Stellite 6 is a cobalt based alloy but is very tolerant of dilution from other materials and is often used on stainless to give a wear resistant area, e. Hightemperature hardness and wear resistance of stellite alloys. The 450 series bullwhips by david morgan were used in the indiana jones movies and in the mask of zorro. Hardfacing of aisi h tool steel with stellite 21 alloy. This material is applied using the hvof process to achieve a very dense and hard coating. Because of the presence of the carbide network, the overlay is somewhat prone to cracking, although resistance to cracking is very good for an alloy of this hardness level. Since the thickness is 5mm, we have to do 2 layers.
Bonding stellite 6 to alloy steel bonding stellite 6 to alloy steel river1. A comparative study for wear resistant of stellite 6. Higher carbon stellite alloys such as stellite 6 are known to contain m 7 c 3 type carbides. This article is based on what that research team has discovered. But the alloy 21 bufferlayer hardness, which ranged from 39 to 70 rockwell c most readings were above 50, was well outside the range expected for this material. Hello, i work with valves gates, stems etc and i do a lot of overlay including 316,410 and stellite 6. Resistance to cavitation erosion nearly as good as stellite alloy 6 and as good or better at high loads. Hightemperature hardness and wear resistance of stellite.
These carbides provide high hardness level of the alloy. It is a trademarked name of the deloro stellite company and was invented by elwood haynes 1 in the early 1900s as a substitute for cutlery that stained or that had to be constantly cleaned. Grade 91 and alloy 6 had hardness values within their expectedranges. The wear test results showed that the weight loss for the coating on mild steel was. Welding tips and tricks view topic stellite 6 overlay. Hardfacing alloys and processes for advanced ultrasupercritical. This is a lower hardness version of stellite 6 and is more forgiving less crack sensitive. These bullwhips have shown good endurance and shape retention over many years of use. Alloy 6b uns r30016 ams 5894 description alloy 6b is a cobaltbased alloy with great wear, erosion and abrasion resistance. Metastable phases such as cr 23 c 6, cr 7 c 3, m 6 c are also present in the xrd patterns. Deloro stellite says the hardness of its stellite 21 typically is 27 hrc and can workharden up to 40 hrc.
Wear characteristic of stellite 6 alloy hardfacing layer. I had to develop a procedure for multi layer crack free stellite 6, applied to a multi faceted c. Further, the stellite coating on mild steel was significantly harder than that deposited on the superalloy. Stellite alloys are classified into two types based on their composition.
Many components require the application of additional layers to. The results showed less cracking and pore development for stellite 6 coatings applied to the mild steel ms substrate. The issue of whether hardfacing adversely affects the properties of duplex stainlesssteel base materials depends on several factors. Stellite alloy distributor in the usa a metal source, llc inventory consists of various stellite alloy grades in any size or form as indicated below. Evaluation of microstructure and mechanical properties at. It is able to retain these same properties at elevated temperatures. They are destined for parts lap or overlay weld stelliting. Kennametal, velan and carleton university formed a research team to evaluate new hardfacing alloys and application processes for advanced ultrasupercritical applications. Stellite 6 is a well know overlay in the pump and valve industry. Stellite 6 is a cobased coating material that possesses superior hightemperature wear. The distinctive difference between cobalt 6k proprietary name stellite 6k and cobalt 6b the alloy used in talonite is that 6k contains about 50% more carbon than 6b, making. I work with valves gates, stems etc and i do a lot of overlay including 316,410 and stellite 6. This melts the powder and creates slurry or plasma overlay on the surface.
Deposition of stellite 6 on nickel superalloy and mild. Can duplex stainless steels be hardfaced without adversely affecting the base material properties. Laser cladding was performed with a fibredelivered nd. Figure 2 demonstrates that tribaloy t800 maintains higher hardness at elevated temperatures.
Stellite alloys are often used as a weld hardfacing on valves, spindles, and other. Guidelines for stellite hardfacing onto steels page 2 of 7 march 22, 2007 carbon equivalent vs preheat temperature 0 50 100 150 200 250 300 350 0. Definition of crack the whip in the idioms dictionary. Stellites are very resistant to wear, corrosion in acidic environment and hot oxidation. It is easily deposited by a number of methods but you do have to be careful about contamination from sulphur or phosphorus. Bonding stellite 6 to alloy steel asme mechanical code. Ct5 also has good resistance to impact and cavitation erosion. Erosion test curves of stellite alloys 7 51 figure 215. How to control check cracking and use to your advantage. Alternate stellite process material selection and properties. Hardfacing a standard term for a wearresistant weld overlay is commonly used for seat and guide surfaces on valve trim of all styles. A comparative study for wear resistant of stellite 6 coatings.
