Comparison of HIP in addition to VPS Tungsten Coating Behavior Using Laser Spallation

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Comparison of HIP in addition to VPS Tungsten Coating Behavior Using Laser Spallation

Demas, Cheryl, Founder;Editor;Publisher has reference to this Academic Journal, PHwiki organized this Journal Comparison of HIP in addition to VPS Tungsten Coating Behavior Using Laser Spallation Jaafar El-Awady with significant contributions from H. Kim, J. Quan, S. Sharafat, V. Gupta, G. Romanowski1 in addition to N. Ghoniem Mechanical in addition to Aerospace Engineering Department University of Cali as long as nia Los Angeles 1Oak Ridge National Laboratory 16th High Average Power Laser Workshop Princeton Plasma Physics Laboratory Princeton, NJ Aug. 12 – 13, 2006 Outline The Laser Spallation Technique HIP’d W-F82H measurements Plasma Spray W-F82H measurements Dynamic vs. Static Loading Fracture Mechanics Calculations Conclusion The Laser Spallation Technique Experimental Layout

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HIP’d W-F82H Joint HIP (Hot Isostatic Pressure): W-F82H joint is fabricated with HIP conditions of 1243K, 143MPa in addition to 2 hour holding time. Akiba in addition to Hirose (JAEA) Time HIPPED W-F82H Bond Strength Measurements W Laser Fluence effect on the failure of the bond HIPPED W-F82H Bond Strength Measurements 95% dense W properties W bulk properties 80% dense W properties

VPS-W coated F82H Powder melts in Plasma Flame Molten droplets are accelerated towards substrate Droplets solidify on substrate A new layer of molten droplets solidifies Example of “Popped” VPS-W Coating VPS-W coated F82H Failure Strength VPS-W coated F82H Failure Strength Static test results (Greuner et. al. 2005): Failure occurs in the coating in addition to not at the interface The failure strength is estimated to be 25~30 MPa Failure strength of the coating is: at 1/3 of the thickness

WHY Dynamic vs. Static Loading The material undergoes a ductile-to-brittle transition as the strain rate is increased. The yield stress increases significantly in addition to the work-hardening rate decreased as the strain rate increases. In dynamic loading the fracture toughness is independent of any plastic de as long as mation in addition to geometry effects on the contrary with static loading. Back of the Envelop Calculations of the Required Stress as long as Fracture (Fracture Mechanics) The stress required to propagation a crack in a brittle material can be calculated using an elastic strain energy model: For a 1 mm initial size crack in an 80% dense coating: 80% dense W: (Analytic result) MPa E: modulus of elasticity g = specific surface energy a = one half the length of an internal crack (Experimental result) MPa Conclusions We have successfully tested VPS in addition to HIP’d Tungsten coated ferritic steel samples HIP’d samples fail at the W-F82H interface while VPS samples fail in the W-coating itself Failure strength in HIP’d samples is found to be about twice that in VPS samples For VPS W-F82H the static strength is 25~30 MPa while the dynamic strength is about 450~550 MPa Fracture mechanics gives similar results to our current experimental results We are proposing the use of Fracture toughness instead of tensile properties

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Demas, Cheryl Founder;Editor;Publisher

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