Product Code: JLA_7_3_153
G. L. Goswami
A. L. Pappachan
A. K. Grover
High‐chromium ferritic alloys were produced on mild steel substrates by laser surface alloying. For this, chromium‐plated mild steel samples were treated with a pulsed Nd:YAG laser (300 W maximum power) by varying the average power level from 21.6 W to 30.0 W. The chromium content of the surface alloys was in the range of 3.0–27.0 wt%, with fairly uniform depth of alloying. Microscopy showed very fine austenite needles within elongated/equiaxed ferrite grains in the laser‐alloyed zone (LAZ). X‐ray diffraction indicated several peaks, which were identified as being from ferrite, austenite, (CrFe)7C3 and Cr23C6. Microhardness was higher in the LAZ than in substrate and varied widely depending on the chromium content. Anodic potentiostatic polarization studies in deaerated 0.1 m Na2SO4 solution showed improvement in corrosion resistance over mild steel by several orders of magnitude. Increasing chromium content in the LAZ caused shifting of the open‐circuit potential towards the more noble side and reduced the critical current density for passivation as well as the current density in the passive range.
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