Plasma spraying, originally a surfacing technology used for ceramic coating of metal and non-metal substrates, is suitable for the production of bulk ceramics of almost any size with characteristic mechanical and thermomechanical properties. The porous lamellae grain structure of these composites results in a low E-modulus and strength, and in extreme thermal shock resistance, which is enhanced by the comparably high-fracture resistance of the material. Due to these properties and their low hardness, ''plasma ceramics'' can easily be machined by almost conventional methods of metal processing.
On a decrit une nouvelle approche en mettant en correlation la microstructure et les proprietes mecaniques du fer fritte et en tentant une description plus realiste de la microstructure. Dans cette partie les parametres microstructuraux importants sont discutes et on a soulignes le fait que la metallographie tend a donner des informations incorrectes sur la microstructure elle-meme, en particulier en ce qui concerne la connection entre les pores. On a aussi decrit les conceptes importants de la litterature. On a montre que frequemment ils sont issus d'idees idealistes sur la microstructure du fer fritte, ce qui restreind l'application des modeles respectifs a des cas particuliers
The principles of operation and utilization of a new stroboscopic/laser video camera system are described. The system was designed for use as a diagnostic tool in the characterization and improvement of various high-luminosity processes driven by combustion, plasma, or laser power sources. It is especially useful for processes involving powder materials or molten spray, such as thermal spray, spray forming, and metal cladding. The potential for real-time monitoring and feedback control of such processes is also described, based upon the availability of modern low-cost image processing computers and software. Included are examples of video imagery taken from . both plasma and laser-driven processes.
On a mesure la durete d'echantillons cylindriques de fer frittes et traites a la vapeur le long de l'axe du cylindre. En mesurant la densite locale le long du profile de durete, on a obtenu la correspondance durete-densite
Room temperature creep tests were performed with sintered pure Fe and differently alloyed sintered irons. At nominal stresses far below the 0.2 % offset yield strength, considerable creep strains were determined which result from micro-plastic deformations and crack opening effects. The creep strains of the liquid phase sintered alloys were much smaller than those of pure Fe.
The attempt is made to understand the role of rigid inclusions in the consolidation process of a metal powder. For this purpose, a nickel-base superalloy powder was mixed with alumina particles and consolidated by hot isostatic pressing. Densification kinetics were estimated from interrupted HIP tests and compacted specimens were observed by means of microscopy. Simple compression tests were also performed on dense samples at high temperatures. From these results, explanations for the retardation in densification due to inclusions are suggested.
The microstructure-property relationships are described for sintered plain iron using a new concept for microstructural description. Mechanical properties are listed which were experimentally obtained by widely varying the manufacturing parameters. Microstructural description was carried out on fracture surfaces of samples impact-tested at 77 K and fatigue-tested, respectively. The actual load-bearing cross-section was determined experimentally and the fraction of interconnected porosity could also be determined from the impact surfaces. The principal mechanical properties could be described by the load-bearing cross-section without any fitting of parameters being necessary, the correlation being linear with the exception of Young's modulus and elongation.
A new atomizing process is presented by which metal or ceramic melt streams are drawn by parallel gas flows at high velocity, preferably in the sonic and supersonic speed range, and attenuated to a monofil of low diameter until it bursts into pieces when passing a Laval nozzle. Contrary to known processes, the gas flow around the melt monofil is laminar. After cooling, globular particles are formed. The particle size distribution is narrower than in the case of common turbulent desintegration procedures and energy consumption is lower. A mathematical description of the main dependencies is given in simple gas dynamic relations. The economical strength of the process applies to powders significantly below 100 mum. It was successfully applied to melts at about 2000-degrees-C. Results have sofar been achieved for metal melts, whereas ceramic melts may desintegrate into powders, but fibrous particles are also possible, depending on the relation of viscosity to surface tension. Uses in the field of MIM and for special metal structures from rapid solidification (RS) are briefly reported. The name of the process, "Nanoval" came from atomizing into the nano range by a flow generated in a Laval nozzle.
Observations of fractures of sintered steels made from Distaloy SA powder alloy with various carbon contents are presented. Observations of fractures and chemical analyses at discrete areas of the specimens were performed by means of analytical scanning electron microscopy. The alloy steels such as Distaloy SA were obtained by pressing and sintering. The following mechanical properties were determined and discussed: modulus of elasticity (E(OF)). hardness (HV20), tensile strength (R(m)) and elongation (A5).
Surface engineering to improve the wear resistance of surfaces is reviewed. Advances in powder production, process control and modeling as well as application techniques are described Determination of the appropriate thermal spray coating and spray process. industries and typical components requiring these coatings are discussed. The various wear processes and coatings used to counter wear are briefly reviewed. The Gator-Gard (registered trademark) plasma spray process is reviewed along with its utilization in applying several types of protective wear coatings for various aerospace and industrial applications.
