Introduction
Non-Destructive Testing in the industry is used to evaluate the properties and characteristics of materials without permanently damaging or altering them. They are commonly used in industry to detect potential defects or anomalies in materials, including brittleness that can affect asset integrity .
Brittleness is a property indicating the susceptibility of a material to fracture or break under load or stress. Brittle materials have a tendency to fracture or crack easily, even under relatively low loads, while ductile materials can withstand much higher loads and stresses before fracturing.
Materials used in critical structures, such as aircraft, pressure vessels and pipelines in the oil and gas industry, bridges, or buildings, must have high strength and low brittleness to ensure safety and durability.
Factors Affecting Brittleness of Materials
There are several factors that can affect the brittleness of materials, among the most important are mentioned.
The microstructure of the material: This refers to the crystalline structure and the distribution of phases within the material. A poorly designed or defective microstructure can weaken the material and increase its brittleness.
Temperature: Some materials, such as steel, can become more brittle at low temperatures, as the iron atoms that make up the steel begin to move more slowly as the temperature decreases, reducing their ability to absorb energy and makes them more prone to fracture. As the temperature drops below room temperature, hardness and cadence resistance increase.
On the other hand, at high temperatures, embrittlement occurs due to the loss of strength of the steel. As the temperature rises, the iron atoms move faster, weakening the bonds between them and making the steel more prone to warping and fracturing.
In addition to temperature, the presence of a particular element and the incidence of another variable such as pressure, can cause it to combine with other elements within it, creating fragile structures,
An example of this is the attack by hydrogen at high temperatures (HTHA) in low alloy steels, where at certain temperatures and partial pressures of hydrogen, this element combines with carbon from the grain boundaries, forming methane whose pressure is increases with time making the structure of the material brittle.
Stress corrosion cracking results from the combined action of an applied tensile stress and a corrosive environment, both influences are necessary. SCC is a type of intergranular attack corrosion that occurs at grain boundaries under tensile stress. An example of this is hydrogen embrittlement, which is one of the many forms of stress corrosion cracking, hence the importance of continually performing the industrial maintenance .
In addition, manufacturing processes can also affect the brittleness of materials. If a material is subjected to an improper manufacturing process, such as incorrect temperature or cooling rate, this can affect its microstructure and increase its brittleness.
Non-destructive testing in industry: Determination of the brittleness of materials
There are several non-destructive testing methods in the industry that are used to detect the brittleness of materials. Some of the most common are:
Ultrasonic testing: Ultrasonic testing is one of the most widely used END methods for material characterization. The parameters of this test method are significantly affected by changes in the microstructural or mechanical properties of materials.
Some of the important metallurgical properties that have been correlated with ultrasonic testing parameters are grain size, inclusion content, elastic modulus, hardness, fracture toughness, yield strength, tensile strength, among others, and from the results of these parameters the condition of the material evaluated as brittle or ductile can be determined.
Induced Current Test: Non-destructive testing by Eddy Currents (ET) is basically based on the interaction of alternating magnetic fields with electrically conductive materials. The electrical conductivity of materials can be deduced from the ET test, making it a practical method for material characterization.
Residual stresses in a material, as well as its hardness, can be evaluated by applying the Eddy Current test and from there, estimating the brittle condition of the inspected component.
X-ray Test: Advanced techniques such as X-ray diffraction can be applied to determine the crystalline structure of a sample and hence its condition as ductile or brittle, this by determining lattice parameters and grain size.
Conclusion
Materials with a brittle condition can be present in industry, and this brittleness can have serious consequences. In general, ENDs are used to identify potential defects or weaknesses in materials that could affect their ability to meet your performance and safety requirements. By detecting and measuring the brittleness of a material, NDTs can help prevent potential failures and accidents.
Bibliographic references.
Ultrasonic materials characterization. L.Smith. https://www.sciencedirect.com/science/article/abs/pii/0308912687903713
Material Characterization by Electrical Conductivity Assessment Using Impedance Analysis. Guillermo Cosarinsky, Javier Favab, Marta Ruch, Adrián Bonomi. https://www.sciencedirect.com/science/article/pii/S2211812815000218
Application of X-ray Diffraction. https://qsstudy.com/application-x-ray-diffraction/
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