Effect of Sintering Parameters and Powder Characteristics on the Performance of Metal-Injection-Molded SKD 11 Parts
—Metal-injection-molded parts were fabricated using three kinds of SKD11 powder under different sintering parameters and with different binders and additives. An analysis of the microstructures and mechanical properties of these metal-injection-molded parts revealed that the porosity decreased and the grain size increased when the sintering isothermal holding increased. The average grain size was smaller for the part made of gas-atomized powder than for that made of water-atomized powder under the same sintering condition. The microstructures consisted of (Fe,Cr) solid solution substrates and Cr 7 C 3 carbide precipitates for the sintered part. For the specimen containing 10 wt % Fe, the mechanical property decreased due to less chromium carbide precipitates. The wear resistance and hardness of the sintered part made of gas-atomized powder were superior to those of the part made of water-atomized powder. In the pin-on-disk wear test, adhesive wear and a lower friction force were observed on the specimen with a lower hardness value. On the other hand, abrasive wear and a higher friction force were found for the specimen with a higher hardness value.
Wear behavior and mechanical performance of metal injection molded Fe–2Ni sintered components
Abstract The microstructure, mechanical properties, and wear behavior of two key components of a hinge fabricated from a metal injection molding process that was then sintered and heat treated under various conditions were analyzed using an optical microscope, a pin-on-disk tester, an open-closed reciprocal wear tester, and a scanning electron microscope. Optical photomicrograph revealed a serious decarburization in the sintered component, suggesting that an increase in carbon content would be necessary to improve mechanical properties. At the initial stage of the open-closed reciprocal wear test, the obverse inclined planes of both components exhibited plastic deformation and depression. As the number of test cycles increased, an increase in cold welding, metal adhesion, spalling, delamination, and surface fatigue was observed, triggering a decrease in metal thickness, which in turn altered the shape of the components. In this study, the optimal parameters to satisfy commercial application requirements were obtained when the components were carburized at 870 °C for 30 min, quenched in oil, and finally tempered at 250 °C for 1 h.
Robust solutions of inverse problems in electromagnetic non-destructive evaluation
Non-destructive testing (NDT) is the application of physical measurement technology based on energy interaction with the material and its nonconformities. The material's response is sensed by transducers and sensors which?in most cases?scan the component and document the results in inspection images. However, NDT measures a physically defined quantity or even an intrinsic property. The difference between non-destructive evaluation (NDE) and NDT is in the interpretation of the inspection data. NDE has to discuss the inspection results in terms of quality elements and characteristics which are relevant to describe the fitness of the material for use. In the case of macroscopic defects these are the kind of defect (cracklike, globular) and its size and orientation to the main stress directions; in the case of material property determination the parameters are mainly mechanical properties. Therefore, in NDE one has to solve inverse problems. The solution of inverse problems based on mathematical procedures such as integral equations is a strong developing discipline and most of the articles prepared for this special issue of the journal have the objective of discussing the latest state of the art in that field. However, practical NDE needs robust and quick solutions which are to be applied mainly online. Therefore, we present here inversion procedures based on multiple linear regression algorithms applied to inspection data. We describe the calibration procedure to fit the free parameters of the model functions and give examples of practical applications in industry.