Showing papers on "Spray forming published in 1991"

Mathematical modeling of the isothermal impingement of liquid droplets in spraying processes

Abstract: A mathematical representation has been developed and computed results are presented describing the spreading of droplets impacting onto a solid substrate. Problems of this type are of major practical interest in plasma spraying (PS) and in spray forming (SF) operations. While the present study was confined to the fluid flow aspects of the process, information has been generated on both the final splat dimensions and on the time required to complete the spreading process. Through this treatment, it is possible to relate these quantities (the splat size and the spreading time) to the operating conditions,i.e., droplet size and droplet velocity, and material properties. The theoretical predictions were found to be in good agreement with both Madejski’s asymptotic solution[17] and with available experimental results. For typical SF conditions (droplet sizes in the 100-µm range and droplet velocities in the 100 m/s range), the spreading times were of the order of microseconds,i.e., significantly shorter than the estimated solidification time.

Property enhancement in Type 316L stainless steel by spray forming

Abstract: Type 316L stainless steel was processed by rapid solidification, liquid dynamic compaction (LDC) and subjected to a series of simple thermomechanical treatments (TMT) to produce a fine austenitic grain structure. The as-deposited, fine grained structure was rollable in excess of 80% at liquid nitrogen temperature (77 K) without annealing or edge cracking. High tensile and yield values resulted from the cold worked austenitic structure at 298 K and from martensite formation on rolling at 77 K. Ductility values were on the low side but at useful levels for these high strengths.

Spray forming of aluminium-copper alloys

Abstract: The thermal conditions on the top surface of an Al-4wt.%Cu alloy billet during spray forming have been monitored using an infrared thermal imaging camera. The thermal history of the billet top surface on the axis of the spray plume has been correlated with through-thickness measurements of equiaxed grain size, porosity and segregation. Transmission electron microscopy shows that a high dislocation density in the as-sprayed billet may be relieved by subsequent heat treatment, which also causes precipitation of θ′ from the α-Al matrix.

Metal matrix composites made by spray forming

Abstract: Spray-formed metals have a finer structure, near zero segregation and improved mechanical properties resulting from rapid solidification, when compared with conventional materials. A further benefit of spray forming is that it gives greater freedom to add any second or third phase, liquid of solid, by entraining a stream of the added phase into the atomized spray before deposition. This paper shows that metals matrix composites made by spray forming can incorporate both of these benefits in one operation. A comparison with the equivalent materials made by powder metallurgy or by the melt mixing route is made.

Reactive spray forming process

Abstract: A reactive spray forming process comprises generating a molten spray of metal, and reacting such molten spray of metal in flight with a surrounding hot metal halide gas to form a desirable alloy, intermetallic or composite product. The molten spray of metal may be directed towards a cooled substrate and the alloy, intermetallic or composite product collected and solidified on the substrate.

Modelling of Spray Forming

Abstract: This paper discusses the spray forming method for manufacturing alloys and metal matrix composites. In particular, attention is concentrated on available modelling techniques for the follow...

Low flow rate nozzle and spray forming process

Abstract: RD-19,940 ABSTRACT OF THE DISCLOSURE An improved nozzle which allows molten metals to be sprayed at low metal flow rates. This is useful for the Plasma Arc Melting process which used a hearth to prevent ceramic inclusions in the end product. The new nozzle design avoids metal freeze-off at the nozzle tip because a bore insert is positioned into a standard nozzle. The bore insert is a conduction heater, e.g., it is fabricated from boron nitride or the like. In use, molten metal is in contact with the insert so it maintains the insert at about the temperature of the molten metal; this then maintains the nozzle tip at a higher temperature than that of a standard nozzle. Freeze-off in the nozzle is non-occurring as long a molten metal is in the crucible.

