Study of the mechanical and metallurgical properties of AMDRY 9954 HVOF coated Ti-6A1-4V alloy
Al-Anazi, Dahham (2007) Study of the mechanical and metallurgical properties of AMDRY 9954 HVOF coated Ti-6A1-4V alloy. PhD thesis, Dublin City University.
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Ti-6A1-4V alloy is commonly used in gas turbines due to its excellent tensile and fatigue strength, corrosion resistance, and high toughness to mass ratio. In the present study, the metallurgical and mechanical properties of High Velocity Oxygen Fuel (HVOF) thermally sprayed AMDRY 9954 (Cobai.Ni32Cr21Al8Yo.5) superalloy powder on Ti-6A1-4V alloy are examined. The mechanical tests include three point bending, tensile, fatigue, indentation, and microhardness tests. The mechanical tests are applied on Ti-6A1-4V specimens (a) asreceived, (b) as-received heat treated, (c) coated then heat treated and (d) coated without heat treatment. Three-point bending tests are carried out to investigate the coating-base material interface properties and the influence of heat treatment on the interface properties. Tensile tests are performed to evaluate the adhesion of the thermally sprayed coating to Ti- 6A1-4V alloy. The fatigue tests are conducted to study the fatigue resistance behavior of the coated substrate martial under fluctuating load. Finite element method (FEM) is introduced to simulate the bending and tensile testing situations and predict the stress distribution in the workpieces. In addition, the microhardness and the indentation tests are carried out to measure the hardness and estimate the plane fracture toughness of the coating, respectively. The metallurgical characterization and surface morphology prior and after mechanical testing are investigated using SEM, optical microscopy, EDS, and XRD. It is found that heat treatment modifies the elastic modulus of the coating; in addition, tensile and fatigue performance of the specimens subjected to the heat treatment is low.
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