The decomposition of austenite, during controlled cooling or quenching, produces a wide variety of microstructures in response to such factors as steel composition, temperature of transformation, and cooling rate. This chapter provides a detailed discussion on the isothermal transformation and continuous cooling transformation diagrams that characterize the conditions that produce the various microstructures. It discusses the mechanism and process variables of quenching of steel, explaining the factors involved in the mechanism of quenching. In addition, the chapter provides information on the causes and characteristics of residual stresses, distortion, and quench cracking of steel.

This chapter discusses the quenching process and its adaptation to induction heat treating. It describes the three stages of quenching, the cooling characteristics of various types of quenchants, and the details of nearly a dozen compatible quenching methods. It also explains how to verify whether a quenchant can cool a workpiece fast enough to achieve martensitic transformation without cracking or distortion.

Quenching is a critical step in the production of hardened steel. This chapter untangles some of the complexities of the quenching process and its effect on the microstructure and properties of various steels. Making extensive use of cooling curves, it sheds light on the transformations that occur at different cooling rates and the extent to which they can be changed by adjusting quench parameters. It discusses the role of quenching in martempering and austempering along with related problems such as cracking and distortion and the challenges posed by low-hardenability steels. It also discusses the use of various quenchants, including oil, polymer, and molten salt, and explains how to measure and compare their performance using a standard (ISO 9950) test.

This chapter discusses surface engineering treatments, including flame hardening, induction hardening, high-energy beam hardening, laser melting, and shot peening. It describes the basic implementation of each method, the materials for which they are suited, and their effect on surface metallurgy.