The mining industry is a particularly tough environment for bearings applications, as bearings tend to wear easily, but by applying bearing coatings, such as the Durotect antiwear and reduced-friction protection coating, bearing life span is increased while wear downtime and damage on machinery can be redu-ced, says bearing distributor Bearings 2000.
“Coatings for bearings are designed to prevent or reduce fretting corrosion, wear, friction, slippage and electrical currents passing through bearings used in traction motors, gearboxes and wheel sets,” says Bearings 2000 director Nick Stamatiadis.
Bearings 2000 stock the Corrotect, Durotect, Triondur and Insutect range of rolling bearings-manufacturer Schaeffler’s branded coatings for various applications across industry.
He adds that the Schaeffler bearing coatings are designed to offer high-performance capacity and a long operating life. The characteristics of the components can be expanded using suitable coating systems, thereby offering the customer additional advantages for a specific application.
“By reducing friction, the coatings contribute to energy effi-ciency in the form of reduced energy consumption. These coatings can be applied to the surface of the bearing using a wide variety of methods. In many cases, however, it is sufficient to coat only one of the components in rolling contact or only a part of the component/s in rolling contact,” he explains.
“The Durotect antiwear and reduced-friction protection range can be applied to several local industries, including those of wind turbines, railway drives, rail vehicles, paper and pulp, cement mixers, shaker screens, traction motors for locomotives, clutch bearings, aerospace applications and cement mills,” highlights Stamatiadis.
The Durotect antiwear and reduced-friction protection coating is applied to prevent premature wear of rolling elements in traction motor bearings and axle box bearings.
The Durotect B-mixed iron oxide coating improves the running-in behaviour of bearings and supports deep-groove ball bearings in traction motors under poor lubrication conditions, says the company.
Meanwhile, the company’s zinc phosphate-based Durotect Z coating is used as an anticorrosion protection for axle box bearings, as it reduces fretting corrosion in the bearing seats and friction in the sliding fit. Further variants include Durotect M manganese phosphate coating for improved sliding and running-in behaviour and Durotect NP nickel-phosphorous coating for antiwear and anticorrosion protection.
Bearings 2000 began promoting the bearings coatings in mining operations by identifying and highlighting the benefits of each coating for each application, as well as the way in which each coating functions. “We then provide a sample for the end-user to fit and test the performance of the coating, compared with the performance of a standard coated bearing, whereafter the user can decide if the extra performance and elimination of risk outweighs the extra cost of the bearing,” he points out.
The company mentions that its Triondur tribomechanical stress-protection coating is developed specifically for rolling-bearing applications, as the Triondur coatings offer a high level of protection against abrasive and adhesive wear while reducing friction, as these coatings are ideally suited for use in traction motors.
This range of bearing coatings is suitable for use not only in the mining industry but also in various other industries that use bearings in their operations, as they can benefit from some of the coatings that are available in the Schaeffler range.
“Where there is a risk of slippage, owing to light loads, Triondur C – a carbon-based adamantine coating system – reduces dry friction against steel by up to 80%. Even if only one friction surface is coated, the operating life of the entire system will increase significantly. As a result of its highly ductile structure, Triondur C can withstand high contact pressures, making it a value-added product for the paper and printing industry, in addition to hydraulic motors, engine components and aircraft engines,” states Stamatiadis.
Industrial, automotive and agricultural industries can benefit from the Corrotect anticorrosion protection coatings, comprising the Corrotect zinc/iron alloy and the Corrotect zinc/nickel alloy (ZN), which are the preferred choice in highly corrosive applications. Axle box bearings in trains and passenger vehicles are particularly susceptible to corrosion, owing to environmental influences such as temperature fluctuations and humidity. Salt spray tests have shown that Corrotect ZN, in particular, offers up to 720 hours of protection against the formation of red rust.
Also, the current Insutect insulation is available either as an insulation coating or as ceramic rolling elements for the prevention of roller-bearing damage caused by electrical current. Stamatiadis notes that the selection of the most effective Insutect system depends entirely on the application in question.
“In the past, only bearings in large direct current motors or alternating current motors were particularly exposed to the dangers of electrical current. Currently, the potential hazards for bearings and the entire drivetrain in modern electric motors are growing because of the increase in the use of frequency converters. As a result, Insutect can be used in numerous applications today, which include traction motors, axle box bearing supports and generator bearings,” he concludes.