By Brian Dahmer | Director of Application Engineering • SKF
Many materials in the rolling elements of bearings — both linear and rotary — have been used for over a century. But slowly, new materials are finding their way into industrial applications. Increasingly, new materials are being developed for rotary bearings used in very challenging applications, such as those found in aerospace and machine tools. Given the high reliability required in these applications (plus the challenging conditions these bearings encounter) more exotic and higher-performing materials are often needed. Eventually, these materials trickle down into more standard industrial applications.
For example, aerospace bearing steels are now used in a range of challenging industrial applications, such as extreme temperature, high rotational speed, demanding loads, and exceptionally challenging environmental conditions. As these materials prove themselves in the industrial world, they percolate to new and different applications. Examples of the transition from aerospace or the machine tool industry to industrial include various types of M50 tool steel and special high nitrogen stainless steel. Powder metallurgy steels are also being utilized and show excellent performance in tough conditions.
Often existing materials can offer improved performance by changing the heat treatment used for those materials. In computer-controlled heat treatment processes, the resultant heat-treated steel can be optimized to offer improvements, such as high wear resistance. Additional surface treatments such as nitriding can also be added to a hardened bearing to further improve performance in tough, contaminated environments. Adding a surface conversion layer, such as black oxide, improves initial wear-in conditions, leading to longer and more consistent bearing fatigue life.
Another technology that has grown in adoption and acceptance in industrial applications is hybrid bearings using ceramic rolling elements and steel rings. Originally used in machine-tool spindles, hybrid bearings have spread into numerous industrial applications where this configuration can improve bearing performance … though finding bearing quality ceramic balls and rollers has become more challenging of late. Not all silicon nitride materials are suitable for very demanding applications. The materials used in proven solutions are in high demand but scarce. Bearing manufacturers are challenged to find available silicon-nitride materials that function well in challenging rolling bearing applications. New ceramic formulations are being tested and show promise. If they prove to be successful, the supply of available materials will increase, allowing hybrid technology to be used in even more applications.
This article was published in the 2023 Design World Trends issue. Read other articles in the Design World Trends series at designworldonline.com/trends.