Abradable Coatings

Abradable coatings are used in the aerospace and turbomachinery industry to increase efficiency and fuel savings in various rotating applications. Axial III abradable coatings can be applied with consistent quality at high feed rates and deposition efficiencies. Tests have shown that the Axial III feed rate for spraying AlSi-Polyester can be dramatically increased with no detrimental effects on the coating microstructure. By coupling two powder feeders in parallel, a feed rate of 190 g/min was achieved. In one application, an internal surface of a cone section nominally 750 mm in diameter was sprayed in this configuration and an overall deposition efficiency of 82% was maintained with no change in the coating hardness or porosity.

		Spray Rate: 80-100 g/min Deposition Efficiency: 68% Hardness R15Y: 60-75
Aluminum Silicon Boron Nitrate
		Spray Rate: 80-150 g/min Deposition Efficiency: 90% Hardness R15Y: 65-75
Aluminum Silicon Polyester

 

Product Rate Comparison

	Axial III	Radial Systems
Deposition Efficiency	90 %	60%
Powder Sprayed	11.11kg	16.67kg
Powder on Part	10kg	10kg
Powder Wasted	1.11kg	6.67kg
Deposition Time	159 min	333 min
Feed Rate	70gm/min	50gm/min

 

Cost Comparison

The Mettech Axial III is being used to spray a variety of abradable materials. One material of particular interest is AlSi-Polyester. Mettech has developed the Axial III system to spray AlSi-Polyester with a coating hardness ranging from R15Y 67-72, with a deposition efficiency of 90%. This compares very favourably with radial systems where efficiencies are approximately 55%.

A simple cost comparison shows dramatic savings with the Axial III system during AlSi-Polyester spraying at 90% efficiency. This is compared to radial systems given a deposition efficiency of 60%. The powder savings are described below for this case study with 10 kg of material sprayed on the part:

	Axial III	Radial Systems
Deposition Efficiency	90 %	60%
Feed Rate	70gm/min	50gm/min
Powder Cost	$190/kg	$190/kg
Powder Sprayed	11.11kg	16.67kg
Powder on Part	10kg	10kg
Powder Wasted	1.11kg	6.67kg
Deposition Time	159 min	333 min
Water Powder Cost	$211	$1267
Total Powder Cost	$2,111	$3,167
Powder Savings	$1055 33%