Question

A nickel engine part is coated with SiC to provide corrosion resistance at high temperatures. If no residual stresses are present in the part at 20°C, determine the thermal stresses that develop when the part is heated to 1000°C during use. The elastic modulus of SiC is 60 × 106 psi. The Coefficient of Thermal Expansion for SiC is 4.0 x 10-6 / °C. If the SiC goes past a tensile strength 25,000 psi, the coating will crack. Does the thermal stress go over 25,000 psi?

Answer 1

σ = 235200 psi.

Yes, the thermal stresses go over 25000 psi.

Explanation:

The thermal stresses (σ) can be calculated by:

`\sigma = E \alpha \Delta T`

where α: is the Coefficient of Thermal Expansion, E: is the Young's Modulus and
`\Delta T = T_(f) - T_(o)`,
`T_(f)`: is the final temperature and
`T_(o)`: is the initial temperature.

`\sigma = 4.0 \cdot 10^(-6) \cdot 60 \cdot 10^(6) (1000 - 20 ) = 235200 psi`

So, when the SiC is heated to 1000 °C, it develops 235200 psi of thermal stresses.

The answer to the question is yes, the thermal stresses go over 25000 psi.

I hope it helps you!