The hot hardness of stellite 6 weld overlays drops off sharply as iron. Recently i have been working with a gate made out of 316 ss, and i need to build up over 18 of stellite 6. Ct52 is a cobalt based alloy, which provides excellent resistance to wear, galling, and corrosion. Stellite failure on a p91 hp valve failure investigation. This alloy is very popular since it can retain hardness even at elevated temperature. Cocrw meets or exceeds ams 5894, pwa 1196, mcs 1012 and uns r30016. The alloy currently most suited for cutting tools, for example, is stellite 100, because this alloy is quite hard, maintains a good cutting edge at high temperature, and resists hardening and annealing. Recharge by welding a carbon steel valve with inconel625 825 overlay, cladding. We took the method of smaw with the stick electrode of stellite 6. Cladding of stellite 6 co cr alloy on stainless steel for high temperature and high pressure valve applications is essential to prevent the contact surfaces from various form of wear factors 4,5. Microstructure and wear behavior of stellite 6 cladding on.
Epri has established a committee on cracking and disbonding of. The top diameter of the cone is mm,while the other is 300mm,and the thickness of the cone is 12mm duplex steel,that is sa516 gr. Yag rofin sinar laser, at 550 w, spot size 3 mm in diameter. It is known that these carbides are of the type m 23 c 6 in stellite 21. Aug 15, 20 the carbides present in the cocrwbased stellite alloys are of chromiumrich m 7 c 3 type. Today, the hardening of sealing surfaces is performed by welding a material harder than the valve body material. Due to the high cost of stellite when i got to the end of a rod id let the rod stay in the puddle then fuse my next rod onto the last and keep on trucking. Introduction 1 stellite 6 is a very versatile material that is used for hardfacing of various component parts for applications requiring wear resistance cobaltbase rods 1982. Hardfacing steel with nanostructured coatings of stellite6. Stellite 6 alloys coated on stainless steel are used for valve application in a hightemperature and highpressure environment, where a material may melt, creep, or degrade. This article provides an overview of work done to evaluate suitable alternatives to stellite 6. Oct 24, 2002 stellite 6 is a cobalt based alloy but is very tolerant of dilution from other materials and is often used on stainless to give a wear resistant area, e. If that temperature is increased to the point that cracking is alleviated, the interpass temperature required to avoid adverse effects in the duplex stainlesssteel base metal will be exceeded.
Stellite 3 is superior and this improved resistance increases as loads are increased or speeds are increased to 10 times to 25 times that of stellite alloy 6 or 12. This paper demonstrates the successful application of stellite 6 metallic coatings on the ni and febased superalloys by hvof process for hot corrosion applications. It may also contain tungsten or molybdenum and a small but important amount ofcarbon. Cobalt alloy 6b stellite 6b ams 5894 aircraft materials. A substitute for stellite on sealing surfaces guichon valves.
In other words, the overlaid surfaces met at 90 degree angles, inside and outside corners. The different process steps are coupled in order to transfer the residual conditions from preceding processes to the ones following. In our application, the working temperature is between 250degreesc and 300degreesc 6. Hpa cobalt 6b is a wear resistant alloy used for stems, balls, rails and bushings. Stellite 6 overlay on ss 316 welding tips and tricks. Microstructure and wear behavior of stellite 6 cladding on 17. The material is also resistant to erosion and most. When we finished the first stellite 6 layer, there is no cracking found. Crack the whip definition, to demand obedience, hard work, or efficiency from others in a harsh or stern manner. The material itself has been around since the 1900s and was originally seen as a substitute for traditional metal cutlery which suffered from general wear and tear and was also prone to staining.
Stellite 6 is a cobase wear resistant alloy containing 1% c, 27% cr, 4. Stellite is a family of completely nonmagnetic and corrosionresistant cobalt alloys of various compositions that have been optimised for different uses. Stellite 6b is supplied in the solution treated condition to ams 5894 and its wear resistant. Influence of yttrium additive on wear behavior of stellite 6 at elevated temperatures 25 54. Microstructure evolution and failure behavior of stellite 6. Instead of using stellite 6 overlay on smaller sizes 22cr duplex components e. Laser cladding, hvof, plasma spraying, stellite 6 coating, friction and wear, nickel alloy. Stellite alloy is a range of cobaltchromium alloys designed for wear resistance.
We are looking at huge volume, grinding time is critical. Most of the time, this material is stellite, a cobaltbase. The microstructure of stellite 6 contains hard m 7 c. I am having issues though as my tip keeps overheating, melting and fusing with the wire. Also we can apply other materials such as stellite 6 or 12 or nickel ni 100%. If one has to perform weld repairs to an existing stellite 6 hardfacing, your best approach is to use stellite 21.
Stellite definition of stellite by the free dictionary. For small, simple parts, cracking is not a usually a problem. Fisrtly, we had a 3mm thickness of 309mol overlay with fcaw. Cobalt alloy 6b stellite 6b is a cobaltbased, chromiumtungsten alloy used extensively in wear environments where its low friction coefficient minimises the risk of seizing and galling, even in applications where lubrication is not practical. This paper deals with the investigation of the microstructure and wear behavior of the stellite 6 cladding on precipitation hardening martensitic stainless steel 174ph using gas tungsten arc welding gtaw method. Check availability with our sales department by submitting your inquiry below to see if a metal source, llc can provide your stellite alloy metal requir. It looks like most of the sections can be remade for the same or less money as itd cost to attempt the stellite overlay and attendant machining. Hardfacing steel with nanostructured coatings of stellite6 by supersonic laser deposition rocco lupoi1, andrew cockburn1, chris bryan1, martin sparkes1, fang luo2 and william oneill1 the ability to manufacture coatings is critical to engineering design.
