GCr15钢激光表面熔凝组织

MICROSTRUCTURE OF LASERGLAZED STEEL GCrl5

本文采用1kW直流式CO_2激光器研究了激光表面快速熔凝处理对GCr15钢显微组织形貌的影响。结果表明,试样表面经涂复石墨粉混合物黑化处理后,在高能激光束作用下,GCr15钢表面熔化区迅速增碳,并向邻近过热区扩散。其中,熔化区是由细小的初晶奥氏体和共晶莱氏体(奥氏体+碳化物)组成具有一定方向性的亚共晶组织,而过热区则主要为残余奥氏体的粗大晶粒组织。利用高温金相显微镜拍摄了奥氏体在应力作用下的浮凸过程,并发现在其局部区域形成的典型蝶状马氏体组织。分析表明,该特殊组织的出现与碳原子在奥氏体中的不均匀分布及其所受到的应力促发作用有关。

The influence of rapid surface melting treatment by laser was studied by using 1 KW CO_2 laser upon microstructure in steel GCr15. It was shown that under the irradiation of laser beam on the coated specimen surface with a mixture of graphite powder and some organic materials, the carbon content increases sharply in the melted zone, resulting in a partly oriented hypoeutectic structure consisted of tiny primary austenite and ledeburite, However, in the adjacent heat affected zone a diffusion layer appears, and the microstructure is mainly residual coarse austenite grains. In situ observation of relief-formation process in austenite grains under residual stress was done by high-temperature microscope. It was found that martensite of butterfly type was locally formed. This is possibly associated with the heterogeneous distribution of carbon and the stress-induced effect in austenite.