निम्नलिखित में से किस सतह कठोरीकरण (surface hardening) विधि द्वारा अधिकतम सतह कठोरता प्राप्त की जाती है?

The primary objective of performing the annealing process on steel is to:

In a case hardening process, where ammonia gas is introduced to the surface of steel, the process is known as:

Which of the following heat treatment processes is primarily used to relieve internal residual stresses in metallic materials without significantly changing their structure?