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. 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. Stellite 21 is much less prone to cracking in our experience when we can talk the customer into it over 6 we do it every time. Cracking has been observed in valve components at the stellitesteel. Stellite 6b is supplied in the solution treated condition to ams 5894 and its wear resistant.
Not familiar with your rod so i dont know the hardness rating there are many factors involved when hard facing according to the nature of the part but as a general rule its not good practice in the type of things i do to use 600 or over hardness without buttering the base metal with say 400 first this is when cracking seems to be a problem if your stuck in the. However, limited reports can be found to study the thermal fatigue cracking property of a stellite 6 coating modified with both titanium and nickel. The material is also resistant to erosion and most. Plasma transferred arc welding of stellite 6 alloy on stainless steel for wear resistance. There are a large number of stellite alloys composed of various amounts of cobalt, nickel, iron, aluminium, boron, carbon, chromium, manganese, molybdenum. Most of the time, this material is stellite, a cobaltbase. See each listing for international shipping options and costs. Laser assisted deposition of graded overlay of stellite 6 on. Laser assisted deposition of graded overlay of stellite 6. The chemical composition of stellite 6 is given in table 3. The initial state of stellite6 surface before experiments was. Number of bids and bid amounts may be slightly out of date. Stellite is a nonmagnetic alloy which contains a variety of different metal components with the main elements being cobalt and chromium. Argon gas was used as the shielding gas as well as the medium for generation of plasma in pta process.
Dry sliding wear map for stellite 6 against a wcco 9010 disc 12 49 figure 214. Cocrw meets or exceeds ams 5894, pwa 1196, mcs 1012 and uns r30016. Stellite 6 hard facing onto monel welding, bonding. Stellite 6 is a well know overlay in the pump and valve industry. Product forms ultimet alloy is available in most common wrought product forms. 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. Two layers of stellite 6 were coated for a maximum thickness of 6 mm or higher. 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. Stellite definition of stellite by the free dictionary.
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. The micrographs of the stellite6 on surface and cross section have been obtained after polishing till diamond grade 1 m. This article presents development of graded overlay of stellite 6 on aisi 304 stainless steel substrate using 2. 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. Tensile strength is 758 mpa, yield stress is 655 mpa, youngs. 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. Table 1 gives the chemical composition and some physical properties of stellite 6 alloy. A comparative study for wear resistant of stellite 6. Recharge by welding a carbon steel valve with inconel625 825 overlay, cladding.
This type of polishing was used only for sem observation of stellite6 deposit before wear corrosion experiments. A strategy is given to improve the ductility and thermal fatigue cracking feature of stellite 6 coating by adding ti and ni. Stellite is a family of completely nonmagnetic and corrosionresistant cobalt alloys of various compositions that have been optimised for different uses. Stellite 6b is a cobaltbased steel alloy that maintains a wide range of material benefits for industrial applications throughout the world. If your valve orifice is narrow and the valve is throttled in service quite often, then stellite 6 would give a better long. 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. Then we have to get 5mm thickness of cocra alloy overlay. Impact wear resistance of stellite 6 hardfaced valve seats. How to control check cracking and use to your advantage. It may also contain tungsten or molybdenum and a small but important amount ofcarbon. Stellite failure on a p91 hp valve failure investigation. 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. Laser cladding, hvof, plasma spraying, stellite 6 coating, friction and wear, nickel alloy. The brittle nature of the metal carbides leads to check cracking, and as multiple layers are applied, stress continues to build, concentrating at the root of the check cracks, until separation or spalling occurs between the parent metal or buffer and the hardfacing deposit.
Erosion test curves of stellite alloys 7 51 figure 215. A cobaltbased alloy, stellite 6, was deposited on the seat face of control valves using a coaxial laser cladding process. Because of the presence of the carbide network, the overlay is somewhat prone to cracking. Hard facing hf and corrosionresistancealloy cra with hot wire, materials.
I have seen many valves refurbished in the field with stellite 21 being replaced with stellite 6. The issue of whether hardfacing adversely affects the properties of duplex stainlesssteel base materials depends on several factors. However, when we finished the second layer and let it cool gradually wrapping the cone with. Stellite 6b cobalt alloy steel cobaltchromium alloy. Aug 15, 20 the carbides present in the cocrwbased stellite alloys are of chromiumrich m 7 c 3 type.
These hardfacing layers are applied as an overlay onto a steel substrate, such as crmo steel i. Stellite 6 overlay on the disk contact surfaces of a dual plate check valve photo courtesy of crane stockham valve table 1. Microstructure evolution and failure behavior of stellite. Overlay repair of dissimilar metal alloy 82182 welds with. Fisrtly, we had a 3mm thickness of 309mol overlay with fcaw. Stellite 6 welds pretty clean unless it gets oxidized and then the puddle gets sluggish. Also we can apply other materials such as stellite 6 or 12 or nickel ni 100%. Can duplex stainless steels be hardfaced without adversely affecting the base material properties. 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. Hpa cobalt 6b is a wear resistant alloy used for stems, balls, rails and bushings. The prequlualified procedure has worked well in the past however, current production tests are showing intergranular cracking in the monel inconel haz, but only after application of the stellite.
Sprayfuse coatings, also referred to as selffluxing overlay coatings, are first applied to the component surface using a flame spraying process and then subsequently. Implementation of stainless steel buffer layer for reducing crack. Developing the ductility and thermal fatigue cracking property of. We took the method of smaw with the stick electrode of stellite 6. For comparison with conventional hardfacing techniques, a plasma transferred arc pta method was chosen for parallel experiments in this study. The microstructure evolution, elements diffusion and fracture behavior of the stellite 6 weld overlay, deposited on 10cr9mo1vnbn f91 steel by the tungsten inert gas tig cladding process, were. I have never heard of using stellite 21 as an interlayer before welding stellite 6. Stellite 6 welding rods hai stellite 6 rod is cobalt base rod. This alloy also has higher hot hardness and resists galling like all stellite alloys when mated with another stellite alloy.
