Ni-based Alloys

Representative set of weldments was examined site welds (with pearlitic type weld metal) and two types of site weld repair zones with different welding technologies using Cr-Ni filler metals and Ni-based alloy. Results of AUGUR 4.2 inspection were compared with manual ultrasonic inspection ones in terms of defect detection, characterization, positioning and sizing in order to estimate correlation between these data. 

Molybdenum carbide is also used in TiC—Ni-based alloys and in titanium carbonitride-based cermets for metal-cutting appHcations. 

Nonferrous alloys account for only about 2 wt % of the total chromium used ia the United States. Nonetheless, some of these appHcations are unique and constitute a vital role for chromium. Eor example, ia high temperature materials, chromium ia amounts of 15—30 wt % confers corrosion and oxidation resistance on the nickel-base and cobalt-base superaHoys used ia jet engines the familiar electrical resistance heating elements are made of Ni-Cr alloy and a variety of Ee-Ni and Ni-based alloys used ia a diverse array of appHcations, especially for nuclear reactors, depend on chromium for oxidation and corrosion resistance. Evaporated, amorphous, thin-film resistors based on Ni-Cr with A1 additions have the advantageous property of a near-2ero temperature coefficient of resistance (58). 

Table 25. Properties of Precipitation Hardened Cu—Ni—Base Alloys...

For resistance against fatigue, Nimonic 75 has been used with Nimonic 80 and Nimonic 90. Nimonic 75 is an 80-20 nickel-chromium alloy stiffened with a small amount of titanium carbide. Nimonic 75 has excellent oxidation and corrosion resistance at elevated temperatures, a reasonable creep strength, and good fatigue resistance. In addition, it is easy to press, draw, and mold. As firing temperatures have increased in the newer gas turbine models, HA-188, a Cr, Ni-based alloy, has recently been employed in the latter section of some combustion liners for improved creep rupture strength. 

The Ni-base alloy surface is exposed to an oxidizing gas, oxide nuclei form, and a continuous oxide film forms (Ni) (Cr203, etc.)- This oxide film is a protective layer. The metal ions diffuse to the surface of the oxide layer and combine with the molten Na2S04 to destroy the protective layer. Ni2S and Cr2S3 results sulfidation) ... 

Fig. 3.67 Changes in corrosion rates of amorphous Fe-, Co- and Ni-base alloys measured in I N HCl at room temperature as a function of alloy chromium content "...

Nickel (Ni)/Copper (Cu)/Zinc (Zn) Nickel exhibits a mixture of ferrous and nonferrous metal properties, and Ni-based alloys are characterized by corrosion resistance. Therefore, Ni has been widely used in stainless steel (about 65% of the Ni consumed in the Western World) and superalloys/nonferrous alloys (12%). Turbine blades, discs and other critical parts of jet engines and land-based combustion turbines are fabricated from superalloys and Ni-based superalloys. The remaining 23% of consumption is applied in alloy steels, rechargeable batteries, catalysts and other chemicals, coinage, foundry products, and plating (USGS, 2006). 

Corrosion resistant fiber-reinforced plastic (FRP), 12 273-274 Corrosion-resistant Ni-base alloys, 13 513-515... 

Fabry-Perot cavity, 14 849, 850 Fabry-Perot etalons, 11 151, 152 Face-centered cube lattice, 8 114t Face-centered cubic (FCC) crystal structure in Ni-base alloys, 13 512 of spinel ferrites, 11 60 Facial makup, 7 846-847 Facial preparations, 7 842t Facial tridendate ligand, 7 578 Facihtated transport, 15 826-827 carrier, 15 845-846... 

Fe-, Co-, Ni-based alloys of this group are also commercially important for their soft-magnetic properties. 

Table 2 gives the tensile properties of the alloys. Nano-/ strengthened Fe-based alloys 75 and 90 and 100 have the excellent combination of hydrogen resistance, high strength at room temperature, high temperature strength. The properties of Fe-based alloys are better than that of the commercial Ni-based alloys. 

The general features described above for the metal dusting corrosion of Inconel 600 can also be extended to the other Ni based alloys except that the corrosion intensity decreases with increase of Cr content. The rate of corrosion is also a strong function of temperature. The maximum local metal dusting rate is plotted as a function of temperature in Fig.5. It is interesting to note that a maximum in... 

Figure 5. Temperature vs. corrosion rate for Ni-base alloys.

Figure 6. Corrosion stages for Ni-base alloys in Regime I.

E. Pippel, J. Woltersdorf and R. Schneider, Micromechanisms of Metal Dusting on Fe-base and Ni-base Alloys, Materials and Corrosion, 49 309-316 (1998). 

J. Klower, H. J. Grabke and E. M. Muller-Lorenz, Metal Dusting of Ni-based Alloys, Materials and Corrosion, 49 328-329 (1998). 

S. Strauss, R. Krajak and H. J. Grabke, Coking by Metal Dusting of Ni-base Alloys, Materials and Corrosion, 50 622-627 (1999). 

Y. Nishiyama, N. Otsuka and T. Kudo, Metal Dusting Behavior of Cr-Ni Steel and Ni-base Alloys in a Simulated Syngas Mixture, Corrosion Science, 48 2064-2083 (2006). 

The data in Table 6-1 provide a chronology of the evolution in cell component technology for MCFCs. In the mid-1960s, electrode materials were, in many cases, precious metals, but the technology soon evolved to the use of Ni-based alloys at the anode and oxides at the cathode. 

Earlier work on systems such as Ni-Al-Cr reported in Sanchez et al. (1984b) used FP methods to obtain information on phases for which there was no experimental information. In the case of Ni-base alloys, the results correctly reproduced the main qualitative features of the 7 — 7 equilibrium but cannot be considered accurate enough to be used for quantitative alloy development. A closely related example is the work of (Enomoto and Harada 1991) who made CVM predictions for order/disorder (7 — 7 ) transformation in Ni-based superalloys utilising Lennard-Jones pair potentials. 

Ni base alloys with additions of Cr and Mo are widely used as long-term corrosion-resistant metals as e.g. for containers of nuclear waste. For this reason Ni20Cr and... 

The EPR technique has been used for other alloys as well, including cast (36) and wrought (37,38) duplex stainless, as well as Ni-base alloys (39). Lee (38) used DL-EPR testing to determine the minimum amount of Ti and/or Nb required to render Type 430 SS immune from intergranular attack. In some cases, the details of the experimental method (i.e., solution temperature, KCNS and H2S04 concentrations, scan range) must be modified to differentiate best the levels of sensitization of interest. For example, Scully and Kelly doubled the... 

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