Development of 1232℃(2250°F)erosion and impact tests for thermal barrier coatings

摘要

High temperature erosion and impact tests were developed for evaluation of thermal barrier coating(TBC) systems that are being generated for the High-Speed Civil Transport supersonic aircraftunder NASA's Enabling Propulsion Materials program. The TBC-coated test specimen is a 6.1-mm(0.24-inch) diameter cylindrical pin. Twelve pins are mounted on a carousel with a pitch diameter of46 mm (1.813 inch). This carousel is rotated at 500 rpm, 50 mm (two inches) from the combustorexhaust of a burner rig, while the TBC temperature is controlled at 1232℃ (2250°F) using apyrometer. The particulate is injected radially into the combustor in two horizontally opposedpositions. Two separate types of particulate are used in the tests: 50-micron and 560-micron crushedalumina. The effects of the 50-micron erosion and 560-micron impact tests are quite different, but ineach case excellent similarity is seen between damage to test specimens and that of commercialengine service hardware. The temperature of the impinging particulate is above 1450℃ (2642°F), and the particulate velocities were determined to be 174 and 9 meter/second (570 and 30feet/second), respectively, for the 50-micron and 560-micron materials. A mathematical expression was developed for erosion wear as a function of particle size,velocity, hardness and density. inc ranges over which these parameters were varied are particle size10 to 180 micron, velocity 107 to 332 meter per second, hardness 820 to 2100 kg/mm{sup}2 Knoop,density 2.2 to 5.7 gram/cc. Erosion wear is linear with the accumulated mass of eroding particulateused. Impact wear caused by 560-micron alumina is distinctly nonlinear.