Product Code: JLA_5_2_23

Authors:
Dilip Kumar
K. Sridhar
A. R. Biswas
G. L. Goswami
M. B. Deshmukh

High Mo surface alloys on stainless steels 304L and 316L were produced by laser surface alloying. For this, a layer of 60 μm thickness was overlaid on the substrates by plasma spraying of Mo powders. These were further treated by a Nd:YAG pulsed laser for alloying. Depths of alloying in the range of 440–1110 μm were achieved. Concentration in the range of 5.2–15.0 wt% Mo within the laser alloyed zone was, in general, uniform throughout. During alloying, in‐situ heating at 700°C was required to prevent cracking in samples with 5.2–6.0 wt% Mo. Higher Mo content enhanced the cracking tendency and made it difficult to prevent cracking completely even at this temperature. Fully austenitic microstructure of the substrate metals transformed to austennitic‐ferritic duplex for 5.2–9.0 wt% Mo and to fully ferritic for 15.0 wt% Mo. Primary solidification mode also changed to FA, FA + F and finally to F depending upon Mo content in the alloyed zone. Ferrite content in the alloyed zone was in the range of 31–79% depending upon amount of Mo.Microhardness was increased from 173 VHN for 316L to 198–790 VHN depending upon wt% Mo in the alloyed zone. Preliminary studies indicated that pitting potential in 3.5% NaCl aqueous solution improved substantially from 132 mV for 304L and 240 mV for 316L to 480 mV and 500 mV respectively for 5.5–6.0 wt% Mo in the alloyed zone.