Over 35 Years of Providing Metallurgical Analysis

Scanning Electron Microscopy

The scanning electron microscope (SEM) uses a convergent beam of high-energy electrons to generate different signals from the surface of the sample. The signals which were derived from the sample interaction reveal information about the sample including morphology, chemical composition, and crystalline structure of the sample. The data is collected over a selected area of the sample surface, and a 2-dimensional image is generated that displays spatial variations in these properties. Using this data, 3-dimensionals images can also be produced. Areas of a few millimeters to several microns can be imaged using the conventional SEM. The magnification can range from 15x-50,000x. The SEM accompanied by energy dispersive spectroscopy (EDS) is capable of performing elemental analysis on selected locations of the samples. An accelerated electron beam is decelerated when it interacts with the solid sample. Several signals including secondary electrons (SE), backscattered electrons (BSE) and X-rays (photons) are produced. X-rays are used for elemental analysis. SE and BSE are commonly used for imaging samples. Secondary electrons are most valuable for showing morphology and topography on samples and backscattered electrons are most valuable for illustrating contrasts in composition in multiphase samples and expediting the elemental analysis. BSEs have higher energies which penetrate deeper into the sample than the secondary electrons. X-ray generation is produced by inelastic collisions of the incident electrons with electrons in discrete shells of atoms in the sample. As the excited electrons return to lower energy states, they yield X-rays that are of a fixed wavelength. Thus, characteristic X-rays are produced for each element in a mineral that is "excited" by the electron beam. SEM analysis is considered to be non-destructive; that is, x-rays generated by electron interactions do not lead to destruction of the sample; the sample can be reused. 

Macroscopic Photography
DNFM utilizes powerful digital cameras to capture the as received condition of samples, cross sectional areas, and macroscopic surface features. 
Analyzing the microscopic surface features of fracture faces can reveal important information regarding a component’s failure mode and stress state at the time of failure. Digital, light and electron microscopes are used to provide an accurate description of these surface features. Often samples are covered with deposits. These deposits are cleaned in an ultrasonic bath of diluted hydrochloric acid with corrosion inhibitor. The fracture morphology is typically captured with a high-resolution digital camera and scanning electron microscope (SEM). Our team specializes in interpreting microscopic surface images to provide root causes and recommendations to improve product performance. 

For more information email us at contact@davidnfrench.com or speak with us directly at 502-955-9847.