For more than 65 years The Lund Industrial Group has provided innovative solutions to challenging cutting, wear, and corrosion related problems.

Capabilities -> Technical Information

Tungsten Carbide Spray-and-Fuse

The spray-and-fuse process is a two-step process in which powdered coating ma­terial is deposited by using either a combustion gun or plasma spray gun, and subse­quently fused using either a heating torch or a furnace. The coatings are usually made of nickel or cobalt self-fluxing alloys to which hard particles, such as tungsten car­bide, may be added for increased wear re­sistance. Coatings ranging from 0.020 to 0.080 in. thick can be made by building up several layers at a rate of 0.005 to 0.030 in. per pass. Typical deposition rates are 9 to 12 lb/hr.

Most workpiece substrate metals can be hardfaced using the spray-and-fuse process without special precautions, while others require special pre-heating or cooling procedures to prevent cracking of the hardfacing. Most plain carbon, manganese, molyb­denum, chromium, chromium-vanadium, and nickel-chromium-molybdenum steels can be hardfaced by the spray-and-fuse process without special precautions, provided the carbon content is below approximately 0.25%. When the carbon content of-the steel is above 0.25% the workpiece requires a 500 to 700°F of preheat prior to fusing the sprayed coating and slow cooling after fusion.

Irons (such as gray cast, meehanite, malleable, ingot, and wrought) and nonferrous metals and alloys (such as copper, nickel, Monel 400, Inconel 600, Nichrome, and most high­ temperature alloys) are also amenable to hardfacing by the spray-and-fuse process without special precautions.

There are many formulations of tungsten carbide powders, and Lund engineers rely on many years of experience to select the optimal formula for a specific application.

 

WEAR-TUFF Abrasion Resistant Coating

The WEAR-TUFF process permits Lund to coat metal parts with a low cost, mass produced, smooth wear coating that is particularly effective at resisting abrasion. The material consists of alloy powders, carbides, and fluxes. By varying the amount of viscosity control agents,  WEAR-TUFF can be applied either as a slurry or sprayed on.  The coated parts are dried and then sintered in a controlled atmosphere furnace. This fuses the material to the substrate with a true metallic bond. If desired, the parts can then be heat treated to the desired mechanical properties.

WEAR-TUFF can be applied at virtually any thickness. However, the optimal range for ground engaging applications is 0.025 to 0.040 in. Hardness typically is in the range of 60 to 65 Rockwell C.

WEAR-TUFF can be applied to steel, iron or other metal substrates.

 

BrazeCoat Ultra-High Density Carbide Coating

The BrazeCoat process can be applied in two ways. The BrazeCoat-M Process results in a thicker wear resistant coating, while the BrazeCoat-S process results in a thin, smooth coating. Both are processed in Lund’s hydrogen atmosphere furnace and both result in coatings of extremely high tungsten carbide content by weight.

With the BrazeCoat-M Process, flexible mats, consisting of carbide powders and filler metal powders (e.g. NiCrBSi), bonded by a polymer binder are cut into the appropriate sha­pe and placed onto the substrate. After preparation the assembly is heat trea­ted in a furnace process at approx. 1100 °C under the protective hydrogen atmosphere. The carbide layer is infiltrated by the molten filler metal and in the same operation brazed to the substrate. In the BrazeCoat-M process the thickness of the resulting layers can be adjusted between 0.7 mm (0.028 in.) and 3 mm (0.12 in.) or even more. The final layer conforms to the contour of the part.

Typical applications for BrazeCoat M-layers can be found where heavy abrasive wear or even a combination of abrasive and corrosive wear appears. Slurry pump housings, mixer blades and extruder parts, all coated by the BrazeCoat-M process, have resulted in signifi­cantly longer component lifetime under actual service conditions.

With the BrazeCoat-S Process the surfaces of components are protected against severe wear by spray depositing a carbide/hard facing alloy suspension, which is then heat treated in the hydrogen atmosphere fur­nace. The thickness of the resulting layers can be adjusted between 0.05 mm (0.002 in.) and 0.5 mm (0.02 in.).

