A multi-pass gas metal arc weld (“GMAW”) approach is used for in-situ repair of railhead defects. A defect is removed via machining a perpendicular slot or grove in the railhead leaving the web and base unaltered. A sufficient number of GMAW passes are used to fill the slot using a weld material suitable for the particular type of parent steel, and excess weldment can be removed. Optionally, for pearlitic steel rails post-weld heat treatment can be used to cause austenization and/or quenching of the weld. The weld heat inputs and other parameters are controlled to avoid ductile and brittle fracture related morphologies.