High durability has been required for electrical components of automobiles, especially rolling bearings used in alternators. It is due to the reduction in size and weight of automotive parts, which are exposed to a higher surface pressure and higher temperature load on electrical components than ever before. Rolling bearings in such an environment often have a markedly shortened life with flaking. It is considered that the cause of flaking is the structural change of steel (hydrogen embrittlement) induced by the penetration of hydrogen into the steel material of the rolling bearing. However, this theory is based on confirming the short life of rolling bearings that have absorbed hydrogen by various methods, and there have been few examples of directly observation that hydrogen penetrates into rolling bearings during lubrication. Therefore, in order to describe the features of time-of-flight secondary ion mass spectrometry (ToF-SIMS) with extremely high performance of surface analyses, and introduce in detail of a case that ToF-SIMS measurements succeeded in directly observing hydrogen that has penetrated into the bearing steel.
