US Army Corps
of Engineers
Construction Engineering
Research Laboratories

USACERL Technical Report 97/118
July 1997

Construction Productivity Advancement Research (CPAR) Program

Cavitation- and Erosion-Resistant

Thermal Spray Coatings

by

Jeffrey H. Boy, Ashok Kumar,
Patrick March, Paul Willis, and Herbert Herman

Approved for public release; distribution is unlimited.

A Corps/Industry Partnership To Advance
Construction Productivity and Reduce Costs

SF298

Backup Abstract

This study demonstrated the effectiveness of thermal spray cavitation- and erosion-resistant metal coatings for hydroelectric and utility plant turbines and pumps. Of 21 thermal spray coatings tested, Stellite® 6 applied by the high-velocity oxyfuel (HVOF) process had the lowest cavitation rate (11.7 mg/h). This was higher than the corresponding rate of 3.2 mg/h for 308 stainless steel weld reference. In slurry erosion wear testing, the volume loss for HVOF-applied Stellite® 6 was 5.33 mm³/h, much lower than volume losses for 304 stainless steel and A572 carbon steel. The field applicability of Stellite® 6 was successfully demonstrated on a hydroelectric pump/turbine.

Stellite® 6 deposited by the HVOF process should be considered for repair of damage resulting from erosion and subsequent cavitation caused by surface roughening. Stellite® 6 coatings should also be considered for the mitigation of galvanic corrosion. Damage caused by direct cavitation should be repaired by welding. Advanced iron-based alloys such as NOREM®, D-CAV®, CaviTec®, and Hydroloy® should be considered for use due to their superior cavitation resistance. The use of thermal spray coatings such as HVOF-applied Stellite® 6 should also be considered for repair of pumps subjected to erosion and subsequent cavitation caused by surface roughening.

Foreword

This study was conducted for the Directorate of Civil Works, Headquarters, U.S. Army Corps of Engineers (HQ USACE) under Construction Productivity Advancement Research (CPAR) Work Unit 3121-LY4, "Development of Cavitation/Erosion-Resistant Thermal Spray Coatings." The technical monitors were A. Wu, CECW-EE, and C. Chapman, CECW-OM.

The work was performed by the Materials Science and Technology Division (FL-M) of the Facilities Technology Laboratory (FL), U.S. Army Construction Engineering Research Laboratories (USACERL) in partnership with the Thermal Spray Laboratory at the State University of New York (SUNY) at Stony Brook. Flame Spray Industries, Fort Washington, NY, was a participant in the research. The USACERL Principal Investigator was Dr. Ashok Kumar. Dr. Jeffrey H. Boy is at USACERL under a postgraduate research program through the Oak Ridge Institute for Science and Education, Oak Ridge, TN. Patrick March is Manager, Engineering Laboratory of the Tennessee Valley Authority (TVA), Norris, TN. Paul Willis is with the USACE Hydroelectric Design Center (CENPD-PE-HD), Portland, OR. Dr. Herbert Herman is the director of the Thermal Spray Laboratory at SUNY Stony Brook. Thermal spray samples were prepared by the Zatorski Coating Co., East Hampton, CT, and weld samples were prepared by Robert A. Weber, CECER-FL-M. The field demonstration was conducted at the TVA Raccoon Mountain pumped-storage hydroelectric plant, Chattanooga, TN, with the cooperation of Mitch Burress, Wayne James, and Leon Hicks. The draft Civil Works Guide Specification was prepared by Steve Dingman, U.S. Army Engineer District, USACE Portland. Sam Testerman, Portland District, reviewed the safety and occupational health elements of the report. Dr. Ilker Adiguzel is the Acting Chief, CECER-FL-M, and Donald F. Fournier is Acting Operations Chief, CECER-FL. The USACERL technical editor was Gordon L. Cohen, Technical Information Team.

Dr. Michael J. O'Connor is the Director of USACERL.