Study On 17-7PH Stainless Steel Pump Shaft Bending Failure And Microstructure

Used for vertical multistage anti-corrosive pump shaft bending in the process of commissioning and radial runout more than technical requirements. The hardness measurement of failed pump shaft is below the lower limit of the technical requirements. Paper to failure of pump shaft as the research object, through optical microscope (OPM) and scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis test means such as the failed pump shaft materials (17-7 PH precipitation hardening stainless steel) organization structure characteristics, and the determination of the failed pump shaft material hardness, tensile properties and mechanical properties. Analysis results show that the hardness and tensile strength and low pump shaft materials related to abnormal tissue. Simulated heat treatment test paper, and compared with standard heat treatment process (limitation of solid solution+ adjustment+aging) gained by the pump shaft under the organization of material and mechanical properties of comparison, determine the cause of the pump shaft appear abnormal tissue, is the cause of failed pump shaft. Paper main conclusions are as follows:1. The failure pump shaft matrix hardness of HRC 22-26, is far lower than the technical requirements (HRC 30～35). Pump shaft bending failure and excessive radial runout and pump shaft hardness is low.2. The failed pump shaft is mainly composed of lath martensite, delta ferrite and reverse change o.f austenite, the austenite content up to 32.6%. Lath martensite was observed precipitation hardening phase, or other presettling organization.3. The standard heat treatment process of pump shaft by material residual austenite content is 24.6%, the strip in the martensite age hardening organization amplitude modulation. The pump shaft material substrate average 31.3 meet the technical requirements, and hardness relaed to failed pump shaft material, the tensile strength increased significantly.4. The change of the solution treatment and adjustment process has nothing to do with the emergence of the pump shaft material abnormal tissue, so as the large number of reverse austenite.5. The temperature is higher than the standard aging treatment, reverse austenite content will increase with the increase of aging temperature, and accompanied by age group. The material hardness of pump shaft also reduce with the increase of aging temperature.6. Heat treatment of the failed pump shaft material is lead to the abnormal structure, low hardness and strength of the main reasons.7. The failed pump shaft nature is a lack of strength, stiffness, low strength and rigidity of pump shaft materials cause the pump shaft bending failure, radial runout.