{'fraction_non_alphanumeric': 0.026843051631132802, 'fraction_numerical': 0.0165681993321346, 'mean_word_length': 4.5266146202980835, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Influence of technological parameters on the geometry of single-track laser clad nickel based alloy on grey cast iron substrate

On the example of glass forming equipment, the surfaces of which must have high wear resistance during repeated contacts with molten glass, a study was made of laser cladding of nickel based alloys on a substrate of gray cast iron. In study the shapes of individual tracks are investigated with varying laser radiation power, processing speed and powder feed rate. The influence of technological parameters on the width and height of the clad is shown. A similarity is found between the two principles of measuring the dilution through linear dimensions and the areas of track in cross section. A high correlation between dilution and laser radiation power over a wide range of speeds has been established, which has made it possible to develop a scheme of control laser cladding process with achieving a low level of dilution in order to minimize the heat effect zone (HAZ).


Introduction
In the manufacture of shaped glass products in large batches (millions of pieces), glass container manufacturers are faced with a problem associated with the permanent failure of the critical components of equipment. In the process of using the glass forming equipment, the details of glass molds operating under conditions of cyclic alternating thermomechanical loads and produced, in most cases, from cast iron, are subject to the greatest defectiveness. A significant influence on the stability of glass forming equipment is the desire of container manufacturers to reduce the mass of produced glass products (reducing the wall thickness), increase the rate of release of packaging, while improving the quality of melted glass [1,2].
One of the most promising technologies to improve the service life of glass forming tooling is to restore the working surfaces of wear-resistant, corrosion resistant and other coatings obtainable laser cladding a nickel-based powders. [3,4] The wide application of laser cladding is limited to the use of automated process control systems that do not have in their arsenal of algorithms for adjusting operation windows with changing geometric parameters of the deposited layer. This is caused by an insignificant share of research in the field of dependencies and regularities of the formation of the clad on the technological parameters of the processing time.
The aim of this work is to identify patterns of geometric characteristics of the tracks on the technological processing parameters for the creation of an automated process control system of laser cladding. In studies [5][6][7][8] on the assessment of the influence of technological parameters, the main characteristics of the clad were the height, width and shape of the clad, the depth of penetration, and the percentage of defects. Parameters of control were the laser radiation power, processing speed and powder feed rate.

Experimental
The experiments were carried out on an installation consisting of: a 6-axis Kuka HR 60LH robot, a Sulzer Metco Twin 10C powder feeder, ytterbium fiber laser YLS-6 (max. average power 6 kW), COAX powder nozzle.
The chemical composition used in the experiments of cast iron and surfacing powder Eutroloy 16233 (particle size 40-120 μm, initial hardness 31-36 HRC) was determined using a Bruker Q-8 Magellan spectrometer and is presented in tables 1 and 2. Deposition process was performed using a continuous laser radiation in inert gas (argon). The height of the deposited layer was significantly lower than the thickness of the substrate to ensure sufficient heat removal from the treatment zone.
Review papers [5][6][7][8] allowed to choose the following processing parameters: laser power P of 700 to 2800 W, the processing speed S from 9 to 18 mm/s, powder flow rate F of 12 to 25 g/min.
The clad height H [mm] is defined as the height of laser track over surrounding substrate, the clad width W [mm] is a distance between side points where the laser track touches and b is the clad depth representing the thickness of substrate melted during the cladding and added to the clad region. The clad area A c [mm 2 ] is the cross-section of the clad area above the surrounded substrate surface and the molten area A m [mm 2 ] is the cross-section molten area under the surrounded substrate surface. The area of defects were measered in the clad and melted areas and was determined as The measurements were carried out with the help of JMicroVision software on cross sections. Photographing of the microstructure was performed on an inverted microscope with magnification x25 on the Nikon Epiphot TME200.
Regression analysis and processing of experimental results are implemented in STATISTICS software [9].

Results and discussion
To evaluate the effect of laser radiation power P, processing speed S and powder flow F on geometric parameters, 32 clad tracks were manufactured. The results of measuring are shown in table 3.
With constant powder flow (F = 12 g/min), the height and width of the deposited layer were plotted against laser radiation power and processing speed (      As the processing speed increases (Figures 1 and 2). the width W and the height H of the clad decrease according to a linear relationship: the correlation coefficient R for W is from -0.94 to -0.99. and for H -from -0.89 to -0.99. but at a laser radiation power P = 2800 W there is a drop in height. especially noticeable at lower processing speeds (9 and 12 mm/s). It is caused by excess heat. which is expressed in a significant depth of penetration (from 0.737 to 0.905 mm) and lack of powder: the base metal is melted to great depths and feed powder fills the melt pool instead of forming effective deposited layer.
Increasing the power of the laser radiation causes linear increase (R from 0.94 to 0.97) of the track width ( figure 3). and the maximum track height for each speed is at a power level of 1400-2100 W with a peak at 2100 W (figure 4).  To evaluate the effect of powder flow on geometric parameters of clads prepared at different scanning speeds (9-18 mm/s) with a different powder flow (12-25 g/min) at constant power P = 2800 W for maximum deposition rate process. The cross-sections map of these clads are shown in figure 6. In this case. the effect of the scanning speed on the geometric parameters of clads is preserved: with its growth. the width. height of the track. dilution and effective area of clad decrease as well as at constant feed powder. The obtained dependences (figures 1-4. 7a. 7b) made it possible to confirm the existing regularities of the influence of technological parameters on the width and height of clad. but not enough to create a control system for the laser cladding process. To solve this problem. the effect of the technological parameters of laser cladding on the dilution. which is one of the indicators of the quality of the deposited layer. was analyzed.
Dilution b/(H+b). reflecting the ratio of the thickness of substrate that was melted during the cladding process h to the total melt height H+b.
This calculation is similar to the area ratio A m /(A c +A m ) of the melted base metal Am to the sum of the areas of the clad layer and the melted base metal (A c +A m ). since these ratios are almost identical for all tracks ( figure 8). This can be explained by the use source of a laser radiation with a Gaussian energy distribution and the use of a coaxial feed powder which results in a uniform melt pool relative to the laser beam axis (the laser beam in all experiments was directed along the normal to the substrate). The low dilution indicates a small penetration depth of the substrate. a decrease in the HAZ and the probability of defects in the clad. so it is more preferable.