Improving the technological process of increas-ing the durability of the working tool of hydrau-lic hammers by detonation spraying

The development of modern technology places increasing demands on the performance of the hydraulic hammer parts. In a complex of problems of increasing their reliability and durability the question of wear resistance occupies a special place. Insufficient wear resistance limits the productivity of hydraulic hammers and their service life, increases the cost of repair and purchase of spare parts. Goal. The purpose of this work is to scientifically substantiate and experimentally confirm the effectiveness of strengthening the critical parts of the hydraulic hammer by detonation spraying. Methodology. Detonation spraying with hard alloy powder VK 25 (80 %) and the binder material PT-NA-01 (Ni 91 %, Al 9%) was performed on a cleaned surface without pre-treatment. VK 25 powder is a tungsten-cobalt carbide (WC-Co) containing up to 25% cobalt, and is used for work in conditions of fretting corrosion, abrasive wear at normal and elevated (up to 650 ° C) temperatures. A granular powder of 20 – 100 μm was used, which was melted in an oxygen-acetylene flame and gas flow and was transferred to the surface of the part. The thickness of the sprayed layer was 0.1 mm. The surface roughness of the parts before spraying was Ra 0.35–2.5. As a result of spraying, the roughness of the working surfaces of the parts increased to the values of Ra 4.8–5.4. Results. The composition of the coating based on tungsten carbide was chosen to strengthen the surface of the investigated parts by detonation spraying. Detonation spraying modes were selected. The conditions for hardening treatment were determined. The nature of damage to parts after detonation spraying was established. Originality To solve the problem of improving the performance of the working tool of hydraulic hammers, the use of the detonation method of coating was proposed. Practical value. The test results of the details strengthened by detonation spraying showed that the increase of wear resistance by 1,8 times in comparison with an initial variant was reached.

Influence of Detonation-Spraying Parameters on the Phase Composition and Tribological Properties of Al2O3 Coatings

Al2O3 coatings were applied on the surface of 12Ch18N10T steel by the detonation method at different degrees of filling of the detonation gun. The aim was to study the influence of technological parameters on the formation of the coating’s structure, phase composition and tribological characteristics. The degree of filling the gun with a gas mixture (C2H2/O2) varied from 53% to 68%. X-ray diffraction study showed that the content of α-Al2O3 increases depending on the degree of filling. The results showed that the hardness increases with an increase in the α-Al2O3 phase. When the gun is 53% filled with gas, the Al2O3-based coating has the hardness of 20.56 GPa compared to 58%, 63% and 68% fillings. Tribology tests have shown that the wear rate and friction coefficient of the coating is highly dependent on the degree of filling of the gun.

The influence of pulse-plasma treatment on the phase composition and hardness of Fe-TiB2-CrB2 coatings

This work are presented the research results of pulse plasma treatment influence on the phase composition, hardness, roughness and element composition of coatings on the bases of Fe-TiB2-CrB2. The Fe-TiB2-CrB2 coating was deposited by detonation method. The following pulse-plasma treatment was used to modify the structure and properties of the surface layers of the sprayed coating. The results of mechanical experiments showed that the hardness of Fe-TiB2-CrB2 coating increased after the treatment. On the basis of the X-ray analysis, it has been established that the increase of coating hardness is connected with phase transformations in a surface layer, in particular, with formation of oxide phases and increase of carbide particles quantity.

Alternative Ways To Study The Impact Of Ground Vibrations From Explosions On The Stability Of Buildings And Structures

The existing basic methods of studying the propagation of seismic-explosive waves in various mining-geological and morphological conditions to assess the impact of explosions on buildings and structures are briefly outlined. The results of studying the effect of the influence of the terrain on seismic vibrations during the passage of seismic explosive waves in them are presented. The issues of organizing experiments in full-scale field conditions, the time of which entirely depends on the time of drilling and blasting operations, are highlighted, which significantly slows down the stages of design, construction and operation of buildings and structures. Along with various explosions, as well as existing expensive installations and stands that create artificial vibrations for buildings and structures, it is offered detonation method for creating vibrations in the ground, both in design and construction, so and in the operation of buildings and structures. The detonation method proposed by the authors for creating artificial ground vibrations using a gas detonation unit makes it possible to simplify and accelerate the experiments and reduces labour and material costs.

MICRO-HARDNESS AND WEAR-RESISTANCE INVESTIGATION IN CARBO-METAL COATING COMPOSITES OBTAINED THROUGH GAS-DETONATION METHOD

The work purpose consists in the investigation of carbometal coatings wear-resistance and micro-hardness depending on chemical structure of their components. The investigation object is carbide-metal coatings. The result analysis of comparative wear-resistance tests witnesses that with micro-hardness increase in metal carbides of compositions: Cr3C2, WC, TiC, TiCN, at a constant content of cladding metal (30…35mass %), a value of wear decreases according to the linear law. Wear intensity of coatings of clad carbide mixtures with different materials is defined to a certain extent with wear intensity of material added to the matrix. In the course of the work there were developed coating compositions reinforced with quasi-crystals, there is defined an optimum composition and modes of coating application with the gas-detonation method and their wear-resistance and micro-hardness were investigated.

INFLUENCE OF STRUCTURAL-PHASE CONDITION ON THE MECHANICAL-TRI BOLOGICAL PROPERTIES OF Ti3SiC2 COATINGS OBTAINED BY THE DETONATION METHOD

The article provides the results of the research of the structure and properties of powder coatings based on titanium carbosilicide Ti3SiC2 obtained by detonation spraying on the surface of tool steel U9/У9 (equivalent to N9). Micro-indentation methods and abrasive wear tests for mechanical and tribological properties of Ti3SiC2 based coatings were conducted. The microstructure of the coating has a layered structure. The border between the coating and the base has a characteristic crinkled appearance. It was determined that the phase composition of the coatings changes during detonation spraying is a result of the decomposition of Ti3SiC2 powder into titanium carbide and titanium carbosilicide (secondary phases). Selected consolidation conditions ensure the formation of a Ti3SiC2/TiC composite material. The influence of the second phase content (TiC, TiO2) on the properties of coatings was studied. Studies of the microhardness of samples with coatings showed that, in the entire range of annealing temperatures, the microhardness of the Ti3SiC2/TiC composite material increases compared to the coating before annealing. It was found that the maximum microhardness of the Ti3SiC2/TiC composite material after annealing at a temperature of 800 ○C is explained by an increase in the content of the Ti3SiC2 phase. It was established that, during detonation spraying of Ti3SiC2 powders, a coating with a higher microhardness and wear resistance is formed.