Hardfacing alloys

High-chromium cast irons and hardfacing alloys... 

Molybdenum-based hard alloys have also been used on extruder screws. These materials are relatively soft, about 40 Rockwell C, but have good lubricity. In some instances, wear resistance with the molybdenum hardfacing improved about 500% over the more common, but harder, hardfacing compounds. Molybdenum-based hardfacing alloys are used primarily with nitrided barrels, not only in single screw... 

Hardfacing alloy for application by the thermal spraying and powder-weld processes giving a machinable deposit of similar hardness to Stellite 6. 

In both PWRs and BWRs, corrosion of the primary circuit materials is an essential factor in the buildup of contamination layers on the surfaces of the pipes and the components. The materials used in BWRs which are in contact with the reactor water and, therefore, are potential sources of radionuclides are mainly stainless steels wear-resistant hardfacing alloys such as Stellite are also present in most of the plants. Zircaloy as the material of fuel rod claddings, spacers and fuel assembly casks need not be considered in this context, because of the extremely small release of activated constituents from this material. Due to differences in temperature and environment, the mechanisms of the corrosion process and the resulting metal release rates, which contribute to the input of corrosion products into the region of the reactor core, may show differences in different regions of the plant. Thus, corrosion of materials in the water-steam cycle exhibiting H2O phase transformations and considerable temperature differences will proceed differently than in the recirculation lines and the reactor water cleanup system, which are in contact with liquid water exclusively and show comparatively small variations in operating temperature. 

Improved wear resistance (hardfacing alloys) and corrosion resistany (stainless steel or nickel-base overlays) and dimensional restoration (buildup alloys)... 

Make the eroding surface resistant to corrosion. Examples include the use of cobalt-base hardfacing alloys to resist liquid erosion, cavitation, and slurry erosion aluminum bronze hardfacing alloys to prevent cavitation damage on marine propellers or to repair props that have... 

Choose material couples that are resistant to interaction in sliding (metal-to-metal wear resistance). Hardfacing alloys such as cobalt-base and nickel-chromium-boron alloys have been used for many years for applications involving metal-to-metal wear. Other surfaceengineering options include through-hardened tool steels, diffusion (case)-hardened surfaces, selective surface-hardened alloy steels, and some platings. 

Generally, coatings selected for wear resistance require high hardness as a characteristic, thus the term hardfacing. It is believed that most hard-facing alloys develop their wear resistance by virtue of wear-resistance carbides (Ref 43). Almost all hardfacing alloys can be separated into two major groups based on chemical compositions of the primary solidified hard phases ... 

M. Scholl, R. Devanathan, and P. Clayton, Abrasive and Dry Sliding Wear Resistance of Iron-Molybdenum-Nickel-Silicon-Carbon Weld Hardfacing Alloys, Wear, Vol 135 (No. 2), 1990, p 355... 

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