The results of microstructural studies, the microhardness distribution, and the estimation of abrasive wear resistance of structural 30KhGSA steel samples hardened during continuous irradiation with a multichannel (48 beams) CO 2 laser are presented. Fine martensite forms in the hardened zone and the steel has a high hardness and abrasion resistance.

Metallographic studies and tests for abrasive wear resistance are performed for a Ni – Cr – B – Si coating obtained by laser powder cladding with the help of a multichannel (40 beams) CO 2 laser. Efficiency of repeated laser recrystallization of the surface layers of the coating is demonstrated. This treatment can be used to form structures with different values of dendritic parameter and affects positively the wear resistance of the coating. The wear characteristics are shown to depend linearly on the dendritic parameter, which may be used as a criterion of wear resistance of coatings.

The structure formation in corrosion-resistant steel during laser melting is studied. The results of investigation of the morphology and the granulometric and chemical compositions of a CL20ES steel powder, which was prepared by melt dispersion with a high-pressure inert gas, are reported. It is shown that samples characterized by the highest density and microhardness are prepared using a converging laser beam.

This paper presents experimental studies of the microstructure, phase composition, microhardness distribution, estimation of abrasive wear resistance of rapid steel, grade R6M5, after laser melting and subsequent tempering. A multichannel (40 beams) CO2 laser was used to process the steel. It has been demonstrated that improved abrasive wear resistance is achieved after laser melt quenching and short-term tempering at 560°C.

The regularities of the formation of the surface micromorphology and structure in stainless steel prepared via the selective laser melting of CL20ES powder are investigated. It is demonstrated that samples with optimal microgeometric characteristics possess the largest values of the density and microhardness and a low level of imperfection.

A metalloceramic NiCrBSiFe-WC coating on structural steel 40Kh was prepared by the method of laser cladding. The cladding was performed using a multichannel continuous CO2 laser radiation using the complex of ALTKU3 model produced by LLC "Centre of laser technologies", the city of Vladimir. The complex includes a multichannel (40 rays) CO2 laser with the output power of 3 kW and a technological stand with five coordinates for ray manipulation and with two ones for manipulation of the piece under processing. The prepared samples were examined metallographically. It is shown that at optimal modes a practically pore-free coating is formed with a minimal penetration into the base ensuring metallurgical fusion. According to the X-ray spectral microanalysis data the chemical composition is practically the same as that of the raw powder. In particular, the content of iron in the granules and in the matrix is nearly the same (about 4...5%). Due to the automatization of the processing by crossed rollers the sample surface after cladding is nearly flat and only requires a slight machining. The thickness of the cladding layer is about 700 gm in one pass. No cracks in the plane of the sample were observed. The weld junction demonstrates the same structure lengthwise thus indicating a high uniformity of the heat input during the cladding. The size of the thermal effect zone in the substrate is about 450 mu m. The laser cladding of the highly alloyed powder of the system NiCrBSiFe-WC onto the structural steel by means of the multichannel CO2 laser makes it possible to obtain a high-quality wear-proof coating since, in contrast to single ray lasers, it provides a high uniformity of integral heat input in the processing zone.

Studies are carried out on the microstructure and micro-hardness distribution of structural steel 30HN3. samples hardened by laser quenching by means of continuous radiation from a multi-channel 48 rays CO2 laser system CLT-Yu-5. To provide the formation of a uniform structure, hardness and depth distribution in the hardened material layer a laser emitter was used with four plug-in radiating tubes arranged one into another in an octahedral configuration (patent RF No 2580350). An important role of a high uniformity of the integral heat input across the hardening zone width on the uniformity of properties of the hardened layer is demonstrated. It was found that in the hardened area a finely dispersed martensite structure was formed. The carbides contained in the initial structure of sorbite dissolve not completely during laser hardening. They are characterized by a globular form and size of 0.2 ... 0.3 mu m. The microhardness of steel in the hardened area was about 6800 MPa. The thickness variation of the hardened layer, which is characterized by the ratio between minimal, h(min), and maximal, h(max), depths, is equal to 0.76 at h(max) = 1050 mu m. A reduction in microhardness in a tempering zone formed between two successive hardened bands down to the values of 5500 ... 6000 MPa was found. The width of this tempering zone is about 1.8 mm. The decrease of microhardness in this zone is due to a dissociation of the martensite and formation of tempering troostite structure. Lamellar carbides are formed during this process. Steel in the laser hardened area has a favorable structure in terms of the strength and durability. Thus, hardening of steel by means of multi-channel CO2 laser systems provides wide opportunities in improving of material properties and is recommended for hardening of expensive machine parts increasing their service lifetime.

The results of experimental studies into the surface micromorphology, microstructure, and microhardness of deposited P2M8 high-speed steel subjected to gas-laser cutting are presented. It is demonstrated that, in the area of laser action, the volume wear rate of high-speed steel is three times lower as compared to standard strengthening by means of volume hardening and triple tempering.