AWS Welding Metallurgy & Heat Treatment 3

Question 1

What welding metallurgy phenomenon causes the HAZ of certain stainless steels to become susceptible to intergranular corrosion?

Accepted Answer

Sensitization from chromium carbide precipitation

Answer

Sensitization occurs when chromium carbides precipitate at grain boundaries in the 425–870°C range, depleting adjacent areas of chromium and reducing corrosion resistance.

Question 2

The liquidus temperature in a binary alloy phase diagram represents:

Accepted Answer

Temperature above which the alloy is completely liquid

Answer

The liquidus is the temperature above which the alloy exists entirely as liquid; below this line, solidification begins.

Question 3

In welding metallurgy, 'dilution' refers to:

Accepted Answer

Reduction in weld metal properties due to base metal mixing

Answer

Dilution is the proportion of base metal melted into the weld pool, which changes the weld metal chemistry and can affect mechanical properties and corrosion resistance.

Question 4

Which intermetallic phase in stainless steel welds severely embrittles the material at elevated service temperatures?

Accepted Answer

Sigma phase

Answer

Sigma phase, an iron-chromium intermetallic compound, forms between 600–900°C and causes severe embrittlement with near-zero impact toughness.

Question 5

The Schaeffler diagram is used in welding to predict the microstructure of:

Accepted Answer

Stainless steel weld metal based on Cr and Ni equivalents

Answer

The Schaeffler (and WRC) diagram plots chromium equivalent vs. nickel equivalent to predict the ferrite, austenite, and martensite content of stainless steel weld deposits.

AWS Practice Test

AWS Practice Test

AWS Welding Metallurgy & Heat Treatment 3