Wet shot peening: controlled compressive stress without damage

Turbine blades
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A blade that fails fatigue inspection means a grounded engine, a halted production line, and a rework bill that dwarfs the cost of the process that caused it.

Wet blasting delivers the compressive residual stress that extends fatigue life, while the water flushes debris continuously. The result is a peened surface that is clean, consistent, and free from the surface contamination that dry processes leave behind. As a result of every process variable - pressure, media concentration, gun position, and motion - being monitored and controlled in closed loop, the peening intensity specified by your engineer is the peening intensity the machine holds, cycle after cycle.

Bandsaw blade
Solid carbide tool

How wet blasting peening works in practice

A slurry of spherical media suspended in water is propelled at the component surface under controlled air pressure. The media imparts compressive stress at the point of impact; the water film prevents media fracture, controls the energy delivered per impact, and carries away contaminants without embedding them. Adjusting air pressure, media type and size, gun geometry, and component motion changes the peening intensity achieved, giving engineers a precise and repeatable lever for each component specification.

Typical setup: peening

  • Abrasive: Spherical media specified by the customer or process engineer — typically glass beads, stainless steel shot, or ceramic beads in a size range matched to the target intensity. Media specification is usually held on the process document, not set by the operator.
  • Pressure: Indicative range 3–6 bar (44–87 psi) air pressure; slurry pressure set independently. Higher pressure increases Almen intensity.
  • Guns: Automatic in most production applications. Complex geometries use multi-axis oscillation or 6-axis robotic positioning to keep the blast stream perpendicular to the component surface. Continuous product such as bandsaw blade is processed using a gantry in a Profelis configuration.
  • Minimum recommended control: Closed-loop air pressure control and automatic component motion as a baseline for production peening. Manual operation is viable for development, sample processing, or low-volume surface preparation work.
  • Variables: Higher pressure, larger media, and harder media all increase peening intensity. Blade geometry, aerofoil curvature, and edge sensitivity dictate gun standoff and angle. Recipe shifts are validated against the saturation curve for each new component type.

How Vapormatt controls the wet blasting process

Peening capability: what wet blasting achieves

The parameters shown below are indicative and confirmed for the component types listed. Wet blasting peening handles the full range from precision aerofoil surfaces to continuous industrial tooling.

Component typeTypical size or weightProcess modeAchievable outcomeMinimum control
Aerospace titanium fan blade (Ti-6Al-4V aerofoil)Up to approx. 1.5 m spanAutomatic — turntable with Z-axis oscillationAlmen intensity 15–20N (Type N), 200% coverageClosed-loop air pressure control; automatic motion
Aerospace LPC blade (titanium alloy, multi-stage)Small aerofoil, multi-stage variantsAutomatic — turntable with Z-axis oscillationAlmen intensity 7–13N (Type N), 100% coverage, intensity window held across 13 measurement positionsClosed-loop air pressure control; automatic motion
3D printed tensile test sample (aluminium alloy)Approx. 200 mm x 10 mm x 8 mmManualSurface Ra reduced to 1.5 µm (Almen intensity not the aim of this trial)Basic manual machine
Bandsaw blade (continuous, industrial)70 mm section thickness, continuous coilAutomatic — gantry (Profelis)1500 MPa compressive residual stressClosed-loop air pressure control

 

Titanium fan blade in a Cougar Vertical with Almen strips attached

Proof point - aerospace titanium fan and LPC blades

A Japanese aerospace manufacturer needed to validate wet blasting peening against customer-specified Almen intensity windows for titanium fan blades and multi-stage LPC blades, with 13 Almen strip positions on the fan blade and separate saturation curves required for each blade stage. In Vapormatt sample processing trials using a Sabre machine configured to replicate a Cougar vertical, with glass beads size No.5 at 5–6 bar air pressure and 2.4 bar slurry pressure, all 13 fan blade positions returned intensities within the 15–20N window, and LPC blade stages met their respective 7–11N and 10–13N specifications. Source: Vapormatt sample processing trial TRF-1884.

Wet blasting peening is used across aerospace, industrial tooling, and additive manufacturing post-processing. For sector-specific requirements - including fatigue-critical components in [aerospace applications] and surface integrity demands in [additive manufacturing post-processing] - the process parameters and qualification routes differ. Those pages cover the application in its industry context.

Leopard Cub automatic wet blasting machine

The right machine for your peening application

Profelis - continuous product such as bandsaw blade, where throughput per metre is the primary commercial driver.

Cougar+ - medium to large discrete components, including aerofoil sections up to approximately 1.5 m, where production volume and process control specification are both relevant.

Leopard Cub - very large discrete components where part size is the constraint.

Contact us

Find out if wet blasting peening is right for your components

Talk to a Vapormatt process engineer about your specification

Related machines

Sabre wide
Automatic machines

Sabre automatic wet blasting machine

Five-axis CNC precision cell for high-value components with complex geometries, where conventional automatic blasting cannot deliver the required control. More details
Cougar+ Wide
Automatic machines

Cougar+ automatic wet blasting machine

Robust and highly configurable with 32 options. Built for long production runs across demanding applications, from aerospace peening and cleaning to extrusion die maintenance. More details

FAQs

How do I know the process is hitting my specified Almen intensity window, not just somewhere near it?

Vapormatt machines run saturation curve validation as part of commissioning each new component recipe. Almen strips are placed at multiple positions across the component, process time is doubled at each step until arc height increase falls to 10% or below, and the saturation point is confirmed before a production recipe is locked. The machine then holds that recipe in closed loop. If your specification carries multiple intensity windows for different sections of the same part, each section is validated separately.

Our current process works, but coverage consistency on complex aerofoil geometry is the problem. Can wet blasting solve that?

Coverage consistency on curved or compound surfaces depends on keeping the blast stream perpendicular to the surface as the component moves. Vapormatt machines achieve this through multi-axis component manipulation - turntable with Z-axis oscillation for most aerofoil work, 6-axis robotic positioning for the most complex geometries. In Vapormatt sample processing trials on titanium fan blades, intensity readings across 13 Almen strip positions on a single blade ranged from 15N to 20N, all within the specified 15–20N window.

Can wet blasting peening be validated against a customer-issued specification using standard Almen methodology?

Yes. The process uses standard Type A or Type N Almen strips and gauges. Saturation curves are plotted from the trial data and documented in a test report. If your specification references a particular media standard - for example, CSS 8 VG300 AECMA prEN 2750 for glass beads - the machine can be loaded with conforming media and the trial documented against that reference.

We do low volumes across several different component types. Is the recipe changeover practical?

Each component type has its own stored recipe — media type, pressure, gun position, motion profile — and changeover is a recipe selection, not a re-setup from scratch. For mixed-component production environments, the more relevant question is fixturing: if components share a fixture family, changeover time is minimal.

Does the water carrier affect the peened surface?

The water acts as a cushion and a transport medium, not a reactant. It prevents media fracture, which keeps media geometry consistent and avoids the angular debris that can cause surface contamination in dry processes. A DI water rinse removes residual media and slurry after processing. The surface exits the process clean and ready for inspection or coating without an additional cleaning stage.