Stainless steel is a highly durable material that resists moisture and media corrosion. As a result, it’s an ideal choice for bearings that withstand high temperatures.
More resistant to corrosion
Compared to chrome steel, which is more often used, stainless steel is more corrosion-resistant. Its carbon content is relatively high, and its alloys can reach hardness levels of Rc58. However, stainless steel roller bearings have a lower load capacity than chrome steel bearings. In addition, a stainless steel bearing is more expensive than a chrome steel bearing.
The cost of stainless steel is higher than other metals, but it offers several significant advantages in specific situations. For example, unlike plain steel and chrome, stainless steel is less likely to corrode, which is especially useful for clean-room and food-grade applications. It also offers a long operating life and low noise levels.
As with other steels, the underlying material is what is essential. While steel is primarily composed of iron, carbon, and chromium, steel alloys add other elements. For example, chrome-molybdenum steel is made from iron, carbon, chromium, and molybdenum. Stainless steel is made from an alloy of iron, chromium, and nickel that resists corrosion.
Lower hardness than 52100 chrome steel
The hardness of a stainless steel roller bearing is considerably lower than that of a 52100 chrome steel counterpart. This difference can be attributed to the lower carbon content of the former and the increased hardness of the latter. Although the hardness of stainless steel is lower, it is still sufficient for most bearing applications.
Hardness is an important factor when evaluating the material for a roller bearing. In an approach, hardness represents the ability of the metal to resist fracture. This value is often provided as a percentage, with reference steel set at 100%. Then, the other steels are given a share of this value. Stainless steel, for example, has a lower hardness than 52100 chrome steel, which makes it ideal for machining purposes.
Although Chrome steel has a higher hardness than stainless steel, it is not as corrosion-resistant as stainless steel. The hardness of a stainless steel roller bearing is about 40% lower than that of a chrome steel roller bearing. However, it is also more resistant to wear than 52100 chrome steel. If you need to buy a bearing made of this material, you should always use a rust inhibitor.
More expensive than all-ceramic bearings
Stainless steel roller bearings are more expensive than all-ceramic approaches, but they have several advantages. They are non-magnetic and do not require lubrication. Standard steel bearings are prone to corrosion if exposed to strong acids and alkalis. The rusting can create particulate contamination, which is problematic. Unlike traditional steel, ceramic bearings do not produce harmful by-products and are, therefore, more environmentally friendly.
The high cost of ceramic bearings is mainly because manufacturing them requires massive energy. This energy is needed to reach the temperature required for sintering. Therefore, it is expensive, especially when manufacturing precision bearings. Additionally, ceramics are very sensitive to impurities, which can cause premature failure. For these reasons, choosing higher-quality paths is essential to avoid such problems.
The softer material of ceramic balls reduces the noise of the bearing and increases its service life. Ceramics also have a lower coefficient of friction than steel, which improves the ball’s surface stability and extends the bearing’s life. Despite these advantages, ceramic bearings are more expensive than steel and must be cleaned after a couple of work hours.
Suited for use in saline environments
Saline environments, like marine environments, pose many challenges for bearings. In addition to rusting due to water, they can also be attacked by various chemicals. For example, approaches used in food processing plants are exposed to daily high-pressure washdowns that are comprised of water and sanitizing agents. In addition, irrigation systems expose bearings to water containing fertilizer and sediment. Automated paint lines are also subject to conveying equipment to varying chemicals during the cleaning process. Even the paint itself can pose a problem for the bearings.
Thankfully, there are several techniques to lessen how these factors affect bearings. For example, specific custom bearings can be manufactured with integral seals to prevent lubricant leakage from critical surfaces. Alternatively, external seals can be made of either Viton or Teflon, which offer superior chemical resistance. Additionally, the design of the seal can make a significant difference. Double-lip seals, for example, can add additional protection without adding torque.
Another important consideration is the corrosion resistance of the bearing ring. Some materials used in bearing ring construction are prone to oxidation and rust. AISI 440C stainless steel is the most common, but specific applications require more corrosion-resistant alloys.