Hardening of a quick-speed steel tool through nitration process with nitrogen controlled potential

The study of the gas nitriding method, which allows obtaining high-quality diffuse layers in high-speed steel P6M5 on the basis of an internal nitrogen hardening zone with no brittle nitride zone, has been viewed. Research results of phase composition of nitrided steel with a change in the nitrogen potential of the atmosphere during dilution of ammonia are presented. Nitrided tool increased resistance during drilling constructional steel and titanium alloy, which is due to precipitation hardening treatment of the internal nitrogenization zone using tungsten nitrides, is given.

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.

Technological tests of a multi-seat device for vibro-shock processing of long parts of complex shape

The article deals with the issues related to the possibility of ensuring the indicators of quality of long complex-shaped parts by using vibration-impact processing in the technological process of their manufacturing using a special multi-seat device. The analysis of the design of representatives of long parts and the requirements for the quality of their surface layer, as well as the operational properties, made it possible to formulate the basic requirements for the design of multi-seat tools and develop a prototype for technological tests. The device allows processing two fragments of long parts and was used to establish the possibility of processing full-sized products and to establish optimal processing modes. Elements of the helicopter spars, which have the most complex design in the class of the considered parts, were used as fragments. Particular attention is paid to the processing of the inner surface of a complex shape and variable cross-section. The test results showed the possibility of using a multi-seat device for vibration-impact hardening treatment, which ensures the achievement of the specified parameters of the surface layer: surface roughness and microhardness with high process productivity.

HEAT TREATMENT EFFECT ON MARAGING STEEL MANUFACTURED BY LASER POWDER BED FUSION TECHNOLOGY: MICROSTRUCTURE AND MECHANICAL PROPERTIES

Laser Powder Bed Fusion (L-PBF) is a widespread additive manufacturing technology in industrial applications, for metal components manufacturing. Maraging steel is a special class of Fe-Ni alloys, typically used in the aerospace and tooling sectors due to their good combination of mechanical strength and toughness. This work analyses the heat treatment effect on the microstructure and hardness value of 300-grade maraging steel manufactured by the L-PBF process. The considered heat treatment consists of a solution annealing treatment followed by quenching and ageing hardening treatment. The effect of ageing temperature is reported, in a wide temperature range. Results show that solution annealing treatment fully dissolves the solidification structure caused by the L-PBF process. Moreover, the ageing hardening treatment has a significant impact on the hardness, hence on strength, of L-PBF maraging steel. The optimal ageing conditions for the L-PBF maraging steel are identified and reported: in particular, results show that the hardness of 583 HV is achieved following ageing treatment at 490 °C for 6 hours. A higher treatment temperature leads to over-ageing resulting in a decrease of hardness. Conversely, an excessive ageing time does not seem to affect the hardness value, for the ageing temperature of 490 °C.

Research of Alternative Options for Strengthening Surface Treatment of Cast Iron Products

The article considers issues of increasing wear resistance of cast iron products by methods of thermochemical treatment of their surface layer. Methods are proposed to solve the problem of wear from cast iron of grade EN-JS1060 due to development of technological processes of strengthening treatment. Alternative versions of strengthening technologies are represented by nitrocarburizing, liquid nitriding and carbonitration. Results of examination of control samples at increasing loads after 200 N before catastrophic wear are given. Comparative analysis of these results showed that samples after carbonitration and liquid nitriding had the greatest bearing capacity (1000 N). Carbonitration is selected as a most preferred option of the surface hardening treatment. Non-poisonous cyanoacid salts are used to realize it.

