Sintered high speed steels (HSSs) are assuming an increasingly important role as wear resistant and cutting tool materials, areas in which they are in competition with cemented carbides. Research on HSSs has taken three basic approaches: use of advanced technologies such as hot isostatic pressing to produce full density materials; assessment of their sinterability under industrial conditions (nitrogen-hydrogen atmospheres, low sintering temperatures, continuous furnaces, etc.); and reinforcement with hard materials such as ceramics and carbides to increase cutting or wear performance. In the present work, which combines the last two approaches, additions of tungsten carbide and titanium carbide were made, singly and in combination, to M2 and T15 steels. Microstructures, densification, and transverse rupture strength were compared after sintering in vacuo and under a nitrogen-hydrogen atmosphere. Addition of 10 wt-% of a 90WC–10Co powder mixture to the base steels produced a marked increase in sinterability at low temperatures, resulting in better flexural strengths, but, because of its lower reactivity, titanium carbide produced little effect on densification; addition of both carbides together produced intermediate results. Acceptable levels of flexural strength can be obtained by sintering in N ₂ –20 vol.-%H ₂ atmospheres at temperatures below 1250°C, but vacuum sintering was found to be the most efficient method of producing HSSs reinforced with cemented carbides. PM/0608

In this work, the morphology of solidification of the weld zone (WZ) was studied in a joint formed from dissimilar materials, composed of austenitic AISI 304 stainless steel and Inconel 600 nickel alloy, welded with an Nd:YAG-pulsed laser. The laser beam and optical system parameters were selected with a view to obtain a weld with total penetration and good surface finish. The microstructural characterization was carried out using an optical microscope, in which a WZ was seen with total penetration, keyhole-type, presence of small pores and absence of cracks. The welded joints were also characterized by means of an electron scan microscope. Measurements taken by X-ray spectrometry for dispersion of the energy in the WZ indicated a slightly heterogeneous distribution of nickel and iron. It was seen that the start of solidification in the WZ occurred by means of epitaxial growth. The morphology of WZ solidification was basically denditric and cellular, being influenced by the temperature gradient, solidification speed and chemical composition. The variations in chemical composition and solidification morphology do not significantly alter the Vickers microhardness values in the WZ. Results obtained in the tensile tests indicate suitably effective welding values.

The aim of this study is the consolidation of Cobalt-Chromium (CoCr) alloy powder using the additive manufacturing - selective laser melting (SLM) and the investment casting techniques. The research of this study has been applied to their biomaterial applied to development of prosthesis and dental implants. The gas atomized powder are spherical (mean diameter equal to 42,74 μm) and was analyzed by their physical and chemical properties. The microstructure of the powder and specimens was evaluated using optical microscope (OM) and scanning electron microscope with energy-dispersed X-ray spectroscopy (SEM-EDS). The mechanical properties were evaluated of standard samples using a tensile (yield strength, maximum tensile, rupture tensile and elongation), three point bending (transverse rupture strength) and micro hardness tests. The mechanical results indicate higher values for the SLM than casting specimens. The micrographs revealed a characteristic morphology of laser been used in the SLM technique and the dendrites in the casting technique. The microstructure of samples made by SLM is thinner than the samples obtained in the cast.