Turbine blade colour change

[rexbo]

hello,

I have a question for anybody willing to help me.

There has been rub against the shrouds, which eroded the blade tip. The blade material is nickel alloy and they are platinum-aluminide coated. Why has the surface blade turned blue (specially on the convex side, and close to blade root)?

thank you

 

[GraviMan]

'Cos it got very hot! Motor bike exhausts do the same thing. Not sure specifically about platinim-aluminide coating. Are you sure the blade din't get hot then creep? Tip clearances only really disappear for that reason.

Are you flying the engine? My guess (I'm not an expert) is that if the blade got hot enough to change colour, or has crept to the point of eroding the tip, it's had it...

Mart