Polishing Inconel Parts: Tips and Techniques

Inconel is a family of austenitic nickel-chromium-based superalloys. These alloys are known for their excellent resistance to high temperatures, corrosion, and mechanical stress. Inconel parts are widely used in aerospace, automotive, and other high-performance applications. However, polishing Inconel parts can be a challenging task due to the unique properties of these alloys. In this article, we will discuss some tips and techniques for polishing Inconel parts.

Ceramic media is a non-abrasive media that can produce a fine finish on Inconel parts. Ceramic media is available in various shapes and sizes, such as cylinders, triangles, and balls. The shape of the media can affect the polishing action and the surface finish. For example, cylindrical media can reach tight spaces and corners, while spherical media can produce a more uniform finish.

Steel shot is an abrasive media that can remove the oxide layer on Inconel parts more efficiently than ceramic media. Steel shot is available in different sizes, ranging from fine to coarse. The size of the media should be chosen based on the surface finish requirements and the part geometry. Larger media can produce a rougher finish but can also remove surface imperfections more quickly.

Using a lubricant is important for polishing Inconel parts. Lubricants can reduce friction and heat during the polishing process, which can prevent damage to the surface of the Inconel. Lubricants can also help to carry away the removed material and prevent it from embedding in the media.

Water is a common lubricant for vibratory finishing machines. However, water can also cause corrosion on Inconel parts if they are not dried immediately after the polishing process. Therefore, it is recommended to use a rust inhibitor in the water to prevent corrosion.

The process parameters, such as the speed and amplitude of the vibratory finishing machine, can have a significant impact on the quality of the finish. It is important to choose the right parameters for the specific Inconel part being polished.

The speed of the vibratory finishing machine should be chosen based on the size and weight of the Inconel part. Higher speeds can produce a more aggressive polishing action, but they can also cause excessive wear on the media and the machine. Lower speeds can produce a finer finish but may require a longer processing time.

The amplitude of the vibratory finishing machine determines the intensity of the polishing action. Higher amplitudes can produce a more aggressive polishing action but can also cause excessive wear on the media and the machine. Lower amplitudes can produce a finer finish but may require a longer processing time.

Polishing Inconel parts may require multiple stages, using different media or lubricants, to achieve the desired finish. The first stage can use an abrasive media, such as a steel shot, to remove the oxide layer and any surface imperfections. The second stage can use a non-abrasive media, such as ceramic media, to produce a fine finish. Lubricants can also be changed between stages to optimize the polishing action.

After polishing the Inconel parts, it is important to check the surface finish to ensure that it meets the desired specifications. The surface finish can be measured using a surface roughness tester or a profilometer. The surface roughness is typically measured in Ra (arithmetical mean roughness) or Rz (ten-point mean roughness) values.

If the surface finish does not meet the desired specifications, the process parameters can be adjusted or the polishing process can be repeated. It is important to note that over-polishing can also degrade the surface finish and cause surface defects, so it is important to monitor the polishing process carefully.

Polishing Inconel parts can be a challenging task, but with the right techniques and equipment, it is possible to achieve a high-quality finish. Choosing the right media, using a lubricant, optimizing the process parameters, considering multiple stages, and checking the surface finish are all important factors for successful Inconel polishing. By following these tips and techniques, you can achieve a smooth and uniform finish on your Inconel parts, which will enhance their performance and durability in high-stress applications.