Different laser processing methods used to modify the surface properties of materials are discussed. Metallographical (optical, SEM, TEM), microprobe, x-ray diffraction, wear resistance and microhardness investigations of 3Cr (0.26%C/3.11%Cr/1.98%Mn/0.5%Mo), 10Cr (0,20%C/9,85%Cr/1.0%Mn/0.5%Al) T15 high-speed tool steel, and ductile cast iron surface treated by a continuous CO₂ (with different power), Nd-YAG and ruby pulsed lasers radiation, are presented as an illustration showing the benefits of laser application in modification of material properties. In addition laser alloying of 0.30% carbon plain steel with tungsten is also described.

Microstructure modification by laser remelting or laser alloying was studied on carbon Ck45 and high speed steels. Laser remelting of Ck45 by overlapping laser tracks led to a great refinement of martensitic structure, especially in the heat affected zone of subsequent laser track. High speed steel (HSS) M2 after laser remelting showed, beside the tetragonal martensite, the diffraction lines of cubic carbides of the M₆C and M₁₂C types. Laser alloying of M2 HSS using vanadium carbide (VC) additions caused increasing of eutectic in the interdendritic space, which was accompanied with reduction of the M₆C and rising of the MC. M2 HSS laser alloyed with molybdenum carbide (Mo₂C) showed formation of the M₆C for the hipereutectic compositions while at the highest concentrations of molybdenum, primary dendrites of the M₂C and stabilized ferrite were stated. High additions of borides: CrB or VB₂; developed formation of the primary borides of blocky type containing a high amount of W, Cr or W, V, respectively. Laser alloying of Ck45 by means of: CrB, VB₂ and B₄C showed: in the case of CrB an eutectic (alpha) '/M₃(C,B)/M₂B as well as primary precipitates of the M₂B phase for hipereutectic compositions; by adding VB₂, the M₃B₂ and M₂B phases were identified experimentally for hipereutectic concentrations; for alloying using B₄C, the cellular dendritic structure together with primary borides of the (tau) -M₂₃(C,B)₆ phase were stated for hipereutectic compositions. The phase diagrams of M2 HSS + (VC or Mo₂C) as well as Ck45 + B₄C systems were calculated to predict changes of the constitutions due to laser alloying. Comparison of the solidification structures established experimentally with the calculated phase diagrams revealed a good correlation for the carbides, especially.

Constructional steels of A441, 4340 and 15B28H AISI types were laser remelted and laser alloyed using VC or CrB. The applied laser remelting rised already the Rockwell hardness to 50 - 60 HRC when the laser alloying by means of VC or CrB to about 75 HRC. The maximum of hardness was usually located in the center of the laser alloyed tracks. A strong microstructure refinement was observed in all cases of modification. Rising of the austenite amount was stated in the examined steels subjected to the VC or CrB laser alloying. The VC and M₃C phases were established by the VC laser alloying when the M₃(C,B) and M₂B phase were identified by application of CrB laser alloying for lower and higher concentrations of alloying additions, respectively. The residual stresses of tension type were stated in the center of the laser remelted tracks and the level of which was diminished by laser alloying.

The work deals with selected problems of modification of metal surface layer parameters, which parameters are significant for the use of these metals in electrical engineering. The first part of the paper is devoted to selected questions of technology of metal surface layer properties, based on the doping of these layers with foreign elements. The second part of the work contains selected results of the authors' own studies. Special attention has been paid to the modification of resistivity and microhardness of surface layers.

The paper deals with an evaluation of homogeneity of laser modified surface layer of martensitic steel grade 21H12NMFA. The authors trying to find an optimum values of control parameters of high power laser machine with beam of which the surface layer of specimens was modified. As the examination of layer homogeneity a nondestructive electromagnetic method has been chosen. For verification purpose of the method the microhardness measurements were applied. In both cases the results of measurements made it possible to reconstruct the surface layer and to visualize it with computer color mapping on base of which the homogeneity of the layer was evaluated. As an example the evaluation procedure was applied to two specimens, namely No 14 for which an optimal parameters of laser treatment were achieved and No 15 which found to be in the center of Kiefer's optimization plan.

