Dye Penetrant and Fluorescent Powder Testing
When your quality standard requires a surface finish free from tiny cracks, pores or other surface glitches that are hard to detect by the human eye, dye penetrant testing is used for both ferrous and nonferrous materials. The part is cleaned and a colored dye solution is applied to the surface of the part. The dye is suspended in penetrating oil and will freely flow into these surface imperfections. When our special developer is applied, the defects are clearly indicated.
A similar method suspends fluorescent powder in penetrating oil. This brightly colored film covers the parts and the penetrant finds its way into any defects.
Then the casting is dusted with drying powder and the fluorescent solution is drawn from the defect. Then a visual inspection in an ultraviolet light environment will easily show the defects as they will glow.
Generally, dye-penetrant testing techniques will identify defects on the surface of the casting and will not detect internal porosity or shrinkage that is not open to the surface. But these methods can detect rounded indications for porosity or gas on the casting surface. These two methods are less expensive than radiographic testing.
How we prove your products meet standards?
We start by understanding your quality standards. We comply with ASTM standards and we are NADCAP accredited for Flourescent Penetrant, Magnetic Particle and Radiography Film. The standards that your parts need to meet will determine the process that we use. Below are the processess that we specialize in perfoming.
Magnetic Particle Inspection
Magnetic particle Inspection (MPI) detects surface and slightly subsurface discontinuities in ferromagnetic materials such as iron, nickel, cobalt, and some of their alloys. A high-amperage, low-voltage current is passed through the casting, which establishes a magnetic field. Magnetic flux is introduced to the part. Since cracks and defects have different magnetic properties than those of the surrounding material, their presence causes distortion by interrupting the magnetic field, thereby indicating the shape and position of the crack or void.
The piece can be magnetized by direct or indirect magnetization. Direct magnetization is when the electric current passes through the part and a magnetic field is formed in the material. Indirect magnetization is when a magnetic field is applied from an outside source. The magnetic lines of force are perpendicular to the direction of the electric current which may be either alternating current (AC) or some form of direct current (DC) (rectified AC).
Magnetic particle inspection is quick, inexpensive and sensitive to particularly shallow (0.003 in.) defects, surface cracks and other lineal indications.
Radiographic inspection is the best nondestructive method for detecting internal defects and hidden flaws, such as shrinkage and inclusions, simply because we are looking inside the part with short wavelength electromagnetic radiation (high energy photons) to penetrate various materials. And the radiograph serves as a permanent record of the casting quality that can be reviewed by multiple personnel.
In this method, a casting is exposed to radiation from an x-ray tube. The casting absorbs part of the radiation, and the remaining portion of the radiation exposes the radiographic film. Dense material withstands the radiation penetration, so the film is exposed to a lesser degree in those areas, giving the film a lighter appearance. Less dense materials allow more penetration and correlates to darker areas on the film. Any hole, crack or inclusion that is less dense than the casting alloy is revealed as a dark area.
Casting thickness and density will affect the range of inspection possible, depending on the energy level of the radiation.