激光沉积修复gh4169/Gh738合金时效热处理组织与摩擦磨损性能
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Cited by 2 publications
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母材显微组织对激光沉积修复k4169合金液化裂纹敏感性的影响
Objective K4169 hightemperature alloys exhibit high strength, plasticity, and heatcorrosion resistance in the middle and lowtemperature ranges and are particularly suitable for manufacturing aircraft engines. The ascast state of the K4169 alloy is prone to severe elemental segregation, resulting in deteriorated welding performance. The presence of liquation cracks in the heataffected zone significantly reduces the safety and operational reliability of the product. To enhance the quality of repairs, laser pretreatment is employed to adjust the composition, structure, and phase distribution of the base material while reducing its strength and hardness to improve the liquation crack sensitivity of the matrix material. However, a systematic study of the prelaser treatment process for K4169 nickelbased hightemperature alloys has not been carried out. In particular, the influence of the base material' s structure on crack initiation mechanisms is not well understood. Therefore, this study emphasizes the necessity of employing pretreatment processes to regulate the K4169 alloy base material before repair, and conducts indepth research on the sensitivity and mechanisms of liquation cracks in the repaired specimen's heataffected zone. The results of this study have significant implications for the highquality repair of nickelbased hightemperaturealloy components in aerospace.Methods This study employed a homogenization+solution+aging treatment and homogenization+hot isostatic pressing+ solution+aging treatment on a K4169 alloy substrate prior to repair, followed by repair experiments using the laser deposition process with synchronized powder feeding for different substrate microstructures. The repaired specimens subjected to the homogenization+ solution+aging treatment were denoted LDR, whereas those subjected to the homogenization+hot isostatic pressing+solution+ aging treatment were denoted LDR -K9. The process parameters included a laser power of 1600 W, scanning speed of 8 mm/s, scanning speed of 1 rad/min, overlap rate of 40%, and laser diameter of 3 mm. Subsequently, the crosssections of the heattreated substrate and repaired specimens were ground and polished, followed by corrosion using a solution of hydrochloric acid, nitric acid, and hydrofluoric acid (80 mL HCl+7 mL HNO 3 +13 mL HF). The microstructures of the substrate specimen crosssections and the distribution and characteristics of cracks in the repaired specimens were observed using an OLYMPUS GX 51 optical microscope (OM) and a ZEISS Sigma300 scanning electron microscope (SEM). Energydispersive spectroscopy (EDS) was employed to characterize the distribution of elements in the substrate region. Phase analysis was performed using a Bruker d2 -phaser Xray diffractometer (XRD). Microhardness measurements of the repair, heataffected, and substrate zones were conducted using an HVS -1000Z Vickers hardness tester under a 1.96 N load for 15 s. Tensile tests were performed using an INSTRON5982 universal testing machine at a strain rate of 0. 5 mm/min. Results an...
母材显微组织对激光沉积修复k4169合金液化裂纹敏感性的影响
Objective K4169 hightemperature alloys exhibit high strength, plasticity, and heatcorrosion resistance in the middle and lowtemperature ranges and are particularly suitable for manufacturing aircraft engines. The ascast state of the K4169 alloy is prone to severe elemental segregation, resulting in deteriorated welding performance. The presence of liquation cracks in the heataffected zone significantly reduces the safety and operational reliability of the product. To enhance the quality of repairs, laser pretreatment is employed to adjust the composition, structure, and phase distribution of the base material while reducing its strength and hardness to improve the liquation crack sensitivity of the matrix material. However, a systematic study of the prelaser treatment process for K4169 nickelbased hightemperature alloys has not been carried out. In particular, the influence of the base material' s structure on crack initiation mechanisms is not well understood. Therefore, this study emphasizes the necessity of employing pretreatment processes to regulate the K4169 alloy base material before repair, and conducts indepth research on the sensitivity and mechanisms of liquation cracks in the repaired specimen's heataffected zone. The results of this study have significant implications for the highquality repair of nickelbased hightemperaturealloy components in aerospace.Methods This study employed a homogenization+solution+aging treatment and