The document discusses a compressor blade failure analysis. It notes that the blade failed due to fatigue originating from machining marks at the blade hub-stem junction on the leading edge side. Nickel-based blades are now commonly used instead of earlier cobalt-based blades, as nickel-based blades can withstand higher temperatures and have a longer lifespan, though cobalt blades previously had an even longer lifespan. The analysis procedure described examines blade microstructure and composition at different sections to determine the failure cause.

1. Ashutosh Kannawar
SKNCOE (Vadgaon)
TE Mech -2
SEAT NO:T120360925

2.  Propulsion system
 compressor
-Draw air&compress&deliver in combustion
chamber

3.  Aerodynamics
 Mechanical
 Thermal load
 Design ,Manufacturing
 Material selection
 Assembly etc
COMMON MODE OF FAILURE:
-Fatigue failure

4.  After disassembling the engine after a test run
 Take blade &analyse it, using visual&stereo binocular
method
 Stereo zoom microscope is used

5.  Fracture from hub region at leading edge
 Crack extends from fracture to centre of aerofoil
section
 Fatigue failure
 Crack origin near junction of the airofoil &stem region
at leading edge side

6. Blade Failure Pattern

7.  Machining marks
 Creates stress
concentration
 So fatigue crack
occur

8.  Compressor blade found to have failed in progressive
mode i.e.by fatigue
 Crack originate at blade hub-stem junction at the
leading edge side
 Presence of machining cracks is reason for failure

9.  To avoid stress concentration avoid machinig marks
 Avoid abrassive marks

10.  What are the blades:individual component which
makes turbine section of gas turbine & blades extract
energy from gas produced by combuster

 Different materials are used like nickel ,cobalt
 disadvantage of it :more complicated &costly.also
system must be strong to resist high pressure

11.  Desirable properties:corrosive resistant ,strong
 -cobalt (earlier used )
 -nickel (most common)
 Previosly cobalt is used

12.  Life is measured in hours before failure of blade
 Cobalt based blade have 50,000 hrs life
 Nickel based blade have 15,000 hrs life
 Also nickel based blades can work at high
temperature


13.  Failure cause :
 -microstructural changes
 -void formation
 -environmental effect
 Chemical damage

14.  Equipment –optical emission spectrometer
 EDS analyzer
 Three sections method(transverse)
 1)at root
 2)mid point
 3)top of airofoil


15. PROCEDURE:
 1)Take a blade which is failed
 2)Apply three sections method
 3)Put the blade below optical emission spectrometer
 4)Observe microstructure

16.  Hardness increases as we move towards fracture
 Ductility of the blade decreases due to high
temperature
 Chemical compossition of blade is same as IN-738LC
super alloy

17.  Gamma phase dissolve & disapper with increasing
distance from root
 Crack growth is interdendritic
 Hardness increases in fracture zone