Development Of A Small Instrument Applied In Electrospark Surface Strengthening And Experimental Research

Electrospark surface strengthening method has simple equipment and easyoperation, low cost advantages, and can be used for strengthening the surface of thesteam turbine blades, turbine blades and mechanical parts and repairing the wear parts,to improve the surface hardness, wear resistance and corrosion resistance, and theservice life of the parts can be improved in several times. In this article, for the seriousabrasion problem of the turbine flow components, a surface strengthening equipmentconvenient for site operation is developed, and the research on Electrospark surfacestrengthening with stainless steel0Cr13Ni5Mo is carried out.Aiming at the problem that discharging process is not stable, and dischargingenergy is uneven existed in traditional vibration electrode type Electrospark surfacestrengthening equipment, the original circuit of traditional equipment is improved. Anon-contact switch formed by SCR and SSR are added in the circuit based on thesequential control charging and discharging process to make the spark discharge in thepulse signal control in an orderly way. And it uses rotating electrode and argonprotection system, remarkably raising the stability of the working process and achievesa higher strengthen quality.Three different electrode materials are used to strengthen the stainless steel0Cr13Ni5Mo samples, and the organization characteristics, the elements distributionand the phase structure of the strengthening layer are analyzed. The results show that,in the process of strengthening, the electrode materials and substrate material mutualinfiltration and melting element diffusion, new phase structure are formed in thestrengthening layer, and the strengthening layer is metallurgical combination. Nanoindentation experiments show that the hardness and elastic modulus value of thestrengthening layer are significantly improved, the hardness gradually reducing alongthe depth direction. The difference of restitution coefficient between the strengtheninglayer and the base is not big, show that they are combined good.The wear resistance of the strengthening layer is studied, and the wear mechanismis analyzes. The wear resistance of the strengthening layer made up by differentelectrode materials are evaluated systemically from three aspects as the frictioncoefficient, the worn surfaces and wear quantity. The results show that thestrengthening layer using YG8electrode materials has the best wear resistance. Theinfluence of process parameters on the wear resistance of strengthening layer isdetailed analyzed, the effects of the electro-parameters，strengthening time and flux ofargon gas are obtained, the wear resistance of the strengthening layer made up atworking voltage of80V, capacitance240μF, strengthening time2min/cm~2, flux of argon gas5L/min is the best.Based on the electrochemical measurement technique and the electrochemicalimpedance spectroscopy test method, the electrochemical corrosion properties ofstrengthening layer is studied, and the results indicate that in the corroding liquor, thecorrosion potential increases, and the corrosion current density decreases, the corrosionspeed slow down, corrosion resistance improves performance. Using impedancespectral data, the equivalent circuit of the process that can simulate the corrosionprocess is obtained. Through the analysis of the surface porous resistance and thecharge transfer resistance changes, we know the corrosion products can jam the pore inthe strengthening layer and play a pole in delaying corrosion in a certain stage.