Showing papers by "Robert F. Singer published in 2006"

Influence of topologically closed packed phase formation on creep rupture life of directionally solidified nickel-base superalloys

Abstract: Several experimental superalloy compositions based on the alloy IN792 were investigated. Creep rupture properties were measured and microstructures in the as-heat-treated condition and after creep rupture testing were evaluated. Two types of topologically closed packed (TCP) phases have been observed. Type 1 occurs in alloys with increased additions of the γ′-formers Al and Ta and shows detrimental effects on creep rupture life. Type 2 precipitates in Re-containing alloys are much smaller in size and volume fraction than type 1 and are found not to influence the creep rupture properties. The different effect of type 1 and 2 TCP phases can be rationalized in terms of the amount of precipitate and the resulting matrix depletion of solid solution strengtheners.

CVD diamond coating of steel on a CVD-TiBN interlayer

Abstract: Adherent and homogeneous diamond films were deposited on 41Cr4 steel substrates employing c hemical v apor d eposited (CVD) TiBN interlayers. The suitability of CVD-TiBN interlayers for diamond deposition was investigated. The CVD intermediate layers showed excellent barrier properties against the diffusion of iron from the bulk substrate to the surface and against diffusion of carbon from gas phase during diamond deposition. Various growth conditions for interlayers affect their thickness and composition. For these samples different shares in the phases TiB 2 and TiN were analyzed by XRD. The diamond coating onto the TiBN interlayer showed very good adhesion. The measured Raman spectra proved high compressive stresses in the diamond film with a high diamond quality. Sandblasting tests indicated an enormous improvement of the erosion resistance after diamond deposition on 41Cr4 substrates with a 5 μm intermediate layer of TiBN.

Method for the production of a composite material or a precursor product for the production of a composite material

Abstract: The invention relates to a method for the production of a starting product for the production of a composite material having a metallic matrix phase and a reinforcement phase, with the following steps: Providing an extruder device having a die (4), Feeding the metallic matrix phase in a first portion of the extruder device, Transport of the metallic matrix phase in the direction of the die (4), Feeding reinforcement particles forming the reinforcement phase in the region of a second portion of the extruder device, Partially melting the metallic matrix phase by heating it up to a temperature between the solidus and the liquidus temperature. Producing a mixture formed from the reinforcement particles and the at least partially melted on metallic matrix phase and further transport of the mixture through the die (4) .

Effect of grain boundary characteristics on hot tearing in directional solidification of superalloys

Abstract: The effect of grain boundary (GB) misorientation on hot tearing susceptibility of directionally solidified (DS) nickel-based superalloys was explored. We found that the castability of second generation nickel-based superalloy CMSX-4 is inferior to DS superalloy IN792, an alloy well known for bad castability. The castability of CMSX-4 is somewhat improved at a higher solidification rate. The hot tearing tendency increases with increasing GB misorientation angle. As feeding tendency becomes greater with increasing misorientation, this points to the importance of GB cohesion for solidification cracking in the alloy. Microstructure investigation reveals that hot tearing is associated with formation of continuous gamma and gamma prime eutectic films at the GB in CMSX-4. We assume that the gamma and gamma prime eutectic, which reflects the remaining liquid at the end of solidification, prevents the impinging dendrite arms from touching and in this way decreases cohesion.

Deposition of uniform and well adhesive diamond layers on planar tungsten copper substrates for heat spreading applications

Abstract: For a more effective heat spreading we deposited thick diamond layers on tungsten copper substrates, which are used as heat sinks in the microelectronic industry. Disadvantages of high growth rate CVD techniques like microwave plasma assisted CVD (MWPACVD) or DC plasma jet CVD are the need for flat and preferable discoidal substrates, the limitation of the total substrate surface and the uniformity of the deposited layers. Thus, the uniform deposition of diamond on a large number of substrates with a rectangular or more complex geometry (like a 3D geometry) is limited. By using hot filament CVD (HFCVD) the reactor size is not limited and it is possible to increase the batch size. Even at typically lower growth rates in HFCVD the total coated surface can over-compensate this disadvantage and renders HFCVD economically more viable. We were able to scale up the number of substrates per HFCVD batch up to 240 pieces which is equal to a coating surface of 480 cm 2 . The substrate temperature was kept between 820 and 870 °C to avoid copper diffusion to the surface and evaporation of copper. An average diamond growth rate of 0.23 μm/h allows the deposition of diamond layers in less than half of the time necessary by using, e.g. microwave plasma assisted CVD at typical process conditions for the same surface (1 μm/h growth rate; substrate temperature of about 850 °C; 45.5 cm 2 coating surface per batch). In spite of the significantly increased coating surface it was possible to deposit uniform diamond layers with a high diamond quality. A further challenge is the bending of the substrates during cooling down caused by the different coefficients of thermal expansion for diamond and WCu. Cooling devices require a planar geometry. It was possible to prevent the substrates from bending after cooling down by using a special pretreatment.

Production of component integrating (sic) cast component involving by permeable jacket material and casting useful in casting threaded pins-, headless bolts-, grub screws- and threaded bolts with spraying partially liquid material into mold

Abstract: Production of component (5) integrating cast component involving:envelopment of the component (5) by a permeable jacket material (4), insertion of component (5) in a mold (1), closing of the mold, spraying of a partially liquid material into the mold, so that part of the component (5) is form-closed (sic) in a material and cooling of this material until form (sic) stability is achieved. The jacket material can be:fabric, netting, knitted material, grating (sic), nonwoven or casing. An independent claim is included for a cast material.

Continuous extrusion pressing for metal powder mixtures involves mixing metal powder and additives together with pressing agents, introduce mixture into extruding press and removing extruded section

Abstract: The continuous process involves making a mixture of metal powder and additives as well as pressing agents, introducing the mixture into an extruding press and then removing the extruded section. The additives are preferably selected from propellants, processing agents, hard materials, fibres and combinations thereof. Independent claims are also included for the following: (a) the use of extruded part as foamable semi-product for metal foam production; and (b) mixture of metal powder containing a pressing gent selected from organic and inorganic substances.

Powder Injection Moulding (PIM) of Mesophase Carbon with Water-Based Binders

Abstract: Since there are no net-shape techniques for complex parts made of mesophase carbon available yet, this work focuses on a powder injection moulding (PIM) approach. The single biggest problem to overcome here is the overlap of debindering and pyrolysis/sintering of mesocarbon when using conventional binders, causing high porosity and cracks. Water-based binders with agar as gelling agent can avoid this problem effectively by removing the binder in an optimized drying step. The subsequent sintering can then be carried out at high heating rates, leading to better densification and good mechanical properties. Furthermore, the dependency of the rheological properties of the water-based feedstock on its water content is investigated.

Influence of Pressure and Heating Rate on the Mechanical Properties of Mesophase Based Sintered Parts

Abstract: This work focuses on the influence of different sintering parameters on the mechanical properties of pressed and sintered mesophase based parts. In a first approach we analyzed the influence of the heating rate on the sintering process and in subsequent experiments we applied inert gas pressure up to 1000 bar.