The paper presents the surface structure formation of AISI 304 stainless steel using the MiniMarker2-20A4 laser system. Austenitic steel was in the form of a cold-rolled sheet and a tape of increased strength for parts and structures. The article reviews the corrosion-resistant steel surface condition after analyzing the influence of power, frequency and speed of the laser and evaluates the impact on the corrosion resistance of the treated surface. The contrast assessment shows the treated structure effect on the alloy surface reflectivity. The calculations of the most optimal marking are made for obtaining the greatest contrast. The maximum contrast obtained as a result of parameter optimization was 0.83 and was improved by 10%. The article also touches on the influence and susceptibility to corrosion of stainless steel samples with laser marking by QR codes. This point displays structural change of the processed area and presentations steel surface structure AISI 304 after corrosion tests.

The results of the development of the flux CaO-Li2CO3-B2O3, operating in the oxidizing environment of the furnace, are shown. Flux is used to protect the melt from oxidation and removal of oxides from the coated sample surface. The use of this flux in open furnaces made it possible to apply high-quality nickel coatings with a thickness of 18 μm, which is comparable to the thickness of coatings obtained in vacuum furnaces in argon atmosphere. The negative effect of flux components on the sample surface was noted during prolonged contact under the conditions of the oxidizing environment of the furnace. Practical application of the research results will provide high-quality diffusion coatings on metal products. In addition, economic efficiency is maintained through accessibility of the equipment and flux components.

Laser marking of products and details is used more and more wide in different production areas, because it has undisputable advantages in comparison with other marking methods. Action of laser beam on the surface of marking product is the principal feature of laser marking. It is accompanied with local heating of this surface and its partial melting together with material evaporation from the surface contact point. Influence of laser impulse action on efficiency of marking on the surface of machine-building details is examined in this work. The samples of 08Kh18N10 steel were used as material. Marking was conducted by the system "MiniMarker 2-20A4", QR code was used as a marker. The marking parameters were optimized via the method of experimental design. The optimal marking procedure for getting maximal contrast of QR code was calculated and experimentally confirmed. Steel surface roughness was analyzed using profilograms. Contrasting effect and roughness of code were determined and relationship between these parameters was revealed. Contrast effect of marking increases with elevation of roughness. However, roughness has less input in increase of contrast effect comparing with colour hue of the surface of an information block and substrate. The link between surface roughness and contrast effect of marking is shown. Possibility of contrast effect assessment of QR code using profilometer is suggested.

This work shows readability of the QR code of the structural alloy Ti2 surface after the thermal influence. The main goal is the readability estimation after exposure to temperatures exceeding operating alloy temperatures and in destruction crash conditions. Contrast and readability were measured by using a Samsung smartphone and the program Adobe Photoshop CC 2017. The graphs of contrast change depending on the heating temperature were drawn. These graphs illustrate that significant changes in contrast are observed in the range from 500 to 600°C due to darkening of the base metal and the substrate, as well as fading of the dark elements of the code.

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