Examination of Cadmium-Plated Aircraft Fasteners for Hydrogen Embrittlement

Book excerpt: The Army Technology Materials Laboratory (AMTL) participated in a possible hydrogen embrittlement (HE) problem involving a variety of cadmium-plated AISI4340 steel fasteners used in OH-58 and CH-47 helicopters. These fasteners were being reworked at an Army depot where cadmium plating was carried out according to Federal Specification QQ-P-416C. A three-month period was considered suspect for cadmium-plated items processed at the depot, and AMTL was supplied with a number of fasteners (bolts), both new and reworked at the depot during the suspect period, for evaluation. These fasteners were sustained load tested for evidence of HE. All of the bolts provided by the depot survived at least 200 h of testing without cracking or fracture. Several of the bolts which were plated during the suspect period and which had passed HE relief tests were deliberately fractured for examination of failure mode. The fracture topography showed no evidence of HE effects. Hardness and cadmium plating thickness measurements were consistent with specification requirements.