This course provides a comprehensive exploration of carburised steels, focusing on the principles, processes, and industrial applications of surface hardening. It begins with the historical development of carburising and the fundamental heat treatment techniques that enhance steel properties. The course then examines the full carburising process, including process parameters, environmental conditions, and resulting microstructures. Learners will gain insight into the causes and control of distortion and residual stresses, understanding how process variables influence dimensional accuracy and component performance. The course also addresses common failure mechanisms in carburised components, including retained austenite effects, insufficient case depth, and core strength limitations. Practical solutions such as material selection, process optimisation, and stopping-off techniques are explored to prevent failure and ensure reliability. Designed for professionals and learners in metallurgy and manufacturing, this course equips participants with the knowledge to analyse, control, and optimise carburising processes in real-world industrial contexts.