1999 Thiokol Paper on Erosion of Steel Substrate Exposed to Ultra-High Pressure Waterjet
The 1999 WJTA paper by Swenson and Miller of Thiokol “EROSION OF STEEL SUBSTRATES WHEN EXPOSED TO ULTRAPRESSURE WATERJET CLEANING SYSTEMS “ is a good summary of the substrate change.
My thoughts on this:
The first pass of a UHP WJ removes some material. I have always thought, as I have looked at micro-photographs, this first-pass removal would be the hackles and/or any embedded abrasive material from the original profile. Then the second or third pass doesn’t remove any additional material. Thiokol has a very minimal tolerance for removal.
Let me summarize what the table shows:
One pass, 36,000 psi, 0.015 mil (0.000015 inch) maximum erosion
Two passes, 40,000 psi, 0.021 mil (0.000021 inch) maximum erosion
Three passes, 40,000 psi, 0.021 mil (0.000021 inch) maximum erosion
Six passes, 40,000 psi, 0.021 mil (0.000022 inch) maximum erosion
One refurbishment, zirconium silicate grit, 0.70 mil (0.0007 inch), erosion
The abrasive blast removal is 0.7 mils; the UHP WJ removal is <0.02 mils.
Their findings are:
The level of material erosion is decreased by approximately 98% when UHP WJ is used compared to abrasive blasting.
All the papers and studies will say: Do not let the UHP WJ nozzle sit on the surface at a single spot; particularly when it is not spinning.
That is reflected as a 0 inch per minute transverse rate. If the focused nozzle is at rest and pointed at one spot, you can get material loss although still at a lower rate than abrasive blasting.