The brittle nature of the metal carbides leads to checkcracking, and as multiple layers are applied, stress continues to build, concentrating at the root of the check cracks, until separation or spalling occurs between the parent metal or buffer and the hardfacing deposit. However, when we finished the second layer and let it cool gradually wrapping the cone with insulate material, we could see some crackings on the second. Cobalt alloy 6b stellite 6b ams 5894 aircraft materials. Aug 12, 2011 the alloy stellite 6 has less tendency to crack than for example stellite 12, but only when multilayer technique is used. For small, simple parts, cracking is not a usually a problem. Not familiar with your rod so i dont know the hardness rating there are many factors involved when hard facing according to the nature of the part but as a general rule its not good practice in the type of things i do to use 600 or over hardness without buttering the base metal with say 400 first this is when cracking seems to be a problem if your stuck in the field with only. The microstructure of stellite 6 contains hard m 7 c. Alternate stellite process material selection and properties. Thermal fatigue cracking is one of the main lifelimiting factors for the brake discs of trains. The laserclad layers, which consisted of refined solidification structures, were characterized by. Pdf delamination failures of stellite hardfacing in power. 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. Pdf delamination failures of stellite hardfacing in power plants.
Developing the ductility and thermal fatigue cracking. Hardfacing a standard term for a wearresistant weld overlay is commonly used for seat and guide surfaces on valve trim of all. What is the best gas to use when doing a stellite overlay on 316ss. Hardfacing a standard term for a wearresistant weld overlay is.
Hightemperature hardness and wear resistance of stellite alloys. Recharge by welding a carbon steel valve with inconel625 825overlay, cladding. 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. Pta hardfacing of stellite 6 on stainless steel has been carried out in plasma transferred arc pta welding machine since it is a semiautomated process. The alloy stellite 6 has less tendency to crack than for example stellite 12, but only when multilayer technique is used. Hardfacing is a metalworking process where harder material is applied to.
A metal source, llc stellite alloysstellite alloys. 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. It is easily deposited by a number of methods but you do have to be careful about contamination from sulphur or phosphorus. Ti addition made the m 23 c 6 eutectic carbide change to the tic carbide. With ultimet alloy, cracking of the overlay is not a consideration, and multiple layers may be applied, with little or no preheat. Stellite 21 will work harden to develop full hardness. These hardfacing layers are applied as an overlay onto a steel substrate. So it is possible to apply the material without cracks but in cases where the hard facing also is used for corrosion resistance or for a perfect. Typical hardfacing materials deposited by thermal spraying include cermets such as wcco and aluminabased ceramics. 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. Pdf delamination failures of stellite hardfacing in. 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.
The modified stellite 6 coating with improved performance may play an important role in prolonging the service life of brake discs. Delamination failures of stellite hardfacing in power plants. A comparative study for wear resistant of stellite 6 coatings. Today, the hardening of sealing surfaces is performed by welding a material harder than the valve body material. Some of the main advantages that stellite 6b cobalt chromium alloy provides includes. Depending on how long the weld is and how its layed out, some cracking is usually inevitable with stellite 6 its normal. Since the thickness is 5mm, we have to do 2 layers.
Cracking resistance of stellite 6 clad austenitic stainless steel components can be greatly enhanced by providing smooth composition gradient across substrateclad interface. The different process steps are coupled in order to transfer the residual conditions from preceding processes to the ones following. 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. Plasma transferred arc welding of stellite 6 alloy on. It may also contain tungsten or molybdenum and a small but important amount of carbon composition.
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. Author links open overlay panelyingwuyanliu huichen yongchenhongyuli xinyucao. A hard carbide phase in the cocr alloy matrix makes this material highly resistant to corrosion and galling. 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.
These coatings are applied to a thickness of about 0. Most crackings are perpendicular to the welding seam. Hightemperature hardness and wear resistance of stellite. Influence of yttrium additive on wear behavior of stellite 6 at elevated temperatures 25 54. 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. Find great deals on ebay for stellite and stellite tool bit. Stellite alloys chemical composition, mechanical properties.
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. In single layer applications you probably will have small cracks. The hot hardness of stellite 6 weld overlays drops off sharply as iron content increases up to 10%fe, but at higher fe contents the drop is insignificant up to 20%fe. Cracking has been observed in valve components at the stellitesteel interface and in the weld. Stellite alloy is a range of cobaltchromium alloys designed for wear resistance.
Microstructure evolution and failure behavior of stellite 6. It is very easy to apply as an overlay, compared with the traditional cobaltbase wear alloys. Stellite 21 is a little softer hard facing alloy compared to stellite 6 and may stand the same duties same steam service without erosion corrosion of disc or failure of stems and comparatively easier than stellite 6. 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. Co base stellite 6 hardfacing was deposited onto the stellite 21. I am currently applying stellite 6 onto cast monel 400 astm a494m351 using pta and normally use an inconel 625 buttering layer. Stellite 6 overlay on the disk contact surfaces of a dual plate check valve.
468 411 886 514 1100 1442 702 599 41 731 1546 1086 784 200 891 1272 1330 808 1166 898 989 182 1163 619 689 159 1182 363 1011 111 217 925 1059 726 499 385 1331 1291 1351 316 1265 1054