Chengsong Cui

Modeling and Simulation of Spray Forming of Clad Deposits with Graded Interface Using Two Scanning Gas Atomizers

A three-dimensional shape model based on a surface coordinate tracking method has been developed for clad deposits with graded interface which are spray formed using two scanning gas atomizers. The calculation of element distributions in the deposits has been incorporated into the shape model. On this basis, the deposit shape and the element distributions in the deposit have been simulated. It shows that the scanning mode of the atomizers and the degree of overlapping of the two sprays play important roles in the spray forming of clad deposits. A concentration gradient of chemical elements in the deposits can be achieved under proper processing conditions. Finally, the modeling and simulation of the spray forming of clad deposits have been validated by experimental investigations.

Characterization of as-Spray-Formed Products

Spray-formed materials are characterized by fine and homogeneous microstructures and typically show much better hot workability than conventional materials. On the other hand, porosity is commonly present in spray-formed materials, and in the worst case cracks and significant segregation may appear. Over the past two decades, a considerable amount of research has been devoted towards characterization of spray-formed materials. A variety of techniques have been used to investigate them with regard to material homogeneity, porosity, grain structure, phases, solid solubility, inclusions and hot workability. For example, segregation has been investigated by means of SOES/GDOES on the macro scale and by means of electron microprobe analysis on the micro scale. Porosity has been measured and studied by means of the Archimedes’ method, optical microscopy and image analysis techniques. Microstructures have been examined and evaluated by means of optical microscopy, XRD, SEM + EDX, etc. Size, shape, and distribution of precipitates/carbides have been quantitatively evaluated by means of image analysis. Deformation behavior of spray-formed materials has been studied by means of compression tests. In addition, soundness has been analyzed by color penetration tests. This chapter will focus on the characterization of spray-formed materials in the last two decades. The most effective and widely used techniques for the material characterization will be described, and the representative results of the investigations will be presented.

Co-spray-formed graded steel for micro rotary swaging tools

Micro rotary swaging tools are required to have different material properties in different functional areas. These requirements can be fulfilled by applying different materials in the specific regions of the tools. The different materials can be combined with a gradient zone in between to reduce critical stresses at the interface during heat treatment and in swaging process. Such graded tool materials are supposed to be manufactured by means of a newly developed co-spray forming process. In this study, a flat deposit of graded tool steel (HS6-5-3C/HS6-5-2C) was produced via co-spray forming, followed by hot rolling and heat treatment. Micro infeed rotary swaging tools with fine geometrical structures were precisely machined from the graded steel. The tool performance during swaging of stainless steel wires was evaluated.