Thermal diffusion chromium plating of structural carbon steel 20 by high frequency currents

To increase the service life of the gear teeth made of steel 20, operating under high shock loads, their main surfaces were subjected to high-temperature diffusion metallization, namely, chromium plating with high-frequency currents. As a result of diffusion metallization, the surface hardness increased 5.1–5.4 times – from 156–159 HV to 800–866 HV, and the strength level 3.3 times – from 250 to 820 mAh. Optimal parameters for the diffusion metallization: current I = 0.25–0.3 kA, power Pe = 8–10 kW, hardening τ = 8–10 min. By the method of scanning electron microscopy, it was found that after diffusion saturation of the surface of the gear teeth with chromium, the steel has a homogeneous structure with clearly pronounced transition layers, the average thickness of the diffusion layer was 0.06 mm. Energy dispersive analysis showed that after diffusion metallization with chromium powder, the basic composition of the steel remained constant, only the qualitative ratio of the components changed. X-ray phase analysis revealed the presence of an αFe-phase with the incorporation of Cr on the surface of the sample.

Assessment of wear resistance of hardened additive products made of electroerosive cobalt-chromium powder

Experimental studies of the wear resistance of hardened additive products made of electroerosive cobaltchromium powder obtained in alcohol are carried out. With a friction path of 500 m, the following was established: partial wear of the counterbody and adhesion of wear products of the sample to the counterbody; the size of the wear track of the sample; the depth of the profile of the wear groove of the sample surface; friction coefficient; wear of a counterbody made of steel and a hardened sample made of a cobalt-chromium alloy. Keywords: electroerosive cobalt-chromium powder, additive product, hardening, wear resistance. [email protected]

Investigation of the Finishing Technology of SLM Implants

In this research, the use of plasma electrolytic polishing (PEP) as a finishing treatment of materials obtained by the SLM method from CoCr30 cobalt-chromium powder is proposed. To assess the possibility of using this method, a simulator sample was used. The imitation sample was polished for 60 seconds. The roughness and the size of the removal material were measured. Based on the results obtained for the simulator sample, a conclusion was made about the possibility of using PEP technology for finishing the treatment stent. The stent simulator was also polished. The processing time was 30s and 60s. The geometric parameters were measured, and the removal material was calculated. Images of the stent surface were taken before and after PEP. It was found that with an increase in the processing time from 30 to 60 seconds, the allowance removed from all surfaces increases almost twice. The possibility of using the PEP technology as a finishing operation for the manufacture of stents from cobalt-chromium alloys is shown.

Investigation of the structure and properties of reinforced additive products obtained from electroerosive cobalt-chromium powder

The analysis of the wear resistance characteristics of samples sintered from high-chromium electroerosive powders obtained in kerosene on a friction path of 500 m is performed. It was established experimentally that: there is a partial wear of the counterbody and the buildup of the products of wear of the sample on centralo; the magnitude of the wear track of the sample is 383,1 µm to 473,5 mm; the depth of the profile grooves of the wear surface of the sample is 5 microns; the coefficient of friction of the surface of the sample is from 0,228 to 0,826; the wear rate of the counterbody made of Stainless Steel AISI 420 and the sample made of sintered steel 12X17 are 0.016 and 1.138, respectively.

Influence of Chromium Concentration on Corrosion Resistance of Surface Layers of Stainless Steel

Phase transformations occurring during the non-vacuum electron-beam surfacing using a mixture of amorphous boron and chromium powder (from 5 to 30 wt%) as well as the effect of the resulting structure on the corrosion resistance of the surface layers of chromium-nickel austenitic steel have been investigated. It has been found that when processing a powder mixture with a minimum chromium content (5 and 10 wt%), layers with a dense arrangement of borides are formed. Further increase in chromium concentration (20 and 30 wt%) leads to the formation of solid solutions in the modified layer. It has been shown that an increase in the concentration of chromium in the surface layer leads to a twofold increase in the corrosion resistance of the 12Х18Н9T (AISI 302) steel surface.