Standard alloy steels rely mostly on chromium carbide formation to impart more abrasion resistance. These carbide particles are microscopic in size, and constitute from less than 5% to over 20% of the total volume of the microstructure of the steel. Chromium carbides are about 65/70 HRC, molybdenum and tungsten carbides are about 75 HRC. Our thermal spray coating of XC1000 contains 88-90% by weight (80% by volume) of hard tungsten carbide. This hard, dense high volume percentage carbide layer at the point of wear provides the ultimate abrasive wear resistance possible. Harder carbides exist but compared to tungsten carbides none can be applied in a thick enough layer or with sufficient bond strength to offer any substantial value of the life of a feedscrew.
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 .005″ (.125 mm overall) of wear after 14 months of operation. This is a ten-fold improvement compared to the previous alloy