A hairline crack on a first-stage blade is invisible from the outside and catastrophic from the inside. Blades run red-hot, spin at thousands of rpm, and live inches from parts that cost as much as a house — so a damage mode caught on a borescope is a scheduled repair, and the same mode missed is a liberated blade and a wrecked hot section. The whole game is seeing it early and knowing what the finding means. OXMAINT AI is the AI-powered maintenance management software that keeps blade inspections on their EOH clock and turns every finding into a tracked repair-or-replace decision.
Gas Turbine · Hot Gas Path · Blade Damage · Borescope & NDT · Repair vs Replace · 2026
Gas Turbine Blade Damage: Detect It, Classify It, Decide
Turbine blades fail in a handful of known ways — cracking, erosion, hot corrosion, coating loss and thermal damage — and each one has a signature a trained eye and the right NDT can catch. This strategy covers how to find damage early and act on it, with the OXMAINT AI maintenance management software keeping every inspection and finding on one record.
1Inspect
→
2Classify
→
3Decide
→
4Act
Tiprubs, oxidation
Leading edgeerosion, FOD
Airfoilcoating loss, corrosion
Root & filletcracks, creep
~8,000 EOH
combustion inspection — liners, nozzles and transition pieces
~24,000 EOH
hot gas path inspection — stage 1–2 blades, coatings and cooling
~48,000 EOH
major inspection — full teardown, rotor and every blade row
Starts > hours
each start adds more thermal-cycle damage than an hour of steady running
The Damage Modes That End a Blade
Blades fail in known ways, and naming the mode is half the diagnosis — each points to a different root cause and a different fix. Learn the signature of each; book a demo to log findings by damage mode in OXMAINT AI.
Cracking & thermal fatigue
Repeated start-stop cycling opens cracks at trailing edges, cooling holes and root fillets — the mode that liberates a blade if missed.
Creep
Sustained load at high temperature slowly stretches the airfoil, closing tip clearances. Irreversible — it sets the blade's real life limit.
Erosion
Airborne particles wear the leading edge and change the airfoil profile, quietly costing efficiency long before it threatens the blade.
Hot corrosion
Contaminants in fuel or air attack the alloy at temperature, pitting the surface and eating into the metal from the outside in.
Coating loss & TBC spallation
Once the thermal barrier coating flakes away, the alloy underneath overheats and burns — a small spall becomes a burned airfoil fast.
Oxidation & thermal damage
High-temperature oxidation and local overheating scale and discolour the surface — often the first visible sign the cooling is compromised.
Detection, From a Glance to the Grain
No single method sees everything — you escalate from the fast and non-invasive to the deep and precise as a finding warrants. Layer them in order and nothing hides; start free and attach each method's result to the blade in OXMAINT AI.
01
Borescope inspection
The workhorse — through dedicated ports an inspector reads cracks, coating loss, rubs and FOD on the first stages without a teardown.
Non-invasive
02
Fluorescent penetrant (FPI)
On removed blades, dye draws out surface-breaking cracks the eye would miss — the standard confirm after a borescope flag.
Surface
03
Eddy current
Finds and sizes surface and near-surface cracks, and reads coating condition, without the mess of a liquid penetrant.
Surface / near
04
Ultrasonic testing
Sends sound into the metal to find cracks and wall-thinning below the surface, including inside cooling passages.
Subsurface
05
Radiography
X-ray reveals internal cooling-passage condition and hidden defects no surface method can reach — the deepest look.
Internal
The Three Inspections, on the EOH Clock
Blade inspections aren't on a calendar — they're on equivalent operating hours, because a start punishes a blade far more than an hour of steady running. The OXMAINT AI maintenance management software counts the right clock; book a demo to track EOH per unit in OXMAINT AI.
~8,000 EOH
Combustion inspection
Liners, fuel nozzles and transition pieces — a borescope-led look at the hardware that shapes the gas before it hits the blades.
→
~24,000 EOH
Hot gas path inspection
Stage 1–2 blades and vanes, coatings and cooling passages come under scrutiny — the inspection that owns blade condition.
→
~48,000 EOH
Major inspection
Full disassembly — rotor, bearings and every blade row examined, repaired or renewed. The deepest and least frequent of the three.
