Investigation of the prediction accuracy of a finite element analysis model for the coating thickness in cross-wedge rolled coaxial hybrid parts

The Collaborative Research Centre 1153 (CRC 1153) "Process chain for the production of hybrid high-performance components through tailored forming" aims to develop new process chains for the production of hybrid bulk components using joined semi-finished workpieces. The subproject B1 investigates the formability of hybrid parts using cross-wedge rolling. This study investigates the reduction of the coating thickness of coaxially arranged semi-finished hybrid parts through cross-wedge rolling. The investigated parts are made of two steels (1.0460 and 1.4718) via laser cladding with hot-wire. The rolling process is designed by finite element (FE)-simulations and later experimentally investigated. Research priorities include investigations of the difference in the coating thickness of the laser cladded 1.4718 before and after cross-wedge rolling depending on the wedge angle β, cross-section reduction DA, and the forming speed v. Also, the simulations and the experimental trials are compared to verify the possibility of predicting the thickness via finite element analysis (FEA). The main finding was the ability to describe the forming behavior of coaxially arranged hybrid parts at a cross-section reduction of 20% using FEA. For a cross-section reduction of 70% the results showed a larger deviation between simulation and experimental trials. The deviations were between 0.8% and 26.2%. © 2019 by the authors

Tribological study on tailored-formed axial bearing washers

To enhance tribological contacts under cyclic load, high performance materials are required. Utilizing the same high-strength material for the whole machine element is not resource-efficient. In order to manufacture machine elements with extended functionality and specific properties, a combination of different materials can be used in a single component for a more efficient material utilization. By combining different joining techniques with subsequent forming, multi-material or tailored components can be manufactured. To reduce material costs and energy consumption during the component service life, a less expensive lightweight material should be used for regions remote from the highly stressed zones. The scope is not only to obtain the desired shape and dimensions for the finishing process, but also to improve properties like the bond strength between different materials and the microscopic structure of the material. The multi-material approach can be applied to all components requiring different properties in separate component regions such as shafts, bearings or bushes. The current study exemplarily presents the process route for the production of an axial bearing washer by means of tailored forming technology. The bearing washers were chosen to fit axial roller bearings (type 81212). The manufacturing process starts with the laser wire cladding of a hard facing made of martensitic chromium silicon steel (1.4718) on a base substrate of S235 (1.0038) steel. Subsequently, the bearing washers are forged. After finishing, the surfaces of the bearing washers were tested in thrust bearings on an FE-8 test rig. The operational test of the bearings consists in a run-in phase at 250 rpm. A bearing failure is determined by a condition monitoring system. Before and after this, the bearings were inspected by optical and ultrasonic microscopy in order to examine whether the bond of the coat is resistant against rolling contact fatigue. The feasibility of the approach could be proven by endurance test. The joining zone was able to withstand the rolling contact stresses and the bearing failed due to material-induced fatigue with high cycle stability

Numerical simulation and experimental validation of the cladding material distribution of hybrid semi-finished products produced by deposition welding and cross-wedge rolling

The service life of rolling contacts is dependent on many factors. The choice of materials in particular has a major influence on when, for example, a ball bearing may fail. Within an exemplary process chain for the production of hybrid high-performance components through tailored forming, hybrid solid components made of at least two different steel alloys are investigated. The aim is to create parts that have improved properties compared to monolithic parts of the same geometry. In order to achieve this, several materials are joined prior to a forming operation. In this work, hybrid shafts created by either plasma (PTA) or laser metal deposition (LMD-W) welding are formed via cross-wedge rolling (CWR) to investigate the resulting thickness of the material deposited in the area of the bearing seat. Additionally, finite element analysis (FEA) simulations of the CWR process are compared with experimental CWR results to validate the coating thickness estimation done via simulation. This allows for more accurate predictions of the cladding material geometry after CWR, and the desired welding seam geometry can be selected by calculating the cladding thickness via CWR simulation. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Studies on the robustness of underwater laser cutting of S355J2+N using a Yb:YAG disk laser source

In this paper, an underwater laser cutting process for maintenance and replacement operations is presented and investigated regarding process robustness for the application in rough environments. A Yb:YAG laser is used with 4 kW laser power in an active cutting process with oxygen as cutting gas. For 10 mm thick constructional steel plates a process window is determined with the focus on robustness for distance interferences. The examined parameter sets include the nozzle clearance, focus positioning and cutting gas pressure adjustment, as they are significant factors of influence in underwater laser cutting. By adjusting the developed parameter sets, sheets with thicknesses up to 50 mm, as well as plates that are fixed to a concrete backing are cut. The used equipment, which completely consists of standard components, is presented along with its preparation for underwater operation

Manufacturing of High-Performance Bi-Metal Bevel Gears by Combined Deposition Welding and Forging

The present paper describes a new method concerning the production of hybrid bevel gears using the Tailored Forming technology. The main idea of the Tailored Forming involves the creation of bi-metal workpieces using a joining process prior to the forming step and targeted treatment of the resulting joint by thermo-mechanical processing during the subsequent forming at elevated temperatures. This improves the mechanical and geometrical properties of the joining zone. The aim is to produce components with a hybrid material system, where the high-quality and expensive material is located in highly stressed areas only. When used appropriately, it is possible to reduce costs by using fewer high-performance materials than in a component made of a single material. There is also the opportunity to significantly increase performance by combining special load-tailored high-performance materials. The core of the technology consists in the material-locking coating of semi-finished parts by means of plasma-transferred-arc welding (PTA) and subsequent forming. In the presented investigations, steel cylinders made of C22.8 are first coated with the higher-quality heat-treatable steel 41Cr4 using PTA-welding and then hot-formed in a forging process. It could be shown that the applied coating can be formed successfully by hot forging processes without suffering any damage or defects and that the previous weld structure is completely transformed into a homogeneous forming-typical structure. Thus, negative thermal influences of the welding process on the microstructure are completely neutralized

Review on Laser Deposition Welding: From Micro to Macro

Laser cladding has become an established technology for parts repair and surface modification for cost-intensive components. Due to ongoing improvements of laser sources, process technology and strategy, the range of applications for laser deposition processes is continuously increasing. Critical issues as well as performance and economic efficiency problems have been solved in recent years. Consequently big advances have been done in laser cladding, from micro to macro, from low- to high power as well as in hybrid processes