In order to investigate the effects of new surface modification method "Laser quenching after coating" on the rolling contact fatigue strength of ceramic coated steels, CrAIN coated steel specimens and TiAIN 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 laser quenching after coating, laser irradiation was carried out under various laser power conditions. The delamination initiation life of CrAIN coated specimen increased with the heat input, however the excessive heat input decreased the delamination initiation life. The adhesive strength of CrAIN coated specimen showed similar variation for the increase of the heat input, and a good correlation was recognized between the delamination initiation life and the adhesive strength. It was considered that the delamination initiation life of CrAIN coated specimen was strongly affected by the adhesive strength. For TiAIN coated specimen, the delamination initiation life once increased and then decreased with increasing the heat input, although the adhesive strength increased monotonously. The hardness of TiAlN film decreased from the heat input at which the delamination initiation life began to decrease. By laser irradiation, the film hardness of TiAIN decreased more easily than that of CrAIN, because the oxidation temperature of TiAIN was lower than CrAIN. The decrease of the delamination initiation life of TiAIN coated specimen laser-irradiated under the high heat input condition could be explained by the decrease of the film hardness. The delamination initiation life of TiAIN coated specimen was strongly affected by the decrease of the film hardness caused by laser irradiation.
