Corrosion resistance of laser surface modified Alloy 600

Intergranular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC) behaviors of the laser surface modified Alloy 600 containing 0.04%C or 0.06%C have been investigated. YAG laser beam was used as a heat source for surface melting or alloying of thermally sensitized Alloy 600. Two filler wires were used for laser surface alloying process. IGC resistance was evaluated by Stretcher test (Exposure in boiling 4oomlH2O-233mlH2SO4-50gFe2(SO4)3 for 6h or 24h). IGSCC resistance was evaluated by crevice d bent beam test (Exposure in 288degC hot water containing 8 ∼ 9 ppm DO for 500h with 2% bending strain). The results obtained are as follows:(1) The IGC and IGSCC resistance of the laser surface melted Alloy 600 depends on carbon content. (2) In the case of 0.04%C Alloy 600, corrosion resistance can be slightly increased by laser surface melting. And in the case of 0.06%C Alloy 600, corrosion resistance is decreased by laser surface melting. (3) The corrosion resistance of the sensitized 0.06%C Alloy 600 can be remarkably increased by the laser surface alloying, in which Cr, Mo, Ti, Nb-rich filler wires are used. (author)