It is reported by TWI (The Welding Institute) that Nickel alloys can suffer with porosity if Nitrogen is present in the purge environment with a concentration of as little as 0.025% (250 ppm).
As a result, it is necessary to back purge Nickel alloy joints to better than 80 ppm Oxygen.
For this purpose, it would be wise for all operators to specify that a “Weld Purge Monitor” should be used to check the purge gas quality prior to welding.
Standard “Wet Cell” Weld Purge Monitors are accurate to 100 ppm, however there are now low cost, entry level, Weld Purge Monitors available with zirconia sensors that are very accurate to 10 ppm.
