Kirko provides carbide coating on our feed screws and other high wear components; we offer a full line of abrasion and corrosion resistant coating products to meet the needs of today’s most demanding abrasive and corrosive compounds.

The Process

Very high velocity thermal spray technology uses extremely high temperatures above 6000 F, to heat ultra-fine particles of the coating material, typically less then 0.0003" in diameter. The molten particles are applied to the feed screw at very high velocities of approximately 2,500 feet per second. Upon impact the particles flatten, solidify, and form an interlocking bond to themselves and the screw substrate. The kinetic energy released by impingement upon the substrate contributes additional heat and promotes bonding. The coating is built up to the specified thickness while the screw is rotated and passed in front of the gun. The sound level of the spray gun is the same as that of a jet engine during take off.

The Coating

Plasti-Co’s "PCS" brand carbide coatings provides abrasion resistant characteristics unmatched by any of the conventional hard-surfacing alloys and treatments offered. It provides a crack free coating of 80 to 90% sub-micron sized Tungsten Carbide, with an overall hardness of 68 to 71 Rockwell. The common flight hard-surfacing alloys only have a 53 to 58 Rockwell.

Thickness & Finish

Thickness is determined by application and feed screw size. The coating can be applied in thickness of .005" to .015" per side, providing .010" to .030" of total wear protection.

We offer a variety of root and flight side surface finishes ranging from +/-140 RMS to our 16-32 RMS finish, which rivals chrome plating in appearance. Carbide coated screws that are not polished after the coating is applied can in some cases, cause feed problems and can take much longer to purge or change materials.

Beneficial characteristics of our coatings include:

• Excellent wear resistance.
• Can be stripped when worn.
• Corrosion resistance.
• Low coefficient of friction when high polished.

Rebuilding PCS coated screws: When worn, our coatings can be stripped and the screw recoated.

Hard-Surfacing

Hard surfacing is a process of protecting metal parts from wear by binding a wear-resistant alloy to the ferrous or alloy base metal. Mostly used on flight tops, it is applied for a final thickness of around 1/16" (.062"). As the wear progresses, the wear resistance will not decrease until the hard surfacing is worn off.

 Hard-Surfacing a Feed Screw Mixer.

 Flights with Hard Surfacing.

The two most widely known brands of hard surfacing are Colmonoy and Stellite. Each supplier manufactures a number of formulations that are well suited for feed screw use. Colmonoy’s products are nickel based and Stellite uses a cobalt base. These products are specially formulated alloys that contain both wear and corrosion resistant materials like Chromium, Carbon, Nickel, Cobalt, Tungsten and Boron. They range in hardness from 37 to 64 Rockwell.

Mixing Feed Screws Most feed screw manufactures offer a "ONE SIZE FITS ALL" mixing screw or a section in their general purpose screw, without even knowing what the customer's problems or needs are. They often charge a very high premium for their screw which more often then not, does not solve the problem and may even make it worse. At Kirko each customer needs are evaluated. A new screw is designed or a change to the customers screw design is proposed to overcome a problem or improve their process. Our  P-3000 is a very versatile mixer with 18 parameters that can be changed to more effectively fit a customers needs. Most mixing sections use sample back pressure or flow restriction to cause mixing, which is no more effective then turning up the back pressure on the machine. These types of mixers over shear the material and can burn or degrade the plastic, which greatly reduces the machines output and are difficult to purge. 1st-STAGE MINIMAL P-3000 MIXER More important than the mixing section itself is the profile of the screw, its section lengths and flight depths. A screw cut too deep in the feed section or with a transition section that is too short can render a screw with the most elaborate mixer useless. 2nd-STAGE P-3000 MIXER The P-3000 can be used where minimal mixing is needed or with very shear sensitive material like PVC, some vinyl and rubbers. It may be used on short L/D ratio screws with a higher compression ratio for mixing standards thermoplastics. 3rd-STAGE P-3000 MIXER VERY AGGRESSIVE P-3000 MIXER The P-3000 concept has worked well in a very wide variety of applications. Compounding companies using it to mix as much as 60% talc powder into P.P. for a more homogeneous parison flow on a high production blow molder. But by far the most common usage is by injection molders for color mixing.  Following are the reasons why: Lower percentage of color concentrate required. Improved overall dispersion and homogeneous melt. Low shear with no "dead ends". Higher outputs or faster screw recovery in most applications. Easy purging. Flexibility to run a very wide variety of materials with one screw. Higher percentage of regrind can be used. Efficient and cost effective.

Specialty Feed Screws We can build screws with many types of flight designs for different applications. Plasti-Co can improve your screws output, make your process more profitable and improving the mixing action for color or other additives. The right screw for your needs can improve overall part quality and reduce scrap rates.