Diffusion Analyses Using GDOES Technique of the 22MnB5 Press Hardened Steel with Al-Si and Zn-Ni Coatings

Abstract

The hot stamping process consists to heat the steel blank, at total austenitization temperatures and to transfer it into the press tooling for forming and fast cooling to fully martensitic transformation. This transference from furnace to press stage promotes some steel oxidation. The application of metallic coatings avoids this phenomenon. The Al-Si coating, a patented process, has been the most applied on steel. Hence, alternative coatings like Zn-Ni are under development. It is known that this furnace heating causes chemical elements diffusion that results in intermetallics formation. This study had the objective of analyze the diffusion profiles of chemical elements present in the substrate, 22MnB5 steel, and coatings of Al-Si and Zn-Ni, using glow-discharge optical emission spectroscopy - GDOES and to correlate the results with those obtained with energy dispersive X-ray spectroscopy - EDS. The results showed that for the Zn-Ni sample, the Zn and Fe profiles at the interfacial zone, are predominant; which justify the high proportion of ZnFe phases as showed using scanning electron microscopy - SEM images. For the Al-Si sample at the interfacial zone, the profile of Al and Fe varies simultaneously; besides that, silicon diffusion in the substrate is more effectively than the nickel diffusion. For this reason, it was possible to identify AlFeSi phase near to the steel substrate.

Study of Patchwelded Blanks Resistance Spot Welding (RSW) Before Hot Stamping with and without Heat Treatment Parameters

“…The samples chosen for X-ray diffraction are indicated in Figure 5. The detrimental effect of H on the mechanical properties and diffusion of AHSS was specifically considered by some researchers 15,[21][22][23][24][25] and fewer studies related to 22MnB5 steel press hardening steel are developed 14 and even less on 22MnB5 steel with Al-Si coating patch weld. However, the Vickers hardness results on the patchweld indicate the same possible behavior on the welding parameters used in this experiment.…”

“…As expected, hot-stamping steel, characterized by a completely martensitic microstructure and very high strength levels (ultimate tensile strength (UTS) of approximately 1600 MPa), shows a very high embrittlement index. The degradation of mechanical properties is marked; for example, the strength of a notched specimen with a hydrogen concentration of approximately 9 ppm (mass parts per million) is approximately 400 MPa, with a strength reduction of more than 75% 15 .…”