Abstract
Cracks are surface or subsurface fissures that develop in a material. Propagation energy derived from mechanical, thermal,
chemical, and metallurgical effects, or a combination of these may influence crack initiation and growth. Various types of cracks
exist in metals and can be categorised as cooling, solidification, centreline, crater, grinding, pickling, heat treatment, machining
tears, plating, fatigue, creep, stress corrosion and hydrogen cracks. Cracks can grow and lead to complete fracture of the component
posing significant threats to component life and may lead to serious injuries or loss of life. Brittle fracture in metals occurs with
little or no visible warning. Discovery of any cracks warrants immediate interventions to arrest the cracks before they propagate to
the point of fracture. Several crack detection and repair methods in metals have been developed, characterised and validated through
research. This paper reviews the repair techniques of cracks in metals.