Strengthening of Ceramic Coated Steel by Laser Quenching

Abstract

In order to investigate the effectiveness of laser quenching for ceramic coated steels, 2 kinds of ceramic coated specimens of CrAlN and TiAlN were prepared, and the laser quenching experiments under various irradiation conditions were carried out. The influence of laser irradiation on the substrate hardness, film hardness and adhesive strength were investigated. Because of the high heat absorption of CrAlN and TiAlN films when compared to TiN, it was possible to quench the substrate effectively without any absorbent material for these specimens, although an absorbent was required for TiN coated specimen. The quenched area on the cross section of the substrate of CrAlN coated specimen was larger than that of TiAlN coated specimen. The difference of the quenched area could be explained by the difference of the heat absorption of these films. It was also possible to improve the adhesive strength of these films by laser irradiation. Although the film hardness decreased considerably by furnace quenching for ceramic coated steels, film hardness did not decrease by laser irradiation. It was concluded that the improvement of the adhesive strength and substrate hardness without the decrease of film hardness was achieved by laser quenching for CrAlN and TiAlN coated specimens.

Quenching of Ceramic Coated Steels by Scanning Laser

“…It was found that laser quenching after coating allows for adequate steel hardness control regardless of the environment temperature during the process without high thermal distortion. Additionally, from a study conducted on CrAlN coated steel and TiAlN coated steel, we were able to conclude that adhesive strength of these ceramic-coated steels improved significantly through laser quenching after coating [2]. These results suggest that this method can be applied as an effective way to improve the performance of ceramic-coated steels.…”

“…When the temperature during deposition is higher than the tempering temperature for a given type of substrate steel, the substrate hardness will typically decrease during the coating process. To solve this problem, "laser quenching after coating" was proposed [1,2]. It was found that laser quenching after coating allows for adequate steel hardness control regardless of the environment temperature during the process without high thermal distortion.…”

“…These results suggest that this method can be applied as an effective way to improve the performance of ceramic-coated steels. In our previous study [1,2], linear scanning laser heat treatment was carried out by using a Nd-YAG laser with a Gaussian type intensity distribution. Using this type sets limitations on the maximum width of the quenching region and may result in non-uniform hardness distribution in the laser irradiated region.…”

Influence of Laser Heat Treatment on Fracture Strength of Ceramic Thin Film

“…From these results, it was concluded that the application of laser heat treatment for the process of substrate quenching after coating can effectively prevent the fracture strength loss of ceramic thin films. Moreover, considering the results obtained in our previous research [6], it is thought that an enhancement of the adhesive strength as well as the substrate hardness with no detrimental effect on the film hardness or it`s fracture strength is possible if laser quenching is applied.…”

“…In addition to the mentioned furnace quenching method, laser quenching was proposed to address this issue due to the localized heat input and consequently very low thermal distortion. A fundamental study on laser quenching using ceramic coated steels (CrAlN and TiAlN) was carried out and it was found that laser quenching after coating improved the adhesive strength and substrate hardness without affecting the film hardness for both types of ceramic coated steels [6]. The investigation of the laser irradiation effect on the fracture strength of ceramic thin film was the next step of the present research.…”