HITACHI AND NIMS DEVELOP A METHOD FOR REPAIRING USED GEARS BY LASER HARDENING

Hitachi Construction Machinery Co. Ltd. and the National Institute for Materials Science ("NIMS") announced that they have jointly developed a method for repairing the wear-damaged part of used gears by laser hardening of the gear surface. Hitachi Construction Machinery and NIMS have also demonstrated that this method, which is used on gears that have been carburized by carbon diffusion to harden the metal surface, has the potential to extend the service life of the repaired gears as long as or longer than a new one.

Hitachi Construction Machinery will apply this method to the remanufacture of used gears from hydraulic pumps from April 2023, enabling an approximate 25% improvement in the rate of remanufacture and usage of gears destined for scrapping. In the case of a 20-ton hydraulic excavator, if remanufactured gears are always used instead of new ones during scheduled parts replacements, this method is estimated to have the potential to cut CO2 emissions generated in the manufacture of new parts by 13kg per excavator.

Hitachi Construction Machinery collects genuine used parts (e.g. hydraulic cylinders, hydraulic pumps and drive equipment) from customers when machines are repaired or parts are subject to scheduled replacement. The collected parts are then disassembled and serviced and supplied as remanufactured parts with the same function warranty as new parts. With long use, the gears, which are subject to heavy loads, become fatigued due to wear, residual stress, etc., resulting in deformation and breakage when they reach the end of their useful life. Hitachi Construction Machinery has demonstrated that, by applying a laser to the carbonized gear and partially modifying the surface structure to restore the hardness of the metal, which is one of the causes of malfunction, it is possible to extend the lifespan of gears as long as or longer than a new one.

Development of the method has been under way since 2020, following on from the toothed gear reusability evaluation method by x-ray radiation measurement, a collaborative project which was launched in 2019 and announced in May 2021. Going forward, Hitachi Construction Machinery and NIMS will continue to contribute to efforts to reduce their impact on the environment.