friction between the abrasive and the workpiece, and is commonly used for batch processing of small standard parts. ​

Chemical treatment improves surface properties through chemical reactions, which is a key step in enhancing the corrosion resistance of Hastelloy alloys. Acid washing treatment uses acidic solutions (such as a mixture of nitric acid and hydrofluoric acid) to dissolve surface oxide films, especially suitable for welded components. It can effectively remove oxide scales and welding slag generated in the heat affected zone and restore the corrosion resistance activity of the alloy. Passivation treatment is to place the acid washed workpiece in an oxidizing solution, promoting the formation of a dense oxide film on the surface. This film can block the contact between the corrosive medium and the substrate, significantly improving the ability to resist uniform corrosion and intergranular corrosion. For Hastelloy alloy components that require long-term use in high-temperature environments, chemical oxidation treatment can generate a moderately thick oxide layer that combines oxidation resistance and thermal insulation functions. ​

Electrochemical treatment is suitable for scenarios that require extremely high surface quality and can achieve more precise surface modification. Electrolytic polishing dissolves the micro protrusions on the surface of alloys through direct current, resulting in a mirror like smooth surface. This treatment not only improves the appearance quality, but also reduces the corrosion hazards caused by surface defects. It is commonly used in precision instrument components. Anodizing generates a thicker oxide film on the surface through electrolysis, which is firmly bonded to the substrate and can further enhance wear resistance and corrosion resistance, especially for Hastelloy alloy components used in friction conditions. ​

In practical applications, the selection of surface treatment processes should be based on the alloy model and the operating environment. For example, the C-series Hastelloy alloy used in chemical equipment often adopts a combination process of “sandblasting+pickling+passivation” to cope with strong corrosive media; In the aerospace field, electrolytic polishing is often chosen for components to meet the requirements of high precision and low roughness. It is worth noting that cleaning and protection after surface treatment are equally important, and secondary pollution or mechanical damage should be avoided to ensure the long-term stability of the treatment effect. Through reasonable surface treatment techniques, the performance potential of Hastelloy alloys can be fully utilized, providing reliable material guarantees for extreme working conditions in various industries. ​