Diffusion chromising of magnetically soft alloy articles - using controlled heating and cooling rates to give improved magnetic properties and non porous coating

摘要

The method comprises surface chromising the articles in a powder mixt. at 800-1200 degrees C and cooling at a rate not exceeding that of recrystallisation and diffusion saturation, the cooling rate being close to that of diffusion transformations and formation of a magnetic structure. Pref. the heating rate is 200-400 degrees/hr. and the cooling rate is 20-200 degrees/hr. below the Curie point. Used esp. in the prodn. of parts of radio-electronic, relay and switching appts. of optical and mechanical and automations systems, e.g. for computer, aircraft and space equipment. The process comprises annealing the articles with provision of a protective coating, and increases the magnetic permeability, reduces the coercive force and magnetic ageing, and enhances corrosion resistance of the articles. The coating also provides the articles with increased wear resistance, is uniform and has low porosity and roughness.