Spray forming polymer membranes, coatings and films

Abstract: A method of forming a polymer film having controlled physical and chemical characteristics, wherein a plume of nebulized droplets of a polymer or polymer precursor is directed toward a substrate from a converging/diverging nozzle having a throat at which the polymer or a precursor thereof is introduced and an exit from which the nebulized droplets of the polymer or precursor thereof leave entrained in a carrier gas. Relative movement between the nozzle and the substrate is provided to form a polymer film. Physical and chemical characteristics can be controlled by varying the deposition parameters and the gas and liquid chemistries. Semipermeable membranes of polyphosphazene films are disclosed, as are a variety of other polymer systems, both porous and non-porous.

Method of forming article with variable composition

Abstract: A method of forming a structure having multiple alloy properties involves spray forming and employs a single alloy system which is subject to modification by addition of modifying elements. The initial part of the structure is made of the alloy (16) by application to the substrate without the modifiers present. The modifiers (32) are added to mix with and dissolve in the alloy in a dispensing crucible (12) supplying the spray forming operation and the coating operation is then continued. The latter portions of the structure have modified alloy content and properties which are modified based on the modification of alloy content. The metal melt may be of a nickel base superalloy and the modifier metal may be aluminium.

Manufacture of wire rod with spray forming

Abstract: PURPOSE:To drastically improve toughness by applying plastic deformation to a raw shaped material of powder tool steel manufactured with spray forming method under the specific forged ratio. CONSTITUTION:For example, in the case of manufacturing a wire rod as raw material for piston ring, to the raw shaped material 17 of powder tool steel manufactured with the spray forming method, the finished product is obtd. through the well-known forging process 18, rolling process 19, wire drawing process 20, heat treatment process 21 and ring working process 22. Then, at the time of using So (cm ) for sectional area of the raw shaped material 17 and Sf (cm ) for cross sectional area of the wire rod after applying the plastic deformation of forging, rolling, etc., the spray forming is executed so as to satisfy the condition of forged ratio So/Sf>=80. By this method, the wire rod without any stringer structure and greatly improved in toughness is obtd.

Method of forming dual metal structures

Abstract: A method for forming a structure having an inner portion of a first metal and an outer portion of a second metal involves employing a spray forming processing. The beginning stages of the spray forming is performed with a first metal (22) in a dispensing crucible (24) which supplies a stream of the first metal to an atomization zone (14) where the stream is broken up into many droplets which are driven by an atomizing gas onto a receiving surface (10). The second stage of the processing (Fig. 2) involves adding small quantities of a second metal (28) to the dispensing crucible before the first metal is completely drained therefrom to permit a blend of the two metals to be formed on the preform between an inner and an outer portion thereof. The third phase of the method is the addition of the second metal to the dispensing crucible so that the latter stages of the spray forming is performed with the second metal and accordingly that the outer portions of the preform are formed of the second metal. A desirable good metallurgical bond is formed between the inner and the outer portions of the preform. The first and second metals may both be nickel base superalloys.

Advances in powder metallurgy - 1991. Vol. 5 - P/M materials; Proceedings of the Powder Metallurgy Conference and Exhibition, Chicago, IL, June 9-12, 1991

Abstract: The present volume powder metallurgy materials discusses the state of the PM industry, a metallurgical evaluation of new steel powders, design criteria for the manufacturing of low-alloy steel powders, and homogenization processing of a PM maraging steel. Attention is given to the corrosion resistance of full density sintered 316 SS, the performance characteristics of a new sinter-hardening low-alloy steel, wear performance of compositions made by low alloy iron/high alloy powder mixtures, and the strengthening of an AISI 1020 steel by aluminum-microalloying during liquid dynamic compaction. Topics addressed include the influence of alloying on the properties of water-atomized copper powders, fundamentals of high pressure gas atomization process control, advanced sensors and process control of gas atomization, and bimetallic tubulars via spray forming. Also discussed are factors affecting the delamination of PM molybdenum during stamping, applications of powder metallurgy molybdenum in the 1990s, and powder processing of high-temperature oxides.