Intervals are typical figures and vary by frame, duty and the maker's guidance — EOH converts fired hours and start count into one damage-weighted number.
A Finding Without a Decision Is Just a Photo.
The value of an inspection is the action it triggers — run on, repair at the next window, or replace now. The OXMAINT AI maintenance management software turns each blade finding into a ranked work order with the EOH, the history and the decision attached, so nothing stops at the report.
From Finding to Decision
Every finding lands in one of three places — leave it, fix it, or retire the blade. Reading the severity right is what separates a planned repair from a forced outage; start free and keep this decision frame on every blade in OXMAINT AI.
Repair or Replace — Reading It Right
The costliest mistakes are the two extremes: scrapping a blade a shop could have saved, or running on one that should have been pulled. Four questions settle most calls; book a demo to attach these to the work order in OXMAINT AI.
Is the mode repairable?
Coating loss, minor cracks and tip wear often are. Creep and a burned airfoil are not — those are replacement, full stop.
How much life is left?
A repair that lasts one interval on a blade near its EOH limit rarely pays — weigh the fix against the hours it buys.
Is the whole row affected?
One bad blade is a repair; the same mode across the row is a set replacement and a hunt for the root cause.
What's the lead time?
New blades and shop slots have long lead times — a decision made at inspection, not at the outage, keeps the unit on schedule.
How OXMAINT AI Runs the Blade Strategy
Detection, intervals and decisions only hold together if they live on one record per blade, not in scattered reports. Here's what the OXMAINT AI maintenance management software brings to the hot section; start free and build your blade-inspection routine in OXMAINT AI.
EOH-based intervals
Combustion, hot gas path and major inspections scheduled on equivalent operating hours, counting starts and fired hours together.
Findings logged by mode
Borescope and NDT results captured by damage mode and blade position, with photos, so a trend is visible across inspections.
Finding to work order
A flagged crack or spall becomes a ranked repair-or-replace job on its own, routed with the severity and history attached.
Trend over EOH
Erosion and coating condition tracked blade-by-blade across hours, so a slow mode is caught before it reaches the limit.
Parts & lead-time planning
Replacement blades and shop slots flagged against the next outage, so a long-lead part is ordered at the finding, not the failure.
Full blade history
Every inspection, repair and replacement kept per blade and row — the record that proves a decision and catches a repeat mode.
“
Our borescope reports used to live as PDFs in a folder nobody opened between outages. The shift was logging each finding by mode and blade position — so the second time the same stage-one blades showed coating loss, we saw the pattern and chased the fuel contamination behind it. Catching the repeat mode, not just the single blade, is what changed our replacement spend the most.
Rotating Equipment Engineer · Combined-Cycle Plant
Frequently Asked Questions
What are the main gas turbine blade damage modes?
The common ones are cracking and thermal fatigue, creep, erosion, hot corrosion, coating loss and TBC spallation, and high-temperature oxidation. Each has a distinct signature and a different fix, which is why naming the mode is the first step.
Start free and log findings by mode.
How is blade damage actually detected?
Borescope inspection is the primary tool — it reads the first stages through ports without a teardown. Flags are confirmed and sized with NDT: fluorescent penetrant, eddy current, ultrasonic and radiography, escalating as the finding warrants.
What are EOH and why count them instead of calendar time?
Equivalent operating hours combine fired hours and start count into one damage-weighted number, because a start cycles the blade thermally far harder than steady running. Inspection intervals are set on EOH for that reason.
Book a demo to track EOH per unit.
When is a blade repaired versus replaced?
Coating loss, minor cracks and tip wear are often repairable; creep and a burned airfoil are not. The call also weighs how much life is left, whether the whole row is affected, and the lead time on new blades.
How often should hot-section blades be inspected?
Typically a combustion inspection near 8,000 EOH, a hot gas path inspection near 24,000 EOH, and a major inspection near 48,000 EOH — though the exact figures vary by frame, duty and the manufacturer's guidance.
Catch the Crack Before It Catches the Hot Section.
Run the inspect-classify-decide-act loop on every blade with the OXMAINT AI maintenance management software — EOH-based intervals, findings logged by damage mode, each one turned into a ranked repair-or-replace work order, and long-lead parts flagged against the next outage. See the damage while it's still a decision, not a failure.
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