Predictable Thermal Processes

© FraunhoferIWM
Light-microscopic image of the different microstructural zones of a welded joint.

To achieve the desired mechanical, chemical, and physical properties of components in thermal processes such as welding, casting, hardening, sintering, and laser melting, a thorough understanding of the diffusion, recrystallization, and phase transformation processes occurring within the materials is required. This is crucial for process control and, ultimately, the durability, strength, and resistance of components.

Examples of specific challenges we address in our projects:

  • Temperature control in heat treatment
  • Achieving desired microstructures
  • Phase separation and diffusion processes in multiphase alloys
  • Residual stress management and distortion control
  • Porosity and density control during sintering
  • Parameter tuning in selective laser melting

Predictable Thermal Processes — Use Cases

We make materials predictable. In our application examples, we demonstrate how we work and how our various R&D services work together to create a comprehensive solution.

 

Optimized steel surfaces through laser resurfacing

Laser resurfacing of steel surfaces is an attractive method for improving the wear resistance, hardness, or corrosion resistance of surfaces. It allows damaged surfaces to be repaired and materials to be applied in a targeted manner.

 

Materials and residual stress conditions in induction hardening

When induction hardening large components, such as bearing rings in wind turbines, the component is often heated using a moving inductor due to its size. This allows for targeted improvements in wear resistance and service life.

 

Optimized precipitation hardening of copper alloys

Precipitation hardening is a crucial mechanism for improving the mechanical properties of materials, particularly Cu alloys, which require not only high strength but also high electrical conductivity. Especially in contact materials for connectors, small, finely distributed precipitates in a homogeneous mixed-crystal matrix are required to meet the requirements for strength, relaxation properties, and conductivity.

 

Internal stresses in offshore jacket pipes used to predict fatigue strength

Internal stresses in large jacket pipes play a crucial role in the structural integrity of offshore wind turbines. Due to their complex geometry, internal stresses are difficult to determine; however, given the long required service life and climatic stresses, knowledge of these stresses is of great importance for safe component design.

 

Residual stress analyses of laser welds

Due to the high temperature gradients and rapid cooling rates involved in laser welding, complex residual stresses develop that can lead to warping, cracking, or reduced component strength. The challenge lies in precisely measuring and evaluating these residual stresses to ensure the reliability and service life of the welded components.

 

Reliablej Al-Cu joints via magnetic pulse welding

Due to its excellent electrical conductivity and formability, copper is the standard material for electrical wiring, but it is more expensive and heavier than aluminum. In electromobility, therefore, aluminum and copper are used in parallel and must be joined at specific points in a way that ensures both material bonding and electrical conductivity. The oxide layers that spontaneously form on aluminum and the intermetallic phases at the joint can cause significant difficulties.

 

Minimizing the risk of cold cracks during welding

Cold cracks frequently occur when welding high-strength steels, which can significantly compromise component safety. These cracks usually develop locally in the weld zone due to the interaction of microstructure, residual stresses, and hydrogen pickup.

 

Damage mechanisms in structural steel welded joints

The crack initiation phase in welded joints—that is, where cracks form and how they grow—is of central importance for assessing component safety. Due to the heat input generated during welding, several microstructural zones (base metal, heat-affected zone, weld bead) with different mechanical properties form side by side. Precise knowledge of crack initiation is necessary, as the fracture-mechanical fatigue life assessment is based on an existing crack with a defined depth and width.

 

Degassing heat treatment for electroplated components

Degassing heat treatment is used to drive hydrogen out of electroplated components in order to prevent hydrogen embrittlement. Such heat treatments are usually based on experimental trials, with guidelines regarding temperatures and treatment times often being imprecise. This leads to conservative, time and cost-intensive processes that do not adequately account for the specific coating-substrate system and component geometry.