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

Abstract

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.