Wet blasting is a proven solution for heat scale removal, advantages include:
• Effective oxide layer removal - Heat scale consists of tenacious chromium and nickel oxides on superalloy surfaces. Wet blasting's controlled impact energy effectively breaks the oxide-to-metal bond while the water flushes away loosened scale particles, preventing re-deposition.
• Preservation of base metal properties - Heat scale removal must not alter the underlying material's fatigue properties. The water cushioning effect of wet blasting does not affect the substrate, maintaining the original stress-relieved condition critical for turbine components operating under cyclic loading.
• Selective scale removal - Wet blasting can remove heat scale while leaving beneficial surface treatments like wet shot peening or controlled surface textures intact. This selectivity is crucial for components like compressor blades where the base surface condition affects aerodynamic performance.
• Post-heat treatment surface restoration - After heat treatment processes that create scale, wet blasting restores the original surface finish without introducing new residual stresses that could affect fatigue life or dimensional stability.
• Preparation for critical coatings - Heat scale interferes with thermal barrier coating adhesion on turbine components. Wet blasting removes scale completely while creating the optimal surface roughness for coating bond strength without over-roughening that could cause coating stress concentrations.
• Internal passage cleaning - For hollow aerospace components with internal cooling passages, wet blasting media can navigate complex geometries to remove scale buildup that would restrict airflow and reduce cooling efficiency.
• Metallurgical integrity - Unlike chemical descaling that can cause hydrogen embrittlement or intergranular attack, wet blasting is a purely mechanical process that maintains the base metal's microstructure and corrosion resistance properties.
• NDI compatibility - The clean, uniform surface after wet blasting is ideal for subsequent non-destructive inspection methods like fluorescent penetrant inspection or eddy current testing required in aerospace quality control.
