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4169 high temperature alloy is added Nb precipitation strengthening nickel - chromium - iron-based alloys. The alloy is below 650 ℃ has a higher yield strength, tensile strength and good anti-fatigue, anti-oxidation, anti-radiation, corrosion resistance, and has good processing properties, the welding performance, can be made of the disk, the ring, the blade shaft, fasteners and elastic components, sheet metal structural components, casing and other components in aerospace vehicles, long-term use. 4169 high temperature alloy coating prepared by laser cladding technology exists segregation of niobium, niobium segregation will produce harmful Laves phase, strongly influenced by the microstructure and properties of the alloy, and to limit the application of laser cladding 4169 alloy remanufacturing process . This paper studies the impact of laser power and substrate temperature on the behavior of the 4169 alloy coating niobium segregation, and niobium segregation on the microstructure and mechanical properties of the coating. The microstructure observation that 4169 high temperature alloy solidification process of laser cladding showing typical epitaxial growth characteristics. Alloy coating different growth direction slender columnar dendrites composed of high gradient laser rapid melting, solidification of the high-speed characteristics, resulting organized crime, even. Differential thermal analysis and phase analysis results show that the 4169 high temperature alloy solidification process is divided into three steps: The first step is to generate the austenite phase L → γ; second step, the eutectic reaction L → (γ NbC); step, eutectic reaction L → (γ Laves). The laser power on the tissue affected the results showed that the cracks present in the the 4169 alloy coating obtained in the higher laser power of 5KW, and the crack does not exist in the alloy coating is obtained under the lower laser power of 1.5KW; 1.5KW cladding alloy coating obtained in the laser power of the cooling rate is large, the small degree of segregation of niobium less the harmful phase Laves phase coating. The results showed that the liquid nitrogen cooling the substrate impact on the organization, cooling the substrate with liquid nitrogen can increase the cooling speed of the coating and the substrate at room temperature when the coating a cooling rate of 941 ± 122 ° C / s, the coating liquid nitrogen cooling of the substrate when the cooling rate is 3124 ± 517 ℃ / s; cooled by liquid nitrogen can suppress the 4169 alloy coated niobium segregation, the organization of the coating harmful finer phase Laves phase, while the Laves phase volume decreased. The heat treatment results show that the heat treatment can significantly increase the hardness of the 4169 alloy coating, prepared under the low power of the coating after heat treatment higher hardness (5KW: 400 HV, 1.5KW: 460HV), the liquid nitrogen cooling conditions of the substrate under the coating prepared layer higher hardness after heat treatment (substrate at room temperature: 460HV, liquid nitrogen cooling: 482HV).
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