Most large diameter feedscrews have chrome plating surface treatment to the screw core. On a new screw this is a smooth surface that resists material build up. Eventually, with resins that are prone to sticking on the screw surface, a feedscrew must be removed for cleaning. Even careful handling of chrome plating will leave small scratches on the surface. These areas then foul more rapidly and the screw must again be removed and cleaned. XC1000 is 5-10 points harder on the Rockwell scale them chrome plate and will not scratch during cleaning. Our super surface finish .1 Ra µm reduces COF and ensures a long time between cleaning episodes.
All plastics processing feedscrews suffer from adhesive wear. In fact, 95% of all plasticating feedscrews are repaired or replaced due to adhesive wear of the flight outside diameter. Incidental contact between the rotating screw and the stationary barrel results in eventual reduction in diameter of the screw. This leads to longer plasticating times (Inj Mold) or reduced throughput (Ext) and overall lower productivity of a screw/barrel system. Bi-metallic feedscrews are an attempt to counter this adhesive wear by weld application of a better wearing alloy material on the top of screw flights. Our XC1000 tungsten carbide has proven to offer as much as ten times more adhesive wear resistance than standard alloys in real world applications. An example – 4-1/2″ 24:1 extrusion feedscrew wearing .020″ (.5 mm overall) in 13 months. A layer of .020″ (.5 mm overall) of XC1000 on the screw flight had only .002″ (.125 mm overall) of wear after 14 months of operation. This is a ten-fold improvement compared to the previous alloy.
For the past 15 years, Extreme Coatings, Inc. has had tremendous success using thermal spray carbide coatings to significantly increase the life of the feed screws used in plastic injection molding and extrusion equipment. The same technology and expertise is now being used on downhole mud motor rotors for the oil and gas drilling industry.
For Extreme Coatings, the move was a natural one. The geometry and actions of mud rotors are very similar to those of feed screws, so existing technology and working methods were directly applicable.
Mud motors are a type of displacement pump used in drilling for gas and oil. The most expensive part to replace is the power section, consisting of a rotor and a stator. Historically, stainless steel rotors have been chrome plated. When the drilling fluid, or mud, is fouled, the chrome plating can rapidly wear away in places and build up in others. When that occurs, the incorrect fit can cause a loss of power to the drill and eventual motor failure. With increased exploration into corrosive environments such as shale formations, the demand for more corrosion- and wear-resistant coatings has grown.
Through new coating development like their CPR (Chrome Plating Replacement) coating and refined polishing techniques, Extreme Coatings is not only repairing the mud rotors, they are making them run better. Extreme Coatings strips away worn chrome plating and replace it with a more corrosion resistant high velocity oxy-fuel (HVOF) thermal spray coating. The tungsten carbide used in these coatings is harder than chrome, and the method of application and polishing results in a high finish that reduces friction. This can increase the life of a rotor by six to ten times.
This is a shout out about our carbide coatings for Halogen-free flame retardant applications. These are nasty corrosive materials that are growing in usage in the electronics industry. Processors that are used to equipment life of 24-30 months for PM tool steel are totally surprised when they change materials to a product with zero halogen in it. They can see their feedscrews reduced to broomsticks in a matter of 3-4 weeks!
The issue is corrosion AND abrasion at the same time. Corrosion resistant steels form an oxide layer that protects the surface from continuous corrosion. With an abradant (glass fiber) in the mix this oxide layer is constantly removed and the result is a loss of material at a rapid rate.
Our tungsten carbide coatings are inert and the finished coating layer hard and has very low porosity. Once a feedscrew is coated it will last at least as long as the original PM steel screws in this halogen free material. I will post a link here soon with a copy of an article from the German press about this problem.