The main reason for quenching is to enhance hardness and strength. When you heat your material to the critical temperature, partial or complete austenizing takes place.
However, due to rapid cooling, austenite is prevented from transforming into ferrite or pearlite. Instead, it is changed into martensite, resulting in a metal that is very hard and very brittle.
Advantages:
Quenching offers many benefits to metalworkers. These include:
Hardness: Due to martensite formation, quenching makes your metal very hard. Hardness is a non-negotiable factor for components and tools that withstand abrasion, such as bearings and tool sets.
Wear resistance: Quenching enhances the tensile and yield strength of your steel. The rapid cooling locks atoms in a distorted lattice structure. This means dislocations will have a hard time moving around.
Elastic Limit: In manufacturing, quenching is applied to springs to increase their elastic limit.
Drawbacks:
The drawbacks to quench hardening are
Residual stress: Residual stress can be introduced in your metal during quenching. Due to an uneven cooling rate, the surface will cool and contract faster than the interior. Thereby, causing tensile and compressive stresses.
If you don’t manage this risk, your application becomes susceptible to distortion or cracking. Consult your supplier about the best post-quenching techniques for mitigating this issue.
Ductility: Although quench hardening enhances strength and hardness, it causes metal to lose ductility. Since the metal is in a brittle condition, it becomes more prone to stress cracking.
That’s the reason we follow up quenching with tempering. Tempering reduces brittleness without causing strength loss.
