The Transportation Technology Center is currently evaluating methods to improve the performance of rail welds. Among the strategies being investigated is a post-weld heat treatment that uses manual welding. With this approach, a high-hardness welding electrode is used to deposit a weld bead covering the softest portion of the heat-affected zone (HAZ) of the primary rail weld. The technique, termed HAZ Overlay Treatment (HAZOT), has been applied to treat standard and head alloyed thermal welds. Tests are under way to evaluate the effectiveness of HAZOT in revenue service. Other ongoing tests include induction heat-treated electric flash-butt welds, HAZOT electric flash-butt welds and full section alloy thermite welds. Reports that HAZ overlay treatment was concluded to be effective until the depth of the treatment has been surpassed by normal rail wear and grinding. Therefore, alternative methods of HAZ treatment of both thermite and electric flash-butt welds are being discussed to replace the HAZ overlay treatment.
Railway Track & Structures, July 2017, pp.14-16.