Hardness
One of the key factors affecting stellite machining is hardness. The hardness of a material can be determined using various tests. Some of these include the Rockwell test, Barcelo test, durometer test, Brinell test and Mohs test. Hardness measures how resistant a material is to scratching or breaking. It depends on the bonds between minerals. Minerals are graded around the Mohs scale for assigning numerical values to this property.
Historically, the hardness of a mineral was measured by observing whether a sharp object could scratch it. However, this has since been replaced by more practical tests.
Metallurgists performed the first tests in Europe and the United States. Today, there are many types of indentation and abrasion tests. The Rockwell hardness test uses a specially dimensioned indenter to produce a specific impression shape. A light load is added to seat the indenter and eliminate any surface irregularities, followed by a major load of up to 40 kilograms, depending on the indenter used. The depth of the impression is then measured.
Corrosion Resistance
Stellite is a family of cobalt-base alloys that are completely nonmagnetic and corrosion-resistant. Several compositions are currently formulated to optimize combinations of wear resistance, corrosion resistance, or the ability to withstand extreme temperatures. The hardness of these alloys is largely due to the presence of chromium, carbon, and tungsten in the metal. These compounds are significant and contribute to the material’s high strength, flexibility, and toughness. These properties make these alloys excellent for machining. However, it is important to use the right tool and a proper cutting speed to avoid heat and chip thinning. Stellite 6 has excellent corrosion resistance and can maintain this property even at high temperatures. This is due to a hard carbide phase dispersed within the CoCr alloy matrix. This dispersion, along with the fact that Stellite 6 coatings do not melt, allows them to keep their properties during long exposure to high temperatures.
Abrasion Resistance
Abrasion resistance is the ability of a material to withstand wearing down or rubbing away by friction. This helps keep the material’s original structure and look intact. This is important in constructing floors, roads, or pavements, where abrasion can cause damage to materials. Concretes with greater compressive strength is more abrasion resistant than weaker ones. Several test methods can be used to measure abrasion resistance. One of the most simple is the falling sand test, which involves releasing standardized sand and determining the amount needed to wear down a coating. Abrasion resistance is an essential factor in a high-performance coating. This is because it can prevent wear and abrasion that will negatively impact the overall functionality of your product. It can also help reduce the cost of the application.
Heat Resistance
Stellite is a range of cobalt-chromium alloys designed for wear resistance and may also contain tungsten or molybdenum and a small but important amount of carbon. Elwood Haynes invented it in the early 1900s as a substitute for flatware that stained or required constant cleaning. Its heat resistance is excellent. Its low coefficient of friction allows it to be used in various situations where lubrication is not possible or is too costly.
As a result, it is used in diverse applications such as food-handling machinery, chemical equipment, and others where wear and corrosion resistance are required. It is also used in various industrial valves and fittings and in medical implants such as artificial hip joints and heart valves. Unlike many other heat-resistant superalloys, Stellite is nonmagnetic, anticorrosive and non-reactive to human body fluids, which makes it ideal for use in surgical tools and heart valves. However, it is not suitable for use in nuclear power plants because of the presence of gamma rays generated by the neutron flux in the reactor.