For a CO₂ laser irradiation of the steel samples kept at liquid nitrogen (LN₂) temperature of 77 K the transparence window of LN₂ below 0.3 eV is utilized. The irradiation effects are analyzed by means of microstructure observations and by the measurements of microhardness and are compared with results obtained for the reference samples of the same material under standard gas shielding conditions. A marked reduction of the heat affected zone for the LN₂ case in comparison with that obtained for the reference samples is observed. Microphotographs indicate on a decrease of the grain size dimensions in the remelted and heat affected zones, and especially in the intermediate layers between them. The finer structure of increased homogeneity results in an extension of the surface layer of higher microhardness.

General description of verification tests of a system to give treatment to internal surfaces of small-sized cylindrical guides with the multimode beam of the CO₂ laser of 800 (W) power has been followed with preliminary findings effected.

The processing of laser hardening has been discussed. Paper presents a comparison of microstructure and mechanical properties (hardness and wear resistance) of three grades of carbon steels containing 0.15, 0.45 and 0.9% C after conventional and CO₂ laser hardening by melting and rapid solidification. Laser hardening of examined steels resulted in higher hardness and better wear resistance in comparison with conventional hardening. Post laser treatment tempering effected in carbides precipitation and further improvement in hardness and wear resistance.

Preliminary results of investigating the processes of the CO₂ laser-beam treatment of the thin-walled blades of disk cutters have been discussed in the paper. What has been included in the study is the data on practice of applying such treatment to disk cutters, in particular on: (1) processes of hardening the starting material, (2) parameters of exposures to laser-beam emissions, (3) selected parameters of grinding the laser-treated cutters. Moreover, some information on additional tooling used with this technology to exposures and to grind laser-treated disks has been included, as well.

The paper presents the results of analysis of thermocapillary phenomena in the liquid phase of a laser fusion. Making use of the FIDAP program the authors modelled the phenomena of convection using silver as an example. Silver was subjected to the action of a laser radiation pulse of the duration (tau) equals 4 ms and the Gaussian distribution of the power density q_o approximately 10⁹ . . . 10¹¹ W/m², of the radius r_o equals 150 micrometer. The axis symmetry of the model was assumed. Thermal coefficients were assumed to be constant for each phase, while the values of the surface tension as a function of temperature. With such assumptions the Marangoni convection is the primary cause of convection motion. The velocity field and the shape of the interfacial surface were determined on the basis of calculations performed using the FIDAP program. The shape coefficient (K equals d/h - width by depth) of the fusion is in good agreement with the real value. The paper indicates some possibilities of using a model built with the help of the FIDAP program for predicting some results of laser melting.

The paper deals with stresses induced in the alloyed layers of high-melting metals in the laser treatment process with a continuous beam and a pulse of a duration (tau) equals 4 ms. It has been found that the threshold power densities of laser radiation resulting in the permanent plastic strain of the metal under treatment are greater than the ones used during treatment. Making use of an analysis of the temperature field, the cooling rates of the treated zone have been determined by the finite difference method and an analytical method. The spatial non-uniformity of the heating and cooling rate of tungsten and molybdenum can be the cause of plastic strain and fractures on the metal surface. Experimental investigations were carried out for the optimal parameters of a laser radiation beam (the maximum depth of the alloyed layer, possibly with the smallest number of fractures). A privileged direction of fractures at an angle of 45 degrees in relation to the direction of scanning was observed (basing on the microscopic observations of 2 mm by 2 mm layers made on the surface of 10 specimens). Experiments showed a considerable effect of the type of the metals treated on the likelihood of occurrence of fractures; these are distinct and numerous in the case of molybdenum alloyed with nickel, whereas they cannot be observed in tungsten alloyed with nickel at a magnification of X 20,000. The smaller concentration of stresses in tungsten is also confirmed by the results of microhardness measurements (Table 2). The different behavior of the metals under treatment may be caused by volumetric changes brought about by metallurgical phase transitions.

