Effect of Hydrogen on Processes of Reactive Diffusion in a 'Metal - Protective Coating' System

摘要

Theoretical and experimental investigation of the hydrogen influence upon activation energy of creation and migration of vacancies in Nickel have been carried out. On the base of obtained results the effect of intensification of self-diffusion in hydrogenated metal was found. The influence of treatment on hetero-diffusion kinetics during diffusion welding of different metals have been studied. Hydrogen is shown to enhance hetero-diffusion rate due to reduction of activation energy of the process. The velocity of reactive diffusion was studied on the base of investigation of phase-structural transformation of metal-coating system as result of thermal treatment in vacuum and hydrogen environments under temperature in the range of 773-1273 K. Diffusion coatings and gas-thermal coatings on the base of Ti, as well as complex electrochemical coating (CEC) on the base of Ni-B system deposited on 12Crl8Ni10Ti austenitic stainless steel and ARMCO-iron have been investigated. It should be noted that almost all physical-mechanical properties of metal-coating system are determined by microstructure of boundary zone and depend upon physical nature and volume content of phases formed near the metal-coating interface. The investigation of hydrogen influence on reactive diffusion in above mentioned systems show that this process connected with kinetics of forming and disintegration of substitutional and interstitial phases was highly enhanced by hydrogenation. This fact was confirmed with disintegration of intermetallic (Fe_2Ti) phases and borides (Ni_3B) as well as forming of carbides (Fe_3C) and hydrides (TiH_2) which was not found after treatment in vacuum environment. Obtained results could be explained in term of intensification of diffusion process in hydrogenated metals due to weakening of interatomic bonds. By the optimization of conditions of hydrogen treatment, the gas-thermal coating adhesion with substrates was increased by a factor of three and coating density by a factor of two. Structure control by hydrogen treatment and boron balls boring depth leads to enhancement of strength and wear-resistant properties of CEC Ni-B. The correlation between reactive diffusion and hydrogen permeability of the metal-coating system was established.