Then we have to get 5mm thickness of cocra alloy overlay. However, when we finished the second layer and let it cool gradually wrapping the cone with. Again, weld repairs to stellite 6 hardfacing should not really be performed. Evaluation of microstructure and mechanical properties at the. The cocrw system alloy retains its hardness at elevated temperatures and is especially effective for wear applications at high temperatures or in a corrosive environment, and are widely used as a wear, corrosion, and heatresistant material 43. Stellite alloys derive their high hardness from the carbides dispersed in a relatively soft cobased alloy matrix strengthened by cr and wmo. Stellite 6b hpa cobalt 6b uns r30016 high performance. Delamination failures of stellite hardfacing in power plants. Lower carbon content makes it inferior to stellite alloy 6 for low stress abrasion resistance. Dry sliding wear map for stellite 6 against a wcco 9010 disc 12 49 figure 214. A metal source, llc stellite alloysstellite alloys.
Without a heat treat oven, slow cool generally means completely burying the part in a big cat box filled. View detailed import data, price, monthly trends, major importing countries, major ports of stellite 6 wire. The sequence of the primary welding process and the following secondary processes of machining, and heat treatment has been modelled to predict the residual conditions in a stellite 6 overlay weld on a p91 steam turbine valve. Stellite 6 coating chemically etched with aqua regia. Stellite 6 welds pretty clean unless it gets oxidized and then the puddle gets sluggish.
However, when parts become larger or more complex, alloy 6 will crack unless the preheat temperature is increased. Inspect steam valves for stellite delamination welcome to. It is also possible to apply tungsten carbide containing nickel based overlay, although the high meltpool temperature places limitations on carbide size, volume fraction and binder alloy composition. Seawater applications are not suitable for stellite 6, as it is at high risk of cracking in that environment.
Pdf delamination failures of stellite hardfacing in power. Tensile strength is 758 mpa, yield stress is 655 mpa, youngs. Hard facing hf and corrosionresistancealloy cra with hot wire, materials. When field welding, stellite 21 is preferred as only modest preheat is required and because stellite 21 is more ductile, as deposited, than stellite 6. I have seen many valves refurbished in the field with stellite 21 being replaced with stellite 6.
Alloy of cobalt from 50 to 65 %, chromium from 25 to 35 %, tungsten from 4 to %, carbon from 1 to 2,5 % and other elements molybdenum, nickel, iron, titanium. Higher carbide level is associated with lower corrosion resistance, since, in. The dilution region is the region where melted substrate forms a mixture with coating material and possesses microstructure similar to the coating. The wear resistance of alloy 6b is due to the chemical composition and is not a product of heat treatment or other hardening mechanisms. The chemical composition of stellite 6 is given in table 3. Oct 10, 20 the interface area in laser cladding, microstructures and mechanical properties of which determine the structural integrity of the laserdeposited coating, consists of two distinctive zones.
Can any one suggest which is the best wheel to use for grinding stellite 6. Stellite 6 overlay on the disk contact surfaces of a dual plate check valve. Stellite 21 will work harden to develop full hardness. If this is not a critical factor and you are using a rigid setup, i see no problems in using the 60 grit with a higher infeed. Without a heat treat oven, slow cool generally means completely burying the part in a big cat box filled with vermiculite and leaving it alone at least overnight. Hardfacing alloys and processes for advanced ultra. The deposit was 500 mm figure 3 typical stellite 6 coating track crosssection on steel by supersonic laser deposition sld. The way we produce a stellite coating is by taking cobalt 6 powder, for example, and applying it to a roughmachined round andor flat metal surface using the plasma transferred arc pta method of welding. Data provided by the manufacturer, deloro stellite inc. This alloy also has higher hot hardness and resists galling like all stellite alloys when mated with another stellite alloy. The overlay had to be ground smooth and pass a penetrant test, i. Stellite 6k is one of a series of cobaltchromium alloys, which are basically a combination of cobalt 50%plus, chromium between 2530%, and several other elements. Depending on how long the weld is and how its layed out, some cracking is usually inevitable with stellite 6 its normal.
Hardfacing steel with nanostructured coatings of stellite. Pdf delamination failures of stellite hardfacing in. How to avoid stellite 6 crackings american welding society. Stellite is a nonmagnetic alloy which contains a variety of different metal components with the main elements being cobalt and chromium. The trademark owners of stellite claim that stellite 6 is the most widely used of their range of stellite alloys, offering a proven industry standard for generalpurpose wear resistance, and high mechanical and chemical perfromance in hostile environments. In such application, alloys play an important role in preventing various wear. Stellite alloys chemical composition, mechanical properties.
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