Very few references have been made to the failure of friction welds in steels. However hydrogen cracks and sulphide inclusions were identified in an inertia friction welded joint between low alloy steel (AISI 4137-H) and API 5A gradeE pipe. Sulphide stress corrosion cracking was identified as the weld failure mechanism.
Another example of hydrogen affecting friction weld integrity concerned the joining of a steel casting and steel forged bar, where the hydrogen is known to have originated in the steel casting. Once the casting had been subjected to a hydrogen removal heat treatment no further incidences of failure were recorded.
It should be noted that there is no molten weld pool associated with friction welding and therefore a much reduced opportunity for absorption of hydrogen. However, it is recommended that faying surfaces should be free from grease, oxides and other contaminants.
For further information see Joining Technologies.