Nickel-based Hardfacing Alloys Research Articles

Evaluation of new ferro-phosphorus powders

In this work we examine the microstructure and the hardness of the nickel-base hardfacing alloy and their influence on the wear resistance of a deposited layer when different alloy elements were added. Based on the results in this study, we can conclude the following: (1) niobium can reduce friction and wear loss of a deposited layer; (2) when molybdenum and carbon were added, they will combine and form a coarse precipitate that exhibits excellent wear resistance to the deposited layer against Si3N4 ceramic ball wear test under the dry wear condition; and (3) under oil lubrication, the wear debris accumulate and form a protective layer on the worn surface. If such a protection layer is derived from a high hardness deposited layer, it will remain on the worn surface and then reduce the wear loss.

Laser cladding of nickel-based hardfacing alloys

The effects of powder feed rate (PFR) and translation speed (TS) of a laser beam were investigated on laser cladding with three nickel-based hardfacing alloys: Colmonoy 6, Colmonoy 88 and AI-1236. The width-to-height ratio of single clad passes and the extent of dilution were found to decrease with increasing PFR and decreasing TS. Microstructurally, Colmonoy 6 clad layers consisted of a nickel-based structure of primary γ-nickel dendrites and interdendritic eutectics of γ-nickel, nickel borides and nickel silicides, Colmonoy 88 of mixed carbides and AI-1236 of partially melted WC particles and mixed carbides embedded in similar nickel-based microstructures. Block-on-ring wear tests showed that the wear mechanism is largely abrasive in nature for all three alloys studied. The wear resistance was found to correlate better with the type and amount of the main hard phase present in the clad layer: AI-1236 clad layers were much superior to those of Colmonoy 6 and Colmonoy 88 clad layers owing to WC particles in the alloy.

Microstructures of laser-clad nickel-based hardfacing alloys

Distinctive microstructures of laser-clad passes with three nickel-based hardfacing alloys were observed. The boride-hardened Colmonoy 6 consisted of a structure of γ-nickel dendrites and interdentritic eutectics of γ-nickel, nickel borides and nickel silicides; carbide-hardened Colmonoy 88 consisted of mixed carbides, while WC-strengthened AI-1236 consisted of partially dissolved WC particles embedded in a similar microstructure to Colmonoy 6. For a given laser beam intensity, the microstructures of the clad layers are significantly influenced by the powder feed rate (PFR) employed and, to a lesser extent, the translation speed (TS) of the laser beam. A cellular-to-dendritic transition for Colmonoy 6, a morphology change of the mixed carbide from coarse leaf-like to fine, equiaxed but angular shape for Colmonoy 88, and a lesser degree of dissolution of WC particles for AI-1236 occurred with increasing PFR. At sufficiently high TS, the nucleation and growth of the mixed carbide phases in the Colmonoy 88 layer can be suppressed, especially when the PFR is low. The effect of PFR and TS on the clad microstructure can be understood in terms of the specific energy input ( E S) and the specific heat energy ( E h) available, respectively.

The influence of niobium, chromium, molybdenum and carbon on the sliding wear behavior of nickel-base hardfacing alloys

In this work we examine the microstructure and the hardness of the nickel-base hardfacing alloy and their influence on the wear resistance of a deposited layer when different alloy elements were added. Based on the results in this study, we can conclude the following: (1) niobium can reduce friction and wear loss of a deposited layer; (2) when molybdenum and carbon were added, they will combine and form a coarse precipitate that exhibits excellent wear resistance to the deposited layer against Si 3N 4 ceramic ball wear test under the dry wear condition; and (3) under oil lubrication, the wear debris accumulate and form a protective layer on the worn surface. If such a protection layer is derived from a high hardness deposited layer, it will remain on the worn surface and then reduce the wear loss.

Preparation and characterization of melt-spun nickel-based alloys containing heavy metals

The solidification behaviour and morphology of some nickel-based hardfacing alloys containing heavy metals such as tungsten have been studied by scanning electron microscopy and transmission electron microscopy. These alloys are very sensitive to different cooling rates (from as cast to melt spinning). At low cooling rates, these alloys present as primary phases, i.e. the stable carbide M 7C 3 or the double carbide M 6C (η type), according to the silicon content. For high cooling rates, the alloys occur as either amorphous (high silicon content) or microcrystallized structures depending on silicon level. In this latter case, the solid solution Ni(α) and the metastable carbide M 23C 6 are observed.

The metallurgical structure of as-solidified Ni-Cr-B-Si-C hardfacing alloys

The crystallization of complex nickel-base hardfacing alloys is studied with reference to the ternary Ni-Si-B and quaternary Ni-Cr-B-Si systems. Quenched interrupted, directional solidification is employed to establish the solidification sequence. The transformation temperatures are measured by differential thermal analysis. Solid-state transformations occurring during the cooling process are described. A model of the solute exchanges during solidification is proposed in order to predict the amount of liquid remaining at each stage in the process, particularly at the last stage when all the eutectic liquid is frozen in.

