Surface texturing of forming tools by laser implantation
Source: BAM, Division Welding Technology
Since it is of great relevance to reduce friction and minimize wear, texturing represents one of the main research topics in surface science nowadays. Surface texturing methods aim to tailor the interaction behavior of contacting surfaces by changing their microgeometry. Although the potential of protruded microstructures (e.g. in deep-drawing) is still known, their application is still limited. Since protruded microstructures are predominantly affected by wear, an economical structuring process which enables the formation of deterministic textures with a high wear resistance is needed.
To overcome this issue one promising approach is given by the laser implantation process. This surface engineering technology enables the formation of protruded microfeatures with wear resistant properties in one processing step by a localized laser dispersing of ceramic particles. Due to the local volume increase caused by the inserted particles, separated microfeatures can be created on steel surfaces. The geometry of the so-called implants can be adjusted by the processing parameters. Due to the high flexibility of the process, single separated features can be arranged in deterministic pattern where needed. Since a pre-placed coating is used to supply the ceramic particles to the laser process, an economic texturing by scanner-optics may also be possible. Therefore, the laser implantation technique shows enormous potential as texturing method even for large scale or complex forming tools.
In this paper the localized dispersing behavior of TiB2 particles in AISI D2 cold-work tool steel was studied. It was found that defect-free dome- or ring-shaped implants with diameters up to ~400 µm and heights up to ~30 µm can be developed. Regarding the material properties it was found that the implants show very high hardness values up to 1800 HV1 (initial substrate hardness ~600 HV1). These unique properties evolving from the Metal-Matrix-Composite which is formed by the tool steel matrix and the embedded TiB2 primary particles. Furthermore, in-situ precipitated TiC secondary particles were found, which diminish the retained austenite content of the matrix.
Dispersion behavior of TiB2 particles in AISI D2 tool steel surfaces during pulsed laser dispersing and their influence on material properties
Felix Spranger, Kai Hilgenberg
published in Applied Surface Analysis 2019, Volumes 467 - 468, Pages 493 - 504
BAM, Division Welding Technology