0 10 20 30 40 50 60 70 80 90 100110120

Thickness (mils) X 1/1000

Figure 7. Thermal Shock Fatigue Test Life Chart.

Early visual detection is difficult. It is believed that the cracks initiate before visual detection is possible. As a general rule it appears that craze cracking is visually detectable at about 1/3 the number of cycles to coating separation. For example, thin coatings about .040 inch thick which experience coating separation at 3,000-6,000 cycles have recorded visual cracking at 1,000-2,000 cycles. Thick < coatings (over .070 inch thick) which have experienced coating separation at 100-900 cycles have recorded visible craze cracking at 50-300 cycles. Typical coating craze cracks and separation failures are shown in Figure 8.

50 mils Zirconia at 460 Cycles

90 mils Zirconia at 283 Cycles

Figure 8. Typical Thermal Shock Fatigue Rig Coupon Failures.

90 mils Zirconia at 283 Cycles

Figure 8. Typical Thermal Shock Fatigue Rig Coupon Failures.

SCA+CHROME OXIDE

KAMAN SCIENCES THIN (3-5 MILS) DRAIN CAST PROCESS

0 0

Post a comment