Microstructural characterization of autogenous laser welds on 316L stainless steel using EBSD and EDS

Abstract

SummaryThis research is concerned with autogenous welding of 316L stainless steel and the microstructure generated by such a process. Autogenous welding does not require a filler material and in this case relies on an initial shallow melt phase to maintain a conduction limited weld. Essentially, a high power laser beam traverses the substrate, with the beam shaped by conventional optics, which produces a Gaussian irradiance distribution; or with a diffractive optical element, used to produce a uniform irradiance distribution.Initial results have shown that due to the nature of the heating cycle, complex microstructures are developed. These fine, complicated microstructures cannot be satisfactorily resolved and quantified using standard optical microscopy techniques. Electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS) have been carried out on a number of different microstructures prepared using a range of welding parameters. It is demonstrated that the simultaneous determination of the chemistry and crystallography is a very useful tool for rapid identification of the different phases formed on solidification as a consequence of varying welding procedures.

Characterization of a coating 316L applied by plasma transferred arc

“…Optičkom mikroskopijom je potvrđeno da je osnovni materijal (OM) toplo valjani čelik, koji posle navarivanja poseduje feritno perlitnu mikrostrukturu (Slika 6a) koja je prisutna i u zoni uticaja toplote (grubozrni ZUT, Slika 6b). Mikrostruktura poprečnog preseka deponovanog sloja prevlake je ćelijsko-dendritne strukture, koja je karakteristična za ovaj tip čelika [41][42][43], Slika 6c.…”

On laser welding of thin steel sheets

“…[28][29][30] For instance, embrittlement problems were reported 31 in catalytic converters due to the formation of intermetallic phases when the braze solidifies. [32][33][34] Furthermore, the high Ni content results in the formation of austenite not suitable for resisting high temperature oxidation.…”

Weld Pool Shaping and Microstructural Control Using Novel Computer Generated Holographic Optic Laser Welding of Steel and Stainless Steel

“…To date little work has been carried out on the effect of the microstructural development within the weld however, by using holograms to shape the beam a temperature profile can be designed within the material giving refinement of the weld profile, temperature gradients and microstructural development [7]. Work by the present authors has demonstrated the development of suitable energy distributions to control the weld profile using autogenous weld passes on stainless steel [8]. This work has shown that it is possible to obtain a squarer profile in the weld bead compared to a Gaussian distribution.…”