Marine Applications of Deep Cryogenic Treatment
Racing puts unbelievable stresses on mechanical components. A quick look at this boat propeller will attest to that. It is rated at 1500 horsepower. The crack is huge, and luckily it stopped short of breaking the tip off.
This prop was on a racing boat owned by four-time offshore champion Rick Bowling, who runs twin Mercury Marine motors rated at 1350HP. It is made of a magnetic stainless steel described by Mercury Racing as a proprietary alloy. The prop costs over $5000.
Close up of the Crack. Note Beach marks indicating the crack is a fatigue failure.
Cracked propeller off of the racing boat "Gone Again"
The crack shows “beach marks” (Indicated by the red arrow), which distinctly identifies it as a fatigue related crack. Most likely, the prop received some damage from striking debris in the water. That damage caused a stress concentration. Other blades show damage nicks at about the same area of the blade. These are indicated by black marks on the blades. There may also have been a discontinuity or an inclusion in the casting, which we are looking into.
The failure of the prop could have been worse. Had the blade separated on the up stroke it could have been thrown a heavy piece of metal at a considerable speed for a considerable distance. It would have made the propeller extremely out of balance which could have had destructive consequences to the drive system on the boat.
Cryogenic boat propeller treatment of the replacement through a process known as Deep Cryogenic Treatment (DCT) has dramatically improved the durability of the part greatly increasing its length of service life. The treated prop has three times the running hours on it of all previous props used. As of January 6, 2016, the treated replacement prop is still running strong. We will publish the total hours after the prop is out of service.
Other Marine Uses
Final drive gears and shafts benefit greatly from DCT. Propulsion shafts do also. Of course engine parts and transmission gears all exhibit benefits.