Perhaps a silly poochh. Don't know the dimensions of blades but the width of the blade seems shorter than the length of single crystal DMRL is able to grow. Is it possible for them to grow the crystal widthwise from left to right or vice-versa instead of current approach ? Unless the crystallographic orientation along the length of the blade is strictly required but at least it would be single crystal(of different orientation) nevertheless.manum wrote:http://livefist.blogspot.com/2010/08/ka ... ingle.html
Kaveri's Compressor Blades + The Indian Single Crystal Effort
Has thoriated Tungsten (used in electric bulb filaments that shoots to very high temperatures) been tried? The filament in bulb industry is prepared by powder metallurgy and thoria(ThO2) added for dispersion strengthening to prevent creep at high temperatures. Although the material may be susceptible to oxidation unlike bulbs which have inert gas filling but the Powder metallurgy preparation techniques and dispersion strengthening processes could definitely be borrowed from industry without reinventing the wheel.
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On a different note, it should be considered an advantage that the blades are shorter in length in the hot section which means lower toughness requirement compared to blades in the compressor region. In this regard, ceramic blades could be attempted. The idea that ceramics=brittle only is very old now and a lot of progress has been made in the field. Companies like Kyocera can make a knife out of ceramics that can cut as well as a metal blade and can withstand the impact if dropped from 1 or 2 floors height. The only reason it isn't sold is because it's not economically viable. The same company also makes pumps for corrosive chemicals in chemical industry ENTIRELY made out of ceramics, no metal parts !! Even our refractories industries in India have a lot of experience with some of these ceramics. Remember an engineer deliberately dropping Magnesium Carbide(MgC) bricks on the steel rail and show absence of cracks to demo how strong the bricks were even in green(compacted only, by presses) unfired condition during one of those industrial trips to refractory industry. Of course a brick is a lot thicker than a blade but the point was about exploring such materials(MgC, toughened zirconia, tungsten carbide etc) for blade applications.
In long run, if even the front compressor blades could be made out of ceramics then the need for convoluted S-ducts to minimize the frontal RCS would go away. This has big implications for engine thrust requirements for 5th gen fighters and russkies should definitely explore.
If pure ceramics do not help, Ceramic-metal composites should be attempted for the blades. As a crude example a "broom" comprising of DS metal strips protruding from metal base and ceramic powder compacted around the strips and sintered into final blade shape comes to the mind. The ceramic withstands the high temperature and the metal strips give the tough backing.
JMT