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.
As práticas profissionais no campo público de atenção à saúde bucal: o caso de dois municípios da Bahia
This paper examines the working facilities and processes of dentists in the primary healthcare systems of two towns in Bahia State, Brazil, striving to analyze the extent to which factors related to dental care, training, placement and professional profiles influence their practices. Semi-structured interviews were conducted with nine dentists in both towns, with work process organization patterns in Municipality C being closer to the structuring principles of Brazil's National Health System than in Municipality E. This seems to be related to management characteristics, with networking links among individual, collective, and preventive clinical activities and planning noted in Municipality C. Despite these differences, the practitioners presented similarities in terms of dual militancy and perceptions of the public and private healthcare fields. The hegemony of the private sector seems to be influencing the professional practices of dentists in the public health system.