Repair of Damaged Bearings Raceways by Means of Deposition Welding

Abstract

Large-diameter slewing bearings are capable of supporting high loads and moments. They find typical usage in applications requiring extensive rotational movements, such as cranes, excavators, and wind turbines. Engineered to endure significant loads, these bearings offer low friction and maintenance requirements. With diameters often reaching several meters and featuring wide raceways, large-diameter slewing bearings are important components. In case of a failure a delivery of a new bearing can take several weeks, due to their large dimensions. Therefore, a process chain was developed, which ensures the repair of damaged raceways of the large-diameter slewing bearings. Remanufacturing aims not only to prolong the lifespan of the slewing bearings but also to minimize waste, presenting a sustainable alternative to purchasing new units. The repair process chain consists of several steps. Commencing with a damaged bearing raceway, a cladding material with sufficient chemical and physical properties is applied on the damaged surface by plasma-transferred-arc welding (PTA). Afterwards the slewing bearing undergoes a heat treatment, followed by surface pre-machining to achieve the nominal dimensions. An incremental forming process is performed to adjust the rolling bearing properties and induce compressive residual stresses. The last step of the repair process chain contains service life investigation of the repaired bearings on a rolling bearing test rig. In this first study, the fundamental feasibility of the process chain was evaluated using smaller axial bearing washers of type 81212. Therefore, plasma transferred arc welding were applied to repair the damaged raceways of the bearing washers by surface cladding. Following the repair, the bearing washers underwent a heat treatment process. Challenges in repair welding can arise from various factors, including the type of material being repaired, the location and accessibility of the repair area, and the required level of precision and quality. The repair welding process was evaluated according to different criteria. To evaluate the quality of the welding processes the repaired bearings were examined by using metallography, scanning ultrasonic microscopy, scanning electron microscopy, 3D scanning and x-ray diffraction. Furthermore, hardness measurements were carried out to investigate the properties and characteristics of the cladded layer and base material. The investigations demonstrated the feasibility of repairing the damaged raceways and showed that the new cladded raceway could welded without any macro pores or other defects.

Keywords

• plasma transferred arc welding
• repair welding
• collaborative research centre 1153
• bearing fatigue life
• tribology
• slewing bearing