Delamination initiation life and growth behaviour of ceramic coated steels quenched after coating process under rolling contact loading condition.

In order to investigate the effects of a new surface modification method, 'the substrate quenching after coating' on the rolling contact fatigue strength, TiN coated steel specimens and CrAlN coated steel specimens were processed by this method and the thrust type rolling contact fatigue tests were carried out for these specimens. In the process of the substrate quenching after coating, two types of quenching methods, furnace quenching and laser quenching, were used. For the furnace quenched specimens, the delamination initiation life of CrAlN coated specimen was longer than that of TiN coated specimen. This reason could be explained by the difference of the oxidisation of CrAlN and TiN in their furnace quenching process. For CrAlN coated specimens, the delamination initiation life of the laser quenched specimens was longer than that of the furnace quenched specimens. After the initiation, the delamination of the furnace quenched specimen grew much faster than that of laser quenched specimen. These reasons could be explained by the difference of the process time of the furnace quenching and the laser quenching. The process time, in which the ceramic coating of the specimen was exposed to an elevated temperature, of the furnace quenching was much longer than that of laser quenching. It is considered that substrate laser quenching after coating could be an effective way to improve the delamination initiation life and to reduce the delamination growth rate under rolling contact fatigue. [ABSTRACT FROM AUTHOR]