It was noted that thermal spraying of coatings provides effective protection against wear corrosion and oxidation and is widely employed to improve new parts and for reconditioning of worn parts. It was shown that Ti-based coatings are effective in producing layers to combat 'metal-onmetal' friction. The properties of Ti-based coatings were described.
Characterlsatlon of sillclde base materials for high-temperature protection V.Terentieva. (State Aviation Inst. of Technical University, Moscow, Russia.) A new silicide-based powder material, for use in coatings for high temperature protection of hot loaded components, was described. The material is based on St-TiMo modified with B, Y and W. Production of the powder was considered. The coatings were shown to have a self-healing ability. Plasma spraying and other techniques could deposit the coatings. Properties of the powders and coatings were presented.
Slntering of translucent high-alumina tubes for high-pressure sodium vepour lamps E.Labusca-Lavarescu. (Inst. Optoelectronica, Bucharest, Romania.) Sintering of 99.9%AI203, in the form of translucent tubes for lighting applications, was discussed. The factors involved in the success of this, initial powder qualit.~ compaction procedure and high temperature smtering of a very refractory, hard and non-plastic material were considered together with aspects of sealing and assembly with other components.
General topics Three.dimensional simulation of residual stresses in plasma sprayed thermal barrier coatings S.Kundas et al. (Technical University Aachen, Germany.) It was noted that thermal barrier coatings on gas turbine parts protect against overheating and allow engines to run at higher temperatures with increased efficiency. Residual stresses are an important characteristic of these coatings. Models fl)r heat transfer and stress evaluation were devel<>pod. It was shown that there is stress relaxation due to plastic deformation durra e, spraying. I-he models used showed
M ~ March 2oo3
cracking to be less than using elastic models. Cracking and crack initiation were considered.
Production of press moulds by plasma spray-forming technology Y.Borisov et al (Paton Welding Inst., Kiev, Ukraine.) It was reported that moulds for plastics forming had been made by plasma spraying Cu-AI-Fe powder on to master moulds made of non-metallic materials with little heat resistance. Structures and properties of the deposited alloys were described. It was possible, by control of deposition conditions to lower residual stresses. Material above 20ram in thickness was produced without cracks or deformation.
Opportunities for powder Injection moulding of refractory and hard materials R.M.German. (Pennsylvania State University, USA.) The powder injection moulding process was reviewed with regard to recent developments in both refractory and hard materials. Examples of applications were given. Injection moulding was compared with PM and other process routes in order to emphasise design features of PIM. PtM allows reduction or elimination of post-process machining to final dimensions of complex shapes. In the case of refractory and hard materials the same powders can be used as in other PM technology, saving costs. Future trends were shown to depend on early identification of candidate materials and designs.
Use of acoustic emission to charecterise delamlnation In tungsten base alloys H.Traxler et al (Plansee AG, Reutte, Austria.) It was noted that there is a need for a test for delamination in W alloy sheet, below 0.5ram. Reverse bend testing was shown to be suitable and acoustic emission was used to detect the instant of formation of a delamination crack and to measure the bend angle. Finite element analysis was used to determine stress distribution. It was shown that specific parameters of the rolling process influence the tendency to delaminate in a significant and reproducible manner. Other fracture patterns were observed.
EURO PM 2ooz. The Abstracts that follow are from papers presented at the 2oo~ European Congress on Powder Metallurgy, which was held In Nice, France, In October aool. i
Alloy steels Corrosion resistance and properties of PM duplex stainless steels M.Rosso, A,Grande. (Torino Polytechnic, Torino, Italy.) It was shown that there is a considerable amount of data about austenitic or ferritic stainless steels, but little concerning duplex steels. Duplex steels have good chemical and mechanical properties. The paper described researches into production of sintered two-phase stainless steels from 410L stainless steel powder and additional alloy elements, Cr, Ni, Mo, Mn etc. A range of material and process parameters was tested. Structures and corrosion and mechanical properties were presented.
Properties of hybrid slntered carbon-manganese-molybdenum steels L.Parilak et al. (Inst. Materials Research, Slovak Academy of Sciences, Kosice, Slovak Republic.) Water-atomised and vacuum annealed Fe1%Cr-0.3%Mo-0.3%V and Fe-3%Cr0.3%Mo-0.3%V powders, admixed with 1% to 3%Mn and 0.25%C were pressed and sintered at 1120°C or 1200°C. Mechanical properties and microstructures were described. Sintering at 1200°C increased tensile properties. It was suggested that these steels could be used instead of steels containing Ni.
Porous materia|s PM production and properties of porous titanium M.Bram et al. (Forschungzentrum JiJlich GmbH, JLilich, Germany.) PM production of porous Ti was investigated with reference to properties, including compaction behaviour, of the Ti powder, pore-forming materials and mixtures of both. The pore former was found to have lubricating effects. Effects of process conditions on shrinkage were studied. Densification of the Ti network was the prime cause of shrinkage. Production of porosity graded structures was possible. Static loading fracture toughness was evaluated.