homogenization+hot isostatic pressing+ solution+aging treatment on a K4169 alloy substrate prior to repair, followed by repair experiments using the laser deposition process with synchronized powder feeding for different substrate microstructures. The repaired specimens subjected to the homogenization+ solution+aging treatment were denoted LDR, whereas those subjected to the homogenization+hot isostatic pressing+solution+ aging treatment were denoted LDR -K9. The process parameters included a laser power of 1600 W, scanning speed of 8 mm/s, scanning speed of 1 rad/min, overlap rate of 40%, and laser diameter of 3 mm. Subsequently, the crosssections of the heattreated substrate and repaired specimens were ground and polished, followed by corrosion using a solution of hydrochloric acid, nitric acid, and hydrofluoric acid (80 mL HCl+7 mL HNO 3 +13 mL HF). The microstructures of the substrate specimen crosssections and the distribution and characteristics of cracks in the repaired specimens were observed using an OLYMPUS GX 51 optical microscope (OM) and a ZEISS Sigma300 scanning electron microscope (SEM). Energydispersive spectroscopy (EDS) was employed to characterize the distribution of elements in the substrate region. Phase analysis was performed using a Bruker d2 -phaser Xray diffractometer (XRD). Microhardness measurements of the repair, heataffected, and substrate zones were conducted using an HVS -1000Z Vickers hardness tester under a 1.96 N load for 15 s. Tensile tests were performed using an INSTRON5982 universal testing machine at a strain rate of 0. 5 mm/min. Results an...
Dd6镍基单晶高温合金激光重熔区杂晶的形成机制研究
Objective Nickelbased singlecrystal superalloys are widely used in the manufacture of singlecrystal turbine blades in the combustion chambers of aircraft engines owing to their excellent hightemperature mechanical properties. However, these components often suffer from severe damage, such as edge erosion, cracking, and pitting, owing to the harsh operating conditions, including high temperatures and pressures, requiring repairs to extend their service life. Laser additive manufacturing technology has garnered significant attention for repairing nickelbased singlecrystal superalloys owing to its unique advantages, including controllable heat input, the ability to fabricate complex structures, and reparability. However, the appearance of grain defects during the repair process may lead to serious failure phenomena, such as crack propagation and component fracture, during component operation, thereby posing potential risks to the safety and reliability of aircraft engines. Therefore, this study selected a DD6 secondgeneration nickel based singlecrystal superalloy as the substrate material and used lasers with powers of 1200 and 1500 W to remelt the substrate, revealing the mechanisms of stray grain formation at the fusion line, top of the molten pool, and at the intersection of the dendrites, thereby providing a theoretical basis and technical support for the laser additive repair of nickelbased singlecrystal superalloys.Methods This study employed a DD6 nickelbased singlecrystal hightemperature alloy prepared via directional solidification as an experimental substrate material. Subsequently, a laser cladding additive manufacturing device equipped with a 2 kW German Rofin fibercoupled semiconductor laser was utilized. The process parameters included laser powers of 1200 and 1500 W, a scanning rate of 3 mm/s, and a spot diameter of 4 mm for the singletrack remelting experiments on the substrate (001) crystal surface. To prevent sample oxidation during remelting, argon gas was used as a protective gas at a flow rate of 10 L/min. The dendritic morphologies of the substrate and remelted region were observed using an OLYMPUS DSX510 optical microscope. Simultaneously, scanning electron microscopy and Xray energydispersive spectroscopy were employed for detailed analysis of the molten pool morphology and elemental distribution. Electron backscatter diffraction (EBSD) analysis was performed to further investigate the crystallographic properties of the specimens. The sample tilt angle was set to 70°, with a scan step size of 3 μm, using nickel as the calibration phase.HKL Channel 5 postprocessing software was employed for texture and orientation deviation analysis of the samples. Results and DiscussionsThe results show that, after laser remelting, the molten pool could be divided into four regions ([001],[100], [010], and [01 ˉ0]) based on the growth direction of the grains (Fig. 3), and the primary dendrite spacing increased with increasing laser power. From the crystallographic texture characteristics of the molten pool (F...
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