The paper examines the influence of laser remelting of Al₂O₃-Ni and Al₂O₃-Ni+CrAl ceramic layers spread on creep-resisting alloy by plasma-spray processing, upon the quality of ceramic coatings which are the thermal barrier and high temperature corrosion protection of these alloys. It has been stated that laser beam scanning of 0.103 X 10⁹ W/m² power density ensures good quality of coatings at the beam shift rate equal 1 - 2 m/min. At smaller scanning rate, laser remelted ceramic layer spalls and chips. The examination of corrosion resistance in the medium of sulphur compounds has been carried out on plasma-sprayed samples which underwent chromoaluminizing and laser remelting. Diffusive chromoaluminizing and laser beam remelting proved advantageous for corrosion resistance of the alloy. An alloy without coating and with coating but without additional chromoaluminizing showed very low corrosion resistance in the medium of sulphur compounds.

Process parameters of the lser stereolithography by means of metal powder sintering are experimentally investigated for the bronze B10, Fe-Cr and Al-Ni alloys, pure Sn, and Cu. The multilaye structures ae prepared trace-on-trace by remelting of the previously deposited mela powder under the cw CO₂ laser irradiation in an Ar flow environment. Severl trces of a hiehght of 0.1 - 0.9 mm connected via fusion zones are produced for each samle which results inan efficient formautlion f avolumetric structures of dimensins usfficient for microanalysis ndconsiderationof th emultlayer goemtry. For th beam intensities of about 10⁵ W/cm² and smaple feeding rates of 0.8 - 1.8 m/min th fusin zone thickness donot 4xceed several percent of th layer height. Rsutls indicate, that th epowderized Fe-Cr anAl-Ni alloys and also bronze B10 are well suited for a fast prorotyping due to th low porosity, homogeneous structure and good mechaniclpropetis acheivable.

In the paper the results of attempts at laser welding of amorphous ferromagnetic foils on the iron and cobalt base have been presented. The usefulness of this technology for making small magnetic circuits of metallic glass has been demonstrated. The action of laser radiation leading to rendering the structure amorphous and the infraction of a laser beam with an amorphous material have been discussed. Finally, the results of pulsed welding of a pack of amorphous foils and some properties of the welds formed have been discussed.

In the paper problems related to the use of laser pulsed welding in constructing pneumatic probes for measuring dynamics flows have been presented. A number of detailed technological problems solved for cases of welding miniature elements of probes have been discussed. Special requirements connected with particular operations of laser joining of elements of varied dimensions and different geometry have been shown. Successful instances have been presented of laser pulsed welding of five-hole probes, which considerably contributed to the miniaturization of sensors, which in turn allowed the measurement of infrasound and transonic flows.

In this paper a CuBr pulsed laser ((lambda) equals 510.6 nm and 578.2 nm) having an average output power of 10 W and efficiency (2,5%) is presented. Owing to a considerably lower operating temperature (560 degrees Celsius) CuBr laser becomes an alternative for more widely used conventional Cu laser (with operating temperature 1500 - 1600 degrees Celsius) in such applications where the required laser output power is lower than 50 W. Examples for such applications, mainly for high precision laser machining in electronic are presented in this paper.

The paper presents how to use the VIPS program for analyzing the image of magnetic domains present in transparent thin magnetic films. The domains' image is obtained in a measurement system using the Faraday effect. Application of the VIPS program allows you to automatize the research and laboratory and measurement work related to the domain structures.

An analysis of actual state of a view about pulsed laser deposition method, its applications and perspectives and also physical phenomena during laser deposition processing were presented.

The investigations of sandwich plates deformation generated by local thermal load acting on the face are presented. An experimental program is conducted to measure the displacements normal to the faces, value of thermal expansion coefficient of the foamed polyurethane core and displacements at the interfaces under different temperature increment. Holographic interferometry and speckle photography were used for displacement measurement. Special optical set-up is designed for local heating of the sandwich plate face using cw argon laser. Experimental results are found to be in good agreement with numerical calculation.

A marking method based on a multichannel rf excited CO₂ laser is presented. The method can be convenient in production processes in marking of identity numbers on manufactured elements.

The system of large-size elements quality diagnosis has been presented. Quality assessment criterions of controlled objects are based on measured shape and position deviations in selected area of an object. Quality assessment is presented in the form of relevant synthesized indexes: element errors function, global out-of- parallelness factor, harmonic indexes. In the case of assessment of complete basing or quiding unit the system enables correction of elements position. The described computer system controls any measurement units. Present version cooperates with the laser interferometer system which performs translational and rotational displacement measurements.