Failure analysis of the impeller of a slurry pump subjected to corrosive wear

A systematic study on the failing impeller of a slurry pump used in wet process phosphoric acid manufacture has been carried out by means of scanning electron microscopy in order to clarify the failure mechanisms. The results show that the weight loss of corrosive wear is affected by the impact velocity and its tangential and normal components in different areas of the impeller. The area where the impact velocity is below the critical value is a uniform corrosive wear area and its weight loss is very small. The area where the impact velocity is above the critical value is a non-uniform corrosive wear area, and its weight loss increases rapidly with the increase in impact velocity. The corrosive wear mechanisms are different from one area to another. In the areas where the tangential component of impact velocity is larger, the main mechanism is of a cutting mode. On the contrary, in the areas where the normal component of impact velocity is larger, the failure mode consists of the formation of microcracks and the removal of second phases. It is proposed that, owing to the existence of a mass of gypsum as abrasive in the slurry, the wear is mainly responsible for impeller failure, although some corrosion effect exists. With a certain corrosion resistance, increasing the wear resistance of materials may be an efficient means to prolong the service life of the impeller.

Keywords

• Corrosive wear; 
• Slurry pump; 
• Failure