Newsletter Sign up
Subscribe to our contact list and we'll send you important service announcments and product updates via email. Home / Qualifications / Projects
|
| Failure Analysis of High Chromium Hot Work Mill Rolls The results of an investigation of high chromium hot work mill rolls revealed the failures related to certain manufacturing practices and/or quality control. Specifically, RJLG's analysis discovered that the rolls were not heat treated properly, as evidenced by the poor microstructure of the failed rolls, which contained small amounts of secondary carbide and large amounts retained austenite. To help define the problem, RJLG experts compared a similar roll from a different supplier that exhibited good service performance. This other manufacturer's roll exhibited a microstructure consisting of eutectic carbide, secondary carbide, and only a very small percentage of retained austenite. Because of the large amounts of austenite in the failed rolls, RJLG specialists expected the rolls not to have the same level of beneficial residual compressive stresses in the roll barrel, which helps to resist cracking as evidenced by the properly heat treated roll. In addition to the high levels or retained austenite in the shell of the failed rolls, some of the rolls exhibited porosity on the shell side of the bondline and instead of a nodular iron, the core appeared to be more like a gray iron, as evidenced by the presence of poorly formed Type VIIB (rosette) flake graphite. These factors and more allowed RJLG experts to arrive at the conclusion that original rolls were not heat treated properly. The roll user user was compensated for the poor roll performance and the manufacturer was able to correct the issue with confidence. |
| Failure Analysis of IGBT Module Resistors Resistors associated with insulated gate bipolar transistor (IGBT) modules were inspected and analyzed to determine the cause of poor bond development in the chip to substrate solder joint. All failed devices delaminated at the surface defined by the titanium layer and a nickel solder phase. Titanium is not considered a solderable material, so the solder contact should have been the nickel layer. The source material for the titanium deposition contained a high percentage of oxygen. This likely affected the surface characteristics of the deposited layer and contributed to the poor bond. The poor bond quality of the resistors appeared to be related to contaminated source metal for deposition and the soldering process. The titanium source material apparently absorbed contaminants while in service which produced a contaminated titanium layer and a poor surface for deposition of subsequent metal layers. The soldering process dissolved the entire nickel layer thus further contributing to a poor bond at the titanium interface. RJ Lee Group (RJLG) determined the solder joint failures were related to the manufacturing process, specifically the backside metallization of the resistors. |
| Failure Analysis of Medical Implant Devices The number of medical devices being implanted is on the rise. Unfortunately, from time to time the device fails after implant resulting in claims by individuals, suppliers or manufacturers. RJ Lee Group (RJLG) has investigated the cause of failure for a number of different types of medical devices. The investigations have included evaluation of the raw material used in the component parts and whether they meet manufacturer specifications. RJLG experts employ a range of analytical tools including optical and scanning electron microscopy, X-ray diffraction and mechanical testing to address the questions raised in each situation. |
| Fire Related Contamination Assessment RJ Lee Group (RJLG) was retained to evaluate data and samples from a 22-story building to determine whether asbestos present was caused by a fire in the building. Samples were analyzed by stereo optical, polarized light and scanning electron microscopy to determine whether fire residue (i.e., soot) was associated with the asbestos. The results of these evaluations indicated that asbestos had indeed been distributed into other parts of the building as a result of the fire. |
| Food Processing Contaminant Source Identification RJ Lee Group (RJLG) has a long history of serving the needs of clientele in the food processing industry. Utilizing the entirety of analytical capabilities available, RJLG has identified and sourced contaminants resulting from manufacturing practices and product returns. |
