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.
Improvement of AISI D2 steel properties by unconventional vacuum heat treatments
Abstract The possibility of improving the properties of an AISI D2 steel by an unconventional vacuum heat treatment has been studied. A double quenching, the first quenching from a temperature higher than that for the second quenching, followed by normal tempering enables an excellent combination of toughness and hardness to be obtained as a consequence of (a) the improved microstructural homogeneity due to the dissolution (first quenching) and reprecipitation (second quenching) of carbides, (b) a large amount of fine dispersed carbides in the matrix, (c) a low carbon content of martensite and (d) the possibility of maintaining in the matrix a controlled amount of retained austenite, which plays an important role during the fracture and wear processes. Vacuum furnaces rather than salt bath furnaces are particularly suitable for this double treatment; in addition to the well-known advantages, their flexibility permits several process conditions to be tested in a less expensive way and tools to be produced with properties optimized in relation to the use to which they are subjected.
Sliding wear behavior of stainless steel parts made by metal injection molding (MIM)
Abstract The wear resistance of stainless steel parts, which were fabricated by a metal injection molding (MIM) process, was studied under self-mating, dry sliding conditions, using a pin-on-disk type wear configuration. The materials used were an austenitic stainless steel 316L (of MIM and wrought steel), a precipitated stainless steel 17-4PH (of MIM and wrought steel) and a widely used ball-bearing steel (DIN 100Cr6). Two surface conditions, i.e. as sintered and as polished, were considered in the wear tests of the MIM samples. In summary, the wear resistance of 316L was lower than 17-4PH, and the latter was almost the same as 100Cr6. Further, the wrought materials showed a better wear resistance than the MIM materials. The mechanisms responsible for these tendencies were discussed by means of microscopical observations and chemical inspections of the worn surfaces and the microstructures of the samples.