Alwin Schulz

Synthesis of single phase i-AlCuFe bulk quasicrystal by spray forming

Abstract In the present study, an icosahedral single phase bulk quasicrystalline material based on Al62Cu25.5Fe12.5 has been synthesised by a spray forming route. Microstructural characterization showed an average grain size of 10 μm. The oversprayed fine powder showed the presence of β- and λ-phases, whereas, the deposit consited of the fully single phase bulk quasicrystalline material with compositional homogeneity. The hardness and fracture toughness measurements were carried out at different indentation loads of 50–500 g. The hardness values varied in the range 10.4–8.1 GPa and fracture toughness was seen to decrease with increasing load. The varionan of hardness with load, which is known as indentation size effect (ISE), has been established clearly. Fracture toughness value was constant in the load range from 200 to 500 g at 1.2 MPa m1/2. The cracking pattern after indentation at higher load has been observed to be intergranular as well as transgranular. The evolution of the single phase bulk quasicrystalline material has been discussed in light of the unique combination of atomization and deposition process elements in spray forming technique.

Influence of carbon and chromium content and preform shape on the microstructure of spray formed steel deposits

Given appropriate control of spray- and substrate-movement spray forming can be used to produce a variety of preforms. The microstructure obtained is governed by the thermal conditions during the spray forming process which can be influenced by the material properties, the atomization and deposition conditions. Within this study, the influence of carbon and chromium content as well as the preform shape on the microstructure is investigated. As master material unalloyed steels with low and high carbon content (SAE 1015, SAE W110 and SAE 52100) have been selected. Billets, plates and parts with defined geometry have been spray formed using different atomization gas pressures and comparatively examined by quantitative metallography and density measurement. It is found that the carbon content and the atomization gas pressure strongly influence the development of porosity. Also the state of the mould surface plays an important role. In contrast, the variation of preform shape and chromium content reveals no significant change.

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.

Scanning acoustic microprobe analysis for testing solid state materials

Abstract A survey of analytic techniques for subsurface inspection by means of acoustic reflective microscopy is presented. The measurement of the acoustic material signature is carried out using a computer-assisted scanning acoustic microscope operating at frequencies between 100 and 400 MHz. Thickness measurements of surface layers and the detection of subsurface defects with descriptive parameters are pointed out. The examination of stress states in the surface comprises methods for measuring the change in the surface acoustic wave velocity with applied stress. Some typical results obtained for solid state materials are shown. Advantages and limitations of alternative measuring techniques are discussed.

Application of a Composite Hot Shearing Tool Manufactured by Co-Spray Forming

In modern manufacture, like in automotive industry, high quality products and high output rates as well as low costs are achieved by highly efficient processes. Optimized tool design represents a key factor for such processes, leading to long tool life and hence to low tooling costs. Early in the industrial manufacturing chain of roller bearings for example, hot bars are sheared into billets, which are subsequently transported automatically to the first forming stage of a press. The shear blades should have a high wear resistance at high temperatures. In this study the first bi-metal composite shear blade made by spray-forming has been developed and tested in industrial environment. The composite tool has been deposited in a co-spray forming process to directly combine a hard-facing alloy layer with a hot working steel body in order to take advantage of the high microstructural homogeneity and the low segregation generated in spray forming. After machining, heat treating and quality inspection of the new material composite, the hot working tool was used in manufacture to prove its wear resistance and durability. The results show that the interface properties of the composite are of high quality and the material has a lower vulnerability to cracks after use in production than the conventional tool, respectively material. Only the porous zone near the interface leads to fissures which are partially going deep into the tool. Hence the parameters of the co-spray forming process need to be improved.

Spray Forming of Homogeneous Bearing Steel of Minimized Distortion Potential

To minimize the distortion potential of bearing steels, 100Cr6 steel has been spray formed for the manufacture of ring shape components in this study. Structure characteristics of the spray formed bearing steel have been investigated. Evaluation of distortion of bearing components after machining and heat treatment have been made in comparison with continuous cast material. Spray forming has been approved to be an alternative approach to conventional continuous casting for the production of homogeneous 100Cr6 bearing steel of lower distortion potential.

Spray forming of low volume preforms

The aim of the current study is to examine the influence of substrate temperature and the processing parameters on the microstructural development during spray forming of flatproducts and shaped ingots. Unalloyed steel grades with different carbon contents were used to investigate additionally the question of whether the freezing range is influencing the development of cold porosity.