E. By pressure-injection of a hot mold material 9. What is a nitriding of silico

Question

E. By pressure-injection of a hot mold material 9. What is a nitriding of silicon? A. Quenching by immersion in liquid nitrogen B. Reaction with nitrogen-bearing compounds C. Elimination of stress concentrations D. Elimination of cracks E. Surface abrasion 3. What is one advantage of investment casting (IC) for forming turbine blades? A. IC requires hand-sculpted molds. B. IC molds can be reused many times. C. IC is faster than injection molding. D. IC is useful for hard-to-machine parts. E.) IC produces fine grains to promote diffusion. 10. What is the limit of blade cooling? A. Atmospheric nitrogen causes nitriding. B. Blade cooling leads to thermal fatigue. C. )Injection of cold air can reduce the engine's 4. How is directional solidification carried out? A. The mold is rotated in a centrifuge. B. Liquid nitrogen is used to quench the part. thermal efficiency D. Elimination of Freon has made refrigeration units too large and heavy. E. Injected air causes high-temperature oxida- C.) The mold is slowly withdrawn from the fur- nace. tion of the nickel super-alloy D. Air circulates through internal cooling chan- 11. What is the purpose of stable precipitates such nels. E. Air is injected through film-cooling ports. 5. What is an advantage of directional solidifica- as NisAl, NisTi, MoC and TaC in a nickel-based super-alloy intended for high-temperature use? A. To increase the elastic modulus tion (DS)? A. DS is cheaper than other methods. B. DS produces long grains aligned with stressD. To blunt crack tips To hinder dislocation glide C. To increase the density to minimize creep. E. To increase density exceptionally tine gras to 12. What is the purpose of subs crease diffusion rates. D. DS eliminates precipitates. E. DS eliminates substitutional solutions. in a nickel-based super-alloy intended for high temperature use? A. To increase the elastic modulus

Explanation / Answer

5 D true : Directional solidification is basically used for impurity removal, so is used for elimination of precipitate

9 B : Silicon nitride is very stable compound , it can be form by heating silicon powder with nitrogen bearing compond ( NH3, N2) to high temperature. with this reaction the compound form is vary stable.

9 B true

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