Dissertation > Excellent graduate degree dissertation topics show

Study on the Formation of Residual Stress in Thernal Spray Coatings and Its Controlling Factors

Author: ZhaoJiaoYu
Tutor: ZhangZhongLi
School: Shenyang University of Technology
Course: Materials Processing Engineering
Keywords: Thermal Spraying Residual Stress 4Cr13 65Mn Young’s Modulus
CLC: TG174.44
Type: Master's thesis
Year: 2009
Downloads: 268
Quote: 2
Read: Download Dissertation

Abstract


Due to the nature of the thermal spray process, residual stress formed in thick coating is a clarification of objective. Residual stress affects the microstructure and micro-hardness of the coating, result in micro-cracks in the coating and reduce the strength between coating and the substrate. In some cases it could lead to cracks, even pull out, causing the failure of work piece.The residual stress of coatings is not only related to the kind of materials, but also affected by the spraying method, spraying parameters and the size of work piece. The residual stress-state that evolves in a deposit is largely dependent on the thermal conditions under to the system has been subjected, and is a combination of quenching stresses which arise during deposition, and cooling stresses post-deposition. Therefore, study residual stress in theory and experiment has great value for get high-quality thermal spray coating and re-manufacturing engineering coating technology.The work of this paper analyzed the formation mechanism of thermal spray coating stress, elaborated the main residual stress test method which in the process the residual stress produces, introduced some test method principle and evaluated respective superiority and the limitation. And, it designed a special experimental device, used curvature to measure the residual stress and studied the effects of the change of the parameters of spraying on the residual stress in the coatings. The work also analyzed the coating microstructure by SEM and studied the transformation process of residual stress changes in the mechanism. By means of electrical measurement and curvature method, Young’s modulus of two coatings were measured, providing a research method and data reference for the coating stress study.The results show that Young’s modulus of 4Cr13 coatings is 53GPa. The Young’s modulus of 65Mn coatings is 105 GPa. Young’s modulus of the coating is less than the Young’s modulus of original material. The residual stresses of the coatings sprayed at different temperatures are different when cooled to room temperature. For the coating with the transformation, it exist a critical temperature which leads to a zero coating’s residual stress. Sprayed at higher temperatures than the critical, the coating was at the state of tensile stress, while sprayed at lower temperatures than the critical; the coating was at the state of compressive stress. The critical point of 4Cr13 coating is about 260℃and that of 65Mn coating is about 300℃. With the increase of spraying current, the tensile stress of coating increases. Similar to the influence of spraying current, the increase of spraying voltage also have the tensile stress of coating increased.

Related Dissertations

  1. Study of Mechanism Using Two-Direction Pre-Stress to Control Welding Distortion and Hot Cracking,TG404
  2. Welding residual stress on LNG ship tank bulkhead fatigue life,U671.83
  3. Butt welding of hull shapes Numerical Simulation and Optimization,U671.8
  4. Min Pu Bridge Construction Technology of Steel,U445.4
  5. Theoretical Study on Test of Young’s Modulus of Elasticity and Poisson’s Ratio for Films,TB43
  6. The Influence and Mechanism of Residual Stress of High-temperature Welding for 16MnR Welding,TG404
  7. Evolution of Shear Band, Free Volume and Hardness of as Rolled Zr-based Bulk Metallic Glasses,TG339
  8. Effect of the Rubbing and Wearing Behavior of Steel Rail by Ultrasonic Peening,TG115.58
  9. The Research on Surface-strengthening Technology Via Warm Surface-rolling,TG376
  10. Electron beam welded joints under fatigue properties and residual stress of,TG405
  11. Laser Cladding Ti / HA composite process heat - mechanical coupling analysis and numerical simulation,TG174.44
  12. Simulation and Experiment Research of Fatigue Life Improvement of Titanium Alloy by Laser Shock Processing,TG665
  13. Finite Element Simulation and Theoretical Analysis of High Speed Cutting of Advanced Metallic Materials,TG506.1
  14. Fea Analysis of Residual Stress for Heat Treatment of Oil Casing,TG156.3
  15. Study on Preparation and Tribological Properties of Fe-based Amorphous Coating Deposited by Arc Spraying,TG174.44
  16. Welding Stress and Deformation Analysis of Leg Racks of Marine Petroleum Platform Using Thermal Elastic-Plastic Finite Element Method,TG404
  17. Analysis of Residual Stress of Thermal Barrier Coatings System with Curved Substrate by Finite Element Method,TG174.4
  18. Analysis of Three-dimensional Residual Stress Fields and Interfacial Buckling Delamination Failure of Thermal Barrier Coating with Cylindrical Geometry,TG174.4
  19. Research on the Physic and Mechanic Properties in the Surface of Closed Extruding Fine-blanking Works,TG386
  20. Dynamic Visualization Experimental Study of Internal Stress on the Optical Products,TQ320.662
  21. Research on Corrosion Behaviors of Thermal Sprayed WC-Co/Cr and Al2O3/TiO2 Coatings in Saline,TG174.442

CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > Corrosion control and protection > Metal surface protection technology > Metal complex layer of protection
© 2012 www.DissertationTopic.Net  Mobile