Sergey N. Grigoriev

Optical Monitoring in Laser Cladding of Ti6Al4V

The TRUMPF 505 DMD machine with a 5-kW CO2 laser was used to enable scaling-up laser cladding (LC) to an industrial level. The aim of this study is to enhance product quality and to assure process stability and reproducibility by means of optical monitoring. Two originally developed pyrometers and an infrared camera FLIR Phoenix RDAS™ are employed in the LC of Ti6Al4V powder. The variations of brightness temperature versus laser power and cladding velocity are analyzed. A CCD camera-based diagnostic tool is applied for online monitoring of particle-in-flight velocity in coaxial powder injection.

Modification of the structure and properties of high-speed steel by combined vacuum-plasma treatment

Modification of the surface of a cutting tool from steel R6M5 by the method of vacuum-plasma treatment including ion nitriding in gas plasma and deposition of a wear-resistant (Ti, Al)N coating in the metal-gas plasma of vacuum-arc discharge is studied. Regular features of formation of nitrided layer are determined and optimization of its structure for various operating conditions of the cutting tool is performed. Modes of vacuum- arc treatment providing the lowest intensity of wear of the tool in the process of cutting are determined.

Vacuum-arc multilayer nanostructured TiN/Ti coatings: structure, stress state, properties

The effect of the conditions of deposition of vacuum-ac multilayer TiN/Ti coatings on their phase composition, structure, stress state and mechanical properties is investigated. Regular features of variation of the phase composition, structure-and-stress state and hardness as a function the value of the negative potential applied to the substrate during the deposition and on the thickness of the Ti and TiN layers in the multilayer coating are determined. The causes of the observed changes are analyzed using the mechanism of formation of surface layers of the vacuum-arc coatings under the conditions of the implantation processes stimulated by application of negative potential to the substrate.

Surface Defects Formation in Grinding of Silicon Nitride Ceramics

The effect of surface defects formation in grinding on two compositions of silicon nitride have been studied experimentally. The influence of composition of nitride ceramics, diamond wheels characteristics and grinding regimes on the grinding forces, final strength of samples and the degree of structure imperfection of their surfaces after grinding has been understood as a result of undertaken series of grinding tests.

Improving the Efficiency of the Cutting Tools Made of Mixed Ceramics by Applying Modifying Nanoscale Multilayered Coatings

The paper studies the influence of properties of a tool made of mixed ceramic by applying modifying with nanoscale multi-layered coatings on machinability of hardened tool steel XVG. The paper also examines the influence of cutting speed on wear resistance of mixed ceramic with nanoscale multilayered coatings. The mathematical models that found out the dependence of tool life of a ceramic tool with coating from cutting speed were developed.

Improving the Efficiency of the Cutting Tool Made of Ceramic when Machining Hardened Steel by Applying Nano-Dispersed Multi-Layered Coatings

The functional role of nano-dispersed multi-layered composite coatings (NMCC) deposited on the working surfaces of cutting inserts (CI) made of the layered high-strength ceramic (LHC) to equip the cutting tools when cutting hardened (high-strength) steels was investigated. It is shown that the variation in the composition, structure and properties of coatings allows controlling the contact processes at cutting, increasing the length of contact, reducing normal contact stresses and probability of micro- and macro-brittle failure of tool cutting edge. The mathematical models of cutting which establish dependences of flank wear land of the tool, the tangential component of cutting force, power of cutting and roughness of the machined surface from conditions of cutting of high-strengthen steels are developed. It is found out that the application of nano-dispersed ceramic multi-layered coatings on ceramic tool significantly increases its wear resistance and improves the quality of machining.

Nano-Scale Multi-Layered Coatings for Cutting Tools Generated Using Assisted Filtered Cathodic-Vacuum-Arc Deposition (AFCVAD)

The subject of this study were nano-nanoscale multilayer coatings formed using the process of filtered cathodic vacuum arc deposition in assisting high-energy ions of chromium. We used a special emitter (implantor) to generate chromium ions with high energy. Such key parameters of coatings as composition, structure, a thickness, hardness, adhesion in relation to a substrate obtained at various energy of chrome ions have been studied. It is establish the positive change of key properties of coating deposited on carbide inserts WC/CrC/Co, WC / (Co-Re), TiC/TaC/Co at assisted impact of ions Cr at ion acceleration voltage within the range of 10-40 kV. The results of measurement of parameters of coatings with use nanoindentometer are consistent with the X-ray analysis of the stresses in the coating (XSA study). The mechanisms of the effect of modified properties of coatings formed in assisting the filtered cathodic vacuum arc deposition on the properties of the carbide inserts in cutting structural steels and hard-to-cut nickel alloys have confirmed the high efficiency of the deposition process developed coatings and coating compositions.

Tool Life and Wear Mechanism of Coated Si3N4 Ceramic Tools in Turning Grey Cast Iron

This paper presents results of the investigation of Si3N4 ceramic inserts with CVD coatings in turning grey cast iron. The high effectiveness of Si3N4 ceramic inserts with multi-layered coating in the finish turning of the grey irons was shown. It was established that at the heart of the wear mechanism of coated Si3N4 ceramic inserts there is a chain of relations cutting conditions loading fracture of coating сhipping of ceramic surface layer failure of tools. One of the important features of wear mechanism of these tools is the operational defects formed at the coating substrate interface.

Parametric analysis of SLM using comprehensive optical monitoring

Purpose – This paper aims to propose methods for on-line monitoring and process quality assurance of Selective Laser Melting (SLM) technology as a competitive advantage to enhance its implementation into modern manufacturing industry. Design/methodology/approach – Monitoring of thermal emission from the laser impact zone was carried out by an originally developed pyrometer and a charge-coupled device (CCD) camera which were integrated with the optical system of the PHENIX PM-100 machine. Experiments are performed with variation of the basic process parameters such as powder layer thickness (0-120 μm), hatch distance (60-1,000 μm) and fabrication strategy (the so-called “one-zone” and “two-zone”). Findings – The pyrometer signal from the laser impact zone and the 2D temperature mapping from HAZ are rather sensible to variation of high-temperature phenomena during powder consolidation imposed by variation of the operational parameters. Research limitations/implications – Pyrometer measurements are in arbitr...

A STUDY OF THE QUALITY OF PREFORMS FROM IRON-BASE POWDERS PRODUCED BY FORMING COMBINED WITH SINTERING BY ELECTRIC CURRENT PULSES

Amethod and design of an installation for treating iron powders and making preforms for machine parts from them are described. In order to sinter a preform simultaneously with compressing the powder in a closed die pulses of eclectic current are passed through the powder. In accordance with the design of the multifactor experiment, the method is used to fabricate control specimens. Formulas are obtained for computing the relative strain due to upsetting until failure and the specific force of upsetting before failure using the results of measurement of the hardness of articles.