Materials Science Forum Vols. 475-479

Abstract: Microstructures and hot deformation behaviors of spray formed superalloy GH742 have been studied in this paper. The results indicate that the spray formed superalloy GH742 has high relative density, low oxygen pickup, refined microstructure, and good forgeability. The fully inhibited coarsening of microstructure in spray formed superalloy GH742 has also been found in this study. 32wt% γ¢ and 0.5wt% carbonitrides, (Nb,Ti)(C,N) and Ti(C,N) were found in the as-deposited GH742, and most of them are sub-micrometer.

Abstract: Heat-resistant Al-Fe-V-Si aluminum alloys enhanced by in-situ TiC particles have been prepared by spray forming process with suitable process parameters. Research results show that the microstructure of as-deposited alloy is fine and homogeneous. In-situ TiC particles prevent the unsteady phases from coming into being. On the other hand, the TiC particles increase the volume fraction of heat-resistant phases. So the mechanical properties of the enhanced alloy by in-situ TiC particles are better than that of Al-Fe-V-Si alloy without TiC particles. The hot extrusion temperature is also an important parameter to understand. Under the permission, it is better to extrude the alloy at lower temperature. The tensile strength of the alloy without TiC particles is about 435MPa at room temperature and is about 204MPa at 350°C. However, when the alloy is enhanced by in-situ TiC particles, the strength of alloy is about 482MPa at room temperature and is about 224MPa at 350°C temperature.

Abstract: There are several commercial processes for producing metallic parts by selective laser sintering (SLS) followed by infiltration of a molten metal at 700-900C. These parts are used in rapid manufacturing and rapid tooling applications. The present work centers around research to produce non-metallic parts infiltrated with materials at temperatures exceeding 1300C. Specific systems include siliconized silicon carbide. Of primary concern are: process control during the high-temperature infiltration; the binder system which must bind powder together during SLS, provide structural strength continuously from room temperature to the infiltration temperature, and react favorably with the infiltrant. This research was funded by State of Texas Technology Development and Transfer Grant Number 003658.

Abstract: The authors review a laser-assisted rapid manufacturing process which allows to manufacture components from the original powderized material, overcoming functionality test limitations of conventional rapid prototyping processes. In a comprehensive experimental and analytical investigation, a set of rules which predicts the heat transfer and the geometrical properties of the fabricated parts was derived and verified. Further, the resulting set of equations was connected to a second model which predicts the mechanical properties of the fabricated parts. The results agree very well with measured mechanical properties, showing that, depending on the operating parameters laser power, scanning speed and powder delivery rate, the mechanical strength is anisotropic.

Abstract: The purpose of this experiment was to compare different techniques that help improve conventional tooling. The methods investigated were chosen from both the methods of Rapid Tooling: direct and indirect. Six different methods were selected including, Sand Casting, Investment Casting, Fused Deposition Modeling (FDM), Direct Composite Manufacturing (DCM), Selective Laser Sintering (SLS), and Stereolithography (SLA). Several industrial corporations were contacted to help complete all six tests. Five parameters were selected for the comparison of these samples: dimensional accuracy, tensile strength, surface roughness, time for completion, and weight. Through comparison the strengths and weaknesses of each method was determined. It was found that different methods did better in various parameters. However, Selective Laser Sintering (SLS) seemed to have the best overall performance.

Abstract: With a newly established 300kW twin hybrid plasma spraying system, a peculiar layered composite zirconia coating was successfully deposited. The coating is consisting of splats and dendritic columns, which come from thermal plasma spraying and thermal plasma PVD, respectively. A 120µm-thick composite coating was deposited in 10 minutes at the corresponding growth rate of 100µm/min, if the rotation of the substrates is considered. The microstructure of such composite coatings has been characterized using a variety of microscopic techniques as part of a process optimization study.

Abstract: Metallic amorphous materials have been widely developed thanks to the outstanding properties including high chemical stability, mechanical strength, and magnetic properties. However, with the exception of a few compositions, the limiting factor is the critical cooling rate for the formation of the amorphous phase. For many applications, it is only the contact surface properties that are important, thus the use of coating techniques such as thermal sprayings has several attractive features. In this paper, we present the microstructure of Ni-based amorphous coatings prepared by laser cladding and vacuum plasma spraying. The utilization of plasma spraying to deposit atomized powder enabled the formation of fully amorphous coating, laser cladding resulted in mostly crystallized structures. Glass forming ability and wear properties of the coatings were discussed as a function of the coating microstructure.