AVOIDANCE OF HYDROGEN EMBRITTLEMENT OF STEEL FASTENERS AND OTHER HARDENED OR SPRING STEEL PARTS FROM SURFACE COATING PROCESSES
|Publication Date:||1 February 2019|
This standard outlines the conditions that enhance the risk of hydrogen embrittlement of steel and define the relief procedures required to minimize the risk of hydrogen embrittlement. It is intended to control the process.
Hydrogen embrittlement of steel, which can cause brittle fractures under stress, occurs as a result of the absorption of hydrogen during cleaning, phosphate coating and plating processes. The susceptibility to hydrogen embrittlement increases with increasing stress (internal or externally applied stress) and increasing material strength (hardness).
Residual phosphate on the steel surface prior to heat treating can lead the formation of delta ferrite microstructure - a white phosphorus enriched layer. This brittle surface layer may lower the fatigue life of the component.
Exposing parts to temperatures near the melting point of the metal causes the diffusion of the metal into the substrate resulting in a loss of ductility commonly referred to as liquid metal embrittlement.
Hardness values in this specification are in Rockwell C (HRc) hardness scale. SAE J417 or ISO 18265 shall be referred to for conversion to other scales.
Deviations or non-compliance with any part of this standard shall be agreed upon by the OEM.
Oven controls and verification shall be conducted in accordance with CQI-11.