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.
Properties of Metal Injection Molded Products Using Titanate-Containing Binders
MIM parts usually require a green strength high enough to withstand handling, particularly after molding and before sintering. Thus, it is necessary to develop a binder system that can provide a high green strength without impairing molding and debinding properties. In this study, a titanate coupling agent was evaluated as a processing aid. The results showed that a higher green strength and a lower amount of swelling during solvent debinding were attained. Due to the presence of Ti atoms in the coupling agent, the sintered density and hardness also increased slightly. Scanning electron microscope observations confirmed that the presence of the titanate coupling agent resulted in improved bonding between the metal powder and the binder.
Sliding wear of 304 and 310 stainless steels
Abstract Blocks of 304 (metastable) and 310 (stable) austenitic stainless steels were tested in argon against M2 tool steel rings. Scanning, transmission and scanning transmission electron microscopy analysis, together with microhardness measurements, showed that the strain-induced martensite transformation in 304 steel affects the form and composition of the wear debris and the nature of the transfer layer. The hardness of the transfer layer relative to the hardness of the adjacent deformed base material is also important, as shown in earlier work on Cu-Be. During early stages of sliding, the friction values for both alloys are similar, but whereas the friction continues to rise smoothly to a steady state value for 310 steel, the formation of α'-martensite in 304 steel gives a lower average value of friction coefficient with large fluctuations.