Alexei L. Petrov

Laser synthesis of functional graded filter elements from metal-polymer powder compositions

Perspectives of laser synthesis of functional graded materials (FGM) with controlled pores and chemical mixture are discussed. Filter elements from metal-polymer powder compositions were fabricated by the selective laser sintering method. It was shown that physical properties of the composited 3D part can change from layer to layer and have no nature analogy. In particular, permeability and porosity coefficients of synthesized 3D parts were determined depending on laser influence parameters and a polymer quantity. Wide opportunities of preliminary computer modeling of the porous space structure, the forecast filtration characteristics are discussed.

Formation of intermetallic phases under laser sintering of powdered SHS compositions

The process of controlled laser sintering for powdered SHS compositions with the bases Ni-Ti and Ni-Al was realized. The optimal parameters of laser effect, under which the reaction of SHS proceeds in controlled regime, were determined. The phase composition of the sintered structure was revealed by the x-ray phase analysis. In particular, it was shown, that the NiTi-material with shape memory effect, perspective for using in medical implantation, is the basis for forming intermetallic phase under laser sintering of Ni_Ti powder compositions.

Structure and properties of porous PZT ceramics synthesized by selective laser sintering method

A method of layer by layer selective laser sintering is prosed to synthesize structural piezoelectric elements out of PZT ceramics. The dependence of density of sintered elements on the regimes of sintering was investigated. X-ray diffraction and x-ray phase analysis were performed. It is shown that phase content and lattice structure had changed as a result of laser treatment.

Getting protective high-temperature coatings on carbon-carbon composites by means of laser beam

Experimental investigations of getting protective high temperature coatings on carbon-carbon composites by means of laser cladding were accomplished. The reactionary formation of coatings was investigated during laser melting of powders Si - C and Si - Mo. It was stated that the high quality of coatings is provided by the presence of free silicon. The adhesion strength of siliceous coatings with carbon materials exceeds the shear strength of the carbon-carbon composites. The optimum parameters of processing, structures and thicknesses of protective layers were determined. The microstructure of laser coatings were investigated by means of metallographic microscopy and by a method of the x-ray phase analysis.

Laser-beam pattern cutting of carbon-carbon composites

Particularities of using CW and pulsed-periodic laser radiation for cutting sheet carbon-carbon composites material and carbon fabric were studied. The processes of shaping the channel of evaporation, ways of reduction of zone of thermal influence and increasing of quality under laser cutting carbon-carbon composites were considered. Structure and phase composition of carbon in zone of thermal influence were explored. It is shown that use of pulsed- periodic laser radiation for cutting carbon composites material allows to greatly reduce or practically completely exclude the zone of thermal influence and perfect the quality of cutting. Laser cutting is one of the most perspective ways of dimensional processing of carbon-carbon composites.

Influence of laser treatment on the structure and properties of carbon-carbon composites

An experimental investigation of influence of laser radiation on the phase composition of carbon-carbon composites with different types of non-graphitizing carbon matrix and fabric fillers was made. It was shown that laser treatment formed a graphite-like structure of material. The process of graphitization is a heterogeneous crystallization. The monochromatic reflectance was measured of carbon-carbon composites within the range of 0.4 to 1.06 micrometers and 10.6 micrometers before and after laser treatment. It was shown that laser treatment causes sharp increase of oxidation of stability carbon-carbon composites in ambient air under elevated temperature.

The conditions of Selective Laser Sintering of Metal-Polymer Compositions

Multiple layer SLS is a one from perspective method of such speed CAD modeling. Under selectivity we consider a possibility to scan of a laser beam over the free powder material surface by the some contour with account for the laser influence dose in each point. Specificity of such problem and her difference from the known technology of the laser cladding and soldering is joining with skill to obtain as a large as small layers of a sintering structures with a space resolution by the layer ~0.1 — 0.3 mm.

Auto-oscillating ODMV plasma upon 500-W cw CO2 laser radiation exposure and influence on metal surface treatment

Auto oscillating surface optical-discharge plasma was formed in a metal vapor under normal conditions by steady-state irradiation with a cw CO2 laser delivering radiation of moderate (2 - 4.5 MW/cm2) intensity. A strong screening of the metal surface, which caused even completely stop evaporation of the metal, was observed. The auto oscillations were also the reason of vibrational process in the metal pool. Influence of the phenomena on metal surface treatment was discussed.

Influence of laser-induced capillary waves on heat and mass transfer in the arc-augmented laser processing of metals

An experimental study is reported of the influence of capillary waves on heat and mass transfer in molten metal during gas tungsten arc (GTA)- augmented laser processing by cw CO2-laser radiation of q approximately equals 2- 4.5 MW/cm2 intensity. Capillary waves excited on the melt surface by a periodic pulsed reaction of a metal vapor jet had complex dynamics. An analysis of the experimental results indicated a considerable change in heat and mass transfer in the melt when three-dimensional vibrations were excited, compared with the processes that occur at q < 2 MW/cm2. Such changes enhanced the mixing of an alloying elements (compared with the familiar alloying methods) and established the optimal (for surface processing of metals) shape of a molten bath.