Investigations into the damage mechanisms of form fixture hardening tools

In metal forming operations such as form fixture hardening, the interaction between the tools and the work-piece is strongly influenced by the tribological properties at the interface. Damage or excessive wear of the tools can be detrimental to the quality of the final component and it also has an impact on the process economy due to increased maintenance or more frequent replacement of tools. The objective of this study was to investigate the damage mechanisms encountered in real form fixture hardening tools in order to understand the causes of tool failure and ultimately to come up with possible solutions for this problem.Advanced techniques such as scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) were used for obtaining an in-depth understanding of the different phenomena involved in the failure of form fixture hardening tools. Two different tools having different hardness values and microstructures that had been used in production were analysed.The damage mechanisms found included abrasive and adhesive wear, material transfer, corrosion and mechanical and thermal fatigue. The main damage mechanism was found to be cracking caused by mechanical stresses on the surface. Although both tools presented similar types of damage, the severity was different and it was strongly influenced by the microstructure.

► We identify the failure modes of actual form fixture hardening tools.
► Two tool steel microstructures are considered; martensitic and ferritic.
► High friction causes mechanical fatigue on tools, no thermal fatigue was observed.
► Adhesive wear and corrosion are identified as other main wear mechanisms.