Assessing efficiency of seed hardening treatments in blackgram

Seed is a biological entity and its quality is improved through seed hardening. Seed hardening is a simple method to alter the physiological and biochemical nature of the seeds. Any successful technology could be performed well in farmer field and their feedback will be helpful for fine tuning of the technology. On farm trial was conducted in farmers field with two seed hardening treatments viz., (i) Seed hardening with Zinc sulphate @ 0.1g/lit for 3 hr and (ii) Seed hardening with Sodium molybdate @ 0.5g/lit for 3 hr along with untreated seeds as a control during Rabi, 2017-18. The results revealed that seed hardening with Sodium molybdate @ 0.5g/lit performed better interms of yield (678 kg/ha), net return (Rs.23,125/ ha) and benefit cost ratio (1.81) compared to seed hardening with Zinc sulphate @ 0.1g/lit and control and which was 669 kg/ha, Rs.21913/ha, 1.77 and 514 kg/ha, Rs.12159 /ha, 1.45, respectively. However, the minimum yield difference was observed between the seed hardening treatments but both seed hardening treatment were excelled over the control. Hence, seed hardening with Sodium molybdate @ 0.5g/lit or Zinc sulphate @ 0.1g/lit for 3 hr found effective in increasing the yield in blackgram. The knowledge level of farmers on seed hardening treatments increased from 13 to 70 per cent which was made through on farm testing programme.

Increasing the durability of cylindrical parts of wheelcarms of railway

A description of a new design of a vibrating machine for strengthening the surface plastic deformation of cylindrical long parts, in particular stabilizers of wheeled carriages of railway cars, is given. The main design and technological parameters of the process of vibration – centrifugal strengthening of these parts are outlined. The influence of technological parameters of this hardening process on such basic indicator of hardening processing as depth of hardening is experimentally investigated on cylindrical samples from 45 steel. Mathematical dependences for the choice of optimal values of design and technological parameters of this hardening treatment are given. The list of long cylindrical parts for which vibration – centrifugal strengthening treatment is suitable and effective is outlined, among which torsion shafts of suspension of military tanks, axles of wheels of railway transport, drilling and casing pipes of gas and oil wells.

Influence of Nitriding Temperature on Mechanical and Tribological Properties of Titanium

One of the commonly used methods for the surface hardening treatment of pure titanium was nitriding. Based on the study of nitriding temperatures on the properties of the pure titanium, some conclusions can be drawn in this paper. The surface hardness of samples after nitriding was gradually increased firstly and then decreased with the processing temperature increasing. And the hardness of the diffusion layer reached the maximum value of 1792 HV when the processing temperature at 1050°C. At the same temperature, the indentation modulus also reached the maximum value of 270 GPa. The wear depth reached the minimum value at 1050°C. At different nitriding temperatures, the minimum of wear depth was 14.8 μm. In summary, when the processing temperature at 1050°C, the nitriding of pure titanium can improve the comprehensive properties.

Influence of Deep Rolling and Induction Hardening on Microstructure Evolution of Crankshaft Sections made from 38MnSiVS5 and 42CrMo4

In order to improve properties of complex automotive components, such as crankshafts, in an application-oriented way, several surface hardening treatments can be applied. Concerning the material performance the definition of adequate process parameters influences the resulting surface properties and, thus, the effectiveness of surface hardening treatments. To analyze most relevant process-microstructure-property relationships, the present paper reports results obtained by two different well-established surface hardening procedures, i. e. deep rolling as a mechanical treatment and induction hardening as a thermal treatment. For each hardening process widely used crankshaft steel grades, i. e. a medium carbon 38MnSiVS5 microalloyed steel and a quenched and tempered 42CrMo4 were selected and thoroughly characterized upon processing, using equal parameter settings. The results reveal that deep rolling in contrast to induction hardening proves to be a less sensitive surface layer treatment with regard to small differences in the initial microstructure, the chemical composition and the applied process parameters. Differences in microstructure evolution with respect to the applied surface hardening treatment are studied and discussed for the highly stressed fillet region of automotive crankshaft sections for all conditions. In this context, high-resolution SEM-based techniques such as EBSD and ECCI are proven to be very effective for fast qualitative evaluation of induced microstructural changes.