What are the most common causes of gas path damage and their possible affects upon future operation?

the main factor is the quantity of fuel being injected & burned

What are the most common causes of gas path damage and their possible affects upon future operation?

The most common causes of gas path damage and their possible affects upon future operation are two major life parametersand damage

Life parameters

The two major life parameters are:

• Time between overhauls (TBO)
• Cyclic life (also called low cycle fatigue life): this is the number of times    the engine is started, accelerated to full power, and eventually shut down, between overhauls.

The most common limited Time between overhauls (TBO) and damages the items of gas path:

• Design life has elapsed.
• Calculations predict life exhaustion.
• Service time has reached some arbitrarily chosen fraction of calculated or experimental failure life.
• Previous failure statistics indicate high probability of failure.
• Frequency of repair renders continued operation uneconomical.
• Nondestructive  inspection reveals cracking.
• Surface degradation from corrosion, including coating degradation, is excessive.
• Grain-boundary attack and/or pitting by oxidation/hot corrosion are excessive.
• Foreign object damage is severe.
• Destructive sampling and testing indicate life exhaustion.
• Excessive deformation has occurred due to creep, causing distortion and unfavorable changes in clearances.
• Sudden and complete fracture occurs.

Definition of Damage, Life, and Failure Criteriaof the items of gas path:

In any component, the failure criteria need to be defined and established. Failure does not always involve fracture or rupture. Progressive damage of rotating blades and high-temperature components under operating conditions leads to exhaustion of life, thus leading to failure. Damage may be defined as a “progressive and cumulative change acting to degrade the structural performance of the load-bearing component or components that make up the plant”.

Life may be defined as the “period during which a component can perform its intended function safely, reliably, and economically”.

With some modifications, the last definitions used in gas path components can be used to define failure and life of elevated-temperature components; that is, component life is exhausted when not use the typical coatings for high-temperature applications involve an oxidation resistant coating and a thermal barrier coating (TBC) and not use less creeping materials has lead to creep, causing distortion and unfavorable changes in the geometry of the airfoil items clearances lead to Performance degradation.

The coating degradation in casing, liner, combustion chamber and theairfoil items surfaces coating

After the airflow has passed the diffuser, it is split up by the liner. One part of the airflow goes through the region between the liner, the casing and the combustion chamber gas path when the coating degraded at the surfaces of them will be causing at the failure mechanism end distortion and unfavorable changes in the geometry of the airfoil items clearances lead to Performance degradation