Evaluation of Erosion Wear of Turbine Steels in Hydropower Plants

Abstract

Slurry erosion in hydro power plant turbine steels has proved to be a great problem from a long time. It mainly occurs due to the suspended sand particles in water which flows through the turbines of the hydro power plants which erode material of the turbine. This problem mainly occur due to heavy rainfalls specifically in monsoons days when a lot of sand particles come along the water. To reduce slurry erosion it is necessary that some protective measures must be taken. So the need of the day is to manufacture the turbines with steels which resist slurry erosion to a great extent. Stainless steels have served a good purpose in this field and proved to be one of the best materials in this case. Moreover coatings done on the stainless steels prove the most effective method in improving resistance to slurry erosion. The main aim of this work was to study the wear behaviour of different stainless steels with and without coatings in a slurry erosive environment. For this purpose three grades of stainless steels 304, 316 and 420 were used as substrate materials. A slurry of water and sand was prepared for this test. These were tested on a slurry pot tester with parameters of concentration 30 % and 50 %, speeds 1000 rpm, 1150 rpm, 1300 rpm and 1450 rpm of the rotating spindle and time at 80, 130 and 180 minutes on coated and uncoated samples. To improve the performance of these steels further these were coated with WC-17Co and Cr2O3 by the thermal spraying method of HVOF. The XRD and SEM analysis was also carried out on the eroded and uneroded samples. After the tests it was concluded that the coated samples resisted erosion greater than the uncoated samples. Performance of WC-17Co coatings proved to be the best