Tribological coatings for liquid metal and irradiation environments

Several metallurgical coatings have been developed that provide good tribological performances in high-temperature liquid sodium and that are relatively unaffected by neutron fluences to 6 × 1022 n/cm2 (E >0.1 MeV). The coatings that have consistently provided the best tribological performance have been the nickel aluminide diffusion coatings created by the pack cementation process, chromium carbide or Tribaloy 700 (a nickelbase hardfacing alloy) applied by the detonation-gun process, and chromium carbide and other hardfacing materials applied by the electro-spark deposition process. The latter process is a relatively recent development for nuclear applications and is expected to find wide usage. Other coating processes, such as plasma-spray coating, sputtering, and chemical vapor deposition, were candidates for use on various components, but the coatings did not pass the required qualification tests or were not economically competitive. The advantages and limitations of the three selected processes are discussed, the tribological performance of the coatings is reviewed, and representative applications and their performance requirements are described.

Coatings for fast breeder reactor components

Several types of metallurgical coatings are used in the unique environments of the fast breeder reactor. Most of the coatings have been developed for tribological applications, but some also serve as corrosion barriers, diffusion barriers or radionuclide traps. The tribological coatings must meet a variety of performance criteria for friction coefficients, wear rates, galling resistance and self-welding resistance in liquid sodium. In addition, most applications require the coating to exhibit long-term resistance to sodium corrosion, resistance to damage by thermal cycling at temperatures up to 625°C and, for core applications, resistance to irradiation damage to neutron fluences of 6 × 10 22 neutrons cm -2 or more. The materials that have consistently given the best performance as tribological coatings in the breeder reactor environments have been coatings based on chromium carbide, nickel aluminide or Tribaloy 700 (trademark of Cabot Corporation) (a nickel-base hardfacing alloy). Other coatings that have been qualified for limited applications include chromium plating for low temperature galling protection and nickel plating for radionuclide trapping. Processes now employed include detonation gun coating, diffusion coating, electrospark deposition coating and electroplating. Several plasma spray processes, sputtering and chemical vapor depositions have been candidates for use on some reactor components, but did not pass the required qualification tests or were not economically competitive with alternative coating methods.

HAYNES ALLOY No. N-6

Abstract HAYNES alloy No. N-6 is a nickel-base hardfacing alloy that combines excellent wear resistance with good corrosion resistance and good impact properties. Alloy No. N-6 does this without dependency on cobalt and with significant cost savings over the traditionally used cobalt-base alloys. HAYNES alloy No. N-6 should be evaluated for applications such as fluid valves, corn-cutting knives, glass-shearing blades and automatic applications where STELLITE alloy No. 6 has been used successfully. This datasheet provides information on composition, physical properties, and hardness as well as fracture toughness. It also includes information on corrosion and wear resistance as well as forming, heat treating, machining, joining, and powder metal forms. Filing Code: Ni-274. Producer or source: Cabot Corporation.

高温ナトリウム中における表面硬化材の摩擦特性

Friction and self-welding tests were conducted on several materials used for the contacting and sliding components of a sodium cooled fast breeder reactor. In the present study, the friction and self-welding characteristics of each material were evaluated through measuring the kinetic and breakaway friction coefficients. The influence of oscillating rotation and vertical reciprocating motion on the friction mode was also investigated.The results obtained are as follows:(1) Colmonoy No. 6, the nickel base hardfacing alloy, indicated the lowest kinetic friction coefficient of all the materials in the present study. Also, Cr3C2/Ni-Cr material prepared by a detonation gun showed the most stable friction behavior.(2) The breakaway friction coefficient of each material was dependent upon dwelling time in a sodium environment.(3) The friction behavior of Cr3C2/Ni-Cr material was obviously related with the finishing roughness of the friction surface. It was anticipated that nichrome material as the binder of the chrome carbide diffused and exuded to the friction surface by sliding in sodium.(4) The friction coefficient in sliding mode of vertical reciprocating was lower than that of oscillating rotation.

Co基，Ni基硬質材料の高温ナトリウム中における摩擦挙動について

A friction behavior of the hardfacing materials such as cobalt base alloy ''Stellite'' and nickel base alloy ''Colmonoy'' used in the sliding components of a sodium cooled fast breeder reactor was investigated in various sodium environments. Also, friction tests on these materials were carried out in argon environment. And they were compared with those in sodium environment. The results obtained are as follows: (1) In argon, the cobalt base hardfacing alloy showed better friction behavior than the nickel base hardfacing alloy. In sodium, the latter was observed to have the better friction behavior being independent of the sodium temperature. (2) The friction coefficient of each material tends to become lower by pre-exposure in sodium. Particularly, this tendency was remarkable for the nickel base hardfacing alloy. (3) The friction coefficient between SUS 316 and one of these hardfacing materials was higher than that between latter materials. Also, some elements of hardfacing alloys were recognized to transfer on the friction surface of SUS 316 material. (4) It was observed that each tested material has a greater friction coefficient with a decrease of the oxygen content in sodium.

Centrifugally cast cylinder lining alloys and their compatibility with cobalt-base and nickel-base hardfacing alloys

Wear- and corrosion-resistant coatings applied to cylinder bores by an in situ melting and centrifugal casting process are widely used in plastics processing machinery. Cylinder lining alloys and the method of manufacturing bimetallic cylinders with these alloys are described. One primary cause of cylinder wear is an internal screw which can bear heavily against the cylinder bore. Since the screw flights are often hardsurfaced with cobalt-base or nickel-base alloys, Alpha LFW-1 wear tests were made to evaluate the relative wear resistance of these alloys and their compatibility with centrifugally cast cylinder lining alloys. The results indicate preferred hardfacing materials and application processes for use with each lining alloy.