The coatings are well bonded and show a porosity of less than 1%. The surface as coated is very smooth, and for most applications final ma­chining is not necessary. Due to the high car­bide content of the coating layer, hardness values of over 65 HRC are obtained. Wear tests, under laboratory conditions as with components under service conditions in the field, showed improved resistance against abrasive wear over nitrided, borided or ther­mally sprayed layers.

The BrazeCoat-S Process has been applied successfully to protect fan blower disks, hou­sings and mill rotors, hydraulic cylinders or plungers and piston rods in hydraulic and pneumatic application where a severe wear attack is combined with the requirement for narrow tolerances.

Innobraze GmbH


Laser Clad Hard Facing

Lund can aslo provide hard facing fused utilizing a laser. The advantages of the process are several. The laser imparts heat in a very specific zone, so that while a true metallic bond is created, the heat effects on the base material from the fusing process are minimized. Moreover, the hard facing can be applied in very precise areas and patterns.

 

High Velocity Oxygen Fuel Spray

The High Velocity Oxygen Fuel (HVOF) process relies on an oxygen-fuel mixture consisting of oxygen along with propylene, propane, or hydrogen to produce a high quality wear resistant coating.

Powdered coating mixture is passed through the HVOF gun. The fuel gasses are mixed and injected into the front portion of the gun. The thoroughly mixed gasses are ejected from the gun nozzle and ignited externally. The ignited gases form a circular flame configuration surrounding the powdered material as it flows though the gun. Combustion temperatures are between 5000 and 6000 °F, depending on fuel gas. The circular flame shapes the powder stream to provide uniform heating, melting, and acceleration. Pre-selected oxygen, fuel and air values are specified for each powder material to optimize dwell time in the flame.

The key characteristic of the HVOF process is the extremely high kinetic energy that is produced and transferred between the HVOF gun and target substrate. Typical velocities are between 5000 and 7200 fps. With both thermal and kinetic energy, the high velocity particles are physically embedded into the substrate to form a coating with the following attributes:

  • High density
  • High physical bond strength
  • Low porosity
  • Low thermal input to the substrate
  • Essentially stress free
  • Relatively thick deposits possible

Plasma Transfer Arc Spray

Hard facing by Plasma Transfer Arc (PTA) relies on a gas-shielded arc created between a non-consumable tungsten electrode and the workpiece as the primary heat source. The plasma is formed by ionizing the gas flowing in a nozzle surrounding the electrode. The electrode usually is recessed into the nozzle, and the plasma gas generally emerges from a constricting orifice arrangement. The process can use bare rod or wire as a hard facing consumable, but more often pow­der is used. When powder is used, the process is referred to as the plasma transferred arc process.

The powder is directed from the torch into the arc ef­fluent, where it is melted and fusion welded to the workpiece. A direct current power supply connected between the tungsten electrode and the workpiece provides the energy for the transferred arc. The shielding gas is passed through a diffuser and forms a blanket in and around the arc zone.

Powder recoveries as high as 95%, with deposition rates up to 10 lb/h, are possible, depending on the size and shape of the part being hard faced.

Hard facing with the plasma transferred arc process has many advantages. Hard facing deposits can range in size from approximately 0.01 in. thick by 3/16 in. wide to approximately 1/4 in. thick by 1 1/2 in. wide by simply varying the welding cur­rent, powder-feed rate, oscillation and travel speed. The process is amenable to automation, which makes it well suited for high production involving a large number of parts.

 

Heat Treating

Along with material selection and wear resistant surface treatment, a third key to a long lasting cutting or wear component is its heat treatment. Depending on the application, Lund will utilize several types of heat treating, including selective zone hardening, through hardening, austempering and carburizing. Often, a combination of heat treatments is used to optimize the performance of the wear part.

In the case of a cutting part, selective edge hardening is often employed. In its "soft" state, the cutting part is essentially useless. In the heat treatment process, the cutting edge is heated to over 1500 °F. On subsequent cooling the steel undergoes a transformation to Martensite. This process produces a cutting edge that is very hard and that will retain its sharpness far longer than the untreated steel. The mounting body of the knife, however, is not affected by this treatment. Accordingly, it remains ductile and tough. It can bend under load without breaking or taking a permanent set.

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