| abstract |
The present invention provides a process capable of stabilizing a nickel-base superalloy base material that easily causes a harmful reaction with an aluminum-rich film by carburization. In this process, generally, the surface of the substrate 20 is processed to be substantially free of oxides, the substrate 20 is heated to a carburizing temperature in a non-oxidizing atmosphere, and then the substrate. The surface of the substrate 20 is brought into contact with a carburizing gas mixture containing a diluted low activity hydrocarbon gas while maintaining 20 at the carburizing temperature. While in contact with the carburizing gas at the carburizing temperature, the carbon atoms in the carburizing gas are then dissociated, move onto the surface of the substrate 20, diffuse into the substrate 20, and react with the refractory metal in the substrate 20. Thus, the refractory metal carbide 36 is formed in the carburized region 38 below the surface of the substrate 20. Next, the substrate 20 is cooled in a non-oxidizing atmosphere to finish the formation of carbides. [Selection] Figure 3 |