Carburising is the process of increasing the carbon content of a metal's surface layer, typically through the diffusion of carbon into the material. There are a few synonyms that can be used for carburising, such as carbonizing, carbon enrichment, or surface carburization. These terms are often used interchangeably in the industry and refer to the same process of adding carbon to the surface layer of a metal to improve its strength and durability. Other related terms include case hardening and surface hardening, which also involve subjecting a metal to high heat and carbon-rich environments to achieve the desired properties.