The sulfidation behavior of Ni-Mo alloys and Ni-Mo alloys containing various ternary additions

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:6074632

Chen, Ming-Feng

The sulfidation behavior of Ni-Mo alloys has been studied over the temperature range of 550 to 800{degree}C at a sulfur pressure of 0.01 atm. The sulfidation of various ternary alloys has also been studied in which ternary additions of Cr, Mn, Ti, V, and Al have been added to the binary alloys. The effect of sulfur-pressure was investigated at Ps{sub 2}=10{sup {minus}4} and 10{sup {minus}2} atm using two Ni-Mo-Al alloys. The sulfidation of Ni-Mo alloys followed the parabolic rate law fairly well. The sulfidation rate decreased with increasing Mo content. Scales were bi-layered, consisting of an outer layer of nickel sulfide and an inner layer of MoS{sub 2} plus intermetallic particle. The rate-controlling step of the sulfidation for the binary alloys was inward sulfur diffusion and/or outward nickel diffusion through the MoS{sub 2} layer. Neither selective sulfidation nor internal sulfidation were observed. No significant difference in the sulfidation behavior could be noted between single-phase alloys and two-phase alloys. Markers were always found at the interface between inner and outer layers. Ternary alloys generally sulfidized slower than binary alloys. Al was by far the most effective addition. For Ni-Mo-Al alloys, sulfidation kinetics was no a function of sulfur pressure. All ternary alloys followed the parabolic rate law. Complex scales formed on all alloys, consisting of an outer layer of nickel sulfide and complex inner layers. A ternary sulfide, Al{sub 0.55}Mo{sub 2}S{sub 4} and Al{sub 2}S{sub 3} were observed for the Al-containing alloys. The presence of the mixed sulfide was associated with the low sulfidation rates, and may be attributed to the combined presence of both Al{sub 2}S{sub 3} and Al{sub 0.55}Mo{sub 2}S{sub 4}.

• Research Organization: California Univ., Los Angeles, CA (USA)
• OSTI ID: 6074632
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
ALLOY SYSTEMS
ALLOYS
ALUMINIUM ALLOYS
BINARY ALLOY SYSTEMS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
DIFFUSION
ELEMENTS
KINETICS
MANGANESE ALLOYS
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NONMETALS
REACTION KINETICS
SCALING
SULFIDATION
SULFUR
TERNARY ALLOY SYSTEMS
TITANIUM ALLOYS
VANADIUM ALLOYS