Question

Which of the following is not an effect of adding boron and silicon to superalloys?

(a) Improves adhesion

(b) Maintains oxide layer

(c) Increases spalling

(d) Reduces spalling

I have been asked this question during an online exam.

My enquiry is from Refractory Materials, Superalloys topic in chapter Refractories & Dielectric Materials of Engineering Material & Metallurgy

Answer 1

Right option is (c) Increases spalling

Easiest explanation: Since superalloys are operated at high temperatures, they are susceptible to degradation of quality. Addition of elements like boron, silicon, and yttrium improves adhesion, reduces spalling, and maintains the protective oxide layer. This is a minor form of degradation which can be corrected by coatings.