Deposition efficiency (DE) is defined as an idealized measure of the percentage of particles introduced into a spray jet that actually deposits onto a flat substrate without overspray considerations. Deposition efficiency can be measured according to the following procedure:

•Determine the mass (X) of a clean, grit blasted 4 in. × 6 in. × 0.125 in. (100 × 150 × 3 mm) flat steel plate

•Place a known mass of powder into the powder feeder

•After stabilizing the spray parameters and powder feed, spray material onto the steel plate for a known period of time (e.g., 60 s) at a predetermined feed rate (e.g., 20 g/min) ensuring that the spray pattern remains on the plate at all times. (The plate may be cooled as necessary using air/gas jets directed at the rear face of the plate.)

•Measure the mass (Y) of the plate plus the coating.

•Determine the gain in mass (Z) due to the coating deposited (Z = Y - X).

•Divide the mass deposited in one minute (Z) by the powder feed rate and multiply by 100 to give DE in %.

•Repeat the measurement a minimum of three times and take the average.

Related terms: target efficiency, sticking efficiency.

Notes:
1). A scale capable of measuring to an accuracy of 0.1 g should be used to measure the changes in mass.
2). Deposition efficiency is only useful insofar as it provides a measure for optimizing spray parameters.
3). When substrate geometry, size, and overspray are taken into consideration, the ideal DE decreases substantially, yielding a true deposition efficiency, properly termed target efficiency (TE).

Reference: Handbook of Thermal Spray Technology, Ed. J.R. Davis, ASM International, Materials Park, OH, 2004.

Source: Dr. Richard Knight, FASM, Auxiliary Professor and CPPM Director, Drexel University, Philadelphia, Pa.

TSS Regional Events

Aerospace Coatings Symposium
October 15-16 2008
Sheraton Bradley Hotel, Bradley (Connecticut) International Airport
Learn about some of the latest developments in thermal spray and other surface engineering technologies designed specifically for use in the aerospace industry.

Pre-Event Seminar
Materials and Processes for High Temperature Gas Turbine Components
October 13-14, 2008
Sheraton Bradley Airport
Instructor: Dr. Donald Boone, President, BWD Turbines Ltd., Walnut Creek, Calif.
Seminar focuses on thermal spray and other surface modification processes critical to the aerospace industry.

Symposium on Improving Reliability and Consistency in Thermal Spray
December 2-3, 2008
Hyatt Regency Montreal, Quebec, Canada
Presentations by invited speakers covering reliability and consistency of thermal spray processes and coatings, and poster session.

Sponsorships Available for Both Events
To learn more about tabletop exhibiting and sponsorship opportunities, or to discuss customizing a program to meet your specific needs, contact Kelly Thomas, Exposition Sales Manager (440-338-1733)