Method for manufacturing heat resisting member applicable to an exhaust gas guide assembly with improved heat resistance for VGS turbocharger

Abstract

An exhaust gas guide assembly with an improved high-temperature wear resistance, oxidation resistance, high-temperature strength or the like for a VGS turbocharger is provided. According to the invention, the exhaust gas guide assembly for a VGS turbocharger includes adjustable blades, a turbine frame and an adjusting mechanism is characterized in that a heat resisting member constitutes the exhaust gas guide assembly to remarkably enhance high-temperature durability or the like of the exhaust gas guide assembly.

1 - 27 . (canceled) 
   
   
       28 . A method of manufacturing a heat resisting member applicable to an exhaust gas guide assembly for a VGS turbocharger, the exhaust gas guide assembly including adjustable blades for suitably controlling a flow rate of exhaust gas discharged from an engine to rotate an exhaust turbine wheel, a turbine frame rotatably supporting the adjustable blades outside of an outer periphery of the turbine wheel, and an adjusting mechanism for suitably rotating the adjustable blades to control the flow rate of the exhaust gas such that a flow of the exhaust gas at a low flow rate is throttled by the adjustable blades to increase a velocity of the exhaust gas so that a high output power is obtained at low rotational speeds, said method comprising:
 subjecting a material of a heat resisting member of an exhaust gas guide assembly to ion carburizing, the material being selected from a group consisting of high-alloy austenitic heat resisting stainless steel, iron based superalloy, and nickel based superalloy; and   subsequently, carrying out a TD salt bath treatment.   
   
   
       29 . The method of  claim 28 , wherein, if the high-alloy austenitic heat resisting stainless steel is selected as the material, one or more of Ti, Nb, B, Hf and Zr are contained in the material. 
   
   
       30 . The method of  claim 28 , wherein, if the iron based superalloy is selected as the material, one or more of Ti, Nb, B, Hf and Zr are contained in the material. 
   
   
       31 . The method of  claim 28 , wherein, if a rolled product of the high-alloy austenitic heat resisting stainless steel or the iron based superalloy is selected as the material, the material is subjected to hot-rolling with a large rolling reduction in the ferrite region to become fine-grained. 
   
   
       32 . The method of  claim 28 , wherein, if the nickel based superalloy is selected as the material, internal strains are accumulated under stress, to thereby precipitate a fine-grained γ′ phase while the internal strains serve as nuclei.