Microstructure study of the hardening mechanism of Cr-Ni alloy deposits after flame heating for a few seconds

► Cr-Ni alloy deposits can be obtained from a trivalent Cr based plating bath. ► The Cr-rich alloy deposit was amorphous, while the Ni-rich deposit was crystalline. ► The hardness of Cr-rich alloy deposit was increased to 1450 Hv after 3-s flame-heating. ► The hardening mechanism of flame-heated Cr-rich alloy deposit was studied. ► Precipitation of C-related nanosized particles is the hardening mechanism.