For solving the problem of improving the powder coatings modified by nanostructure components obtained by induction surfacing method tribological characteristics it is necessary to study the kinetics of the powdered layer melting and define the minimum time of melting.
For powdered layer predetermined temperature maintenance at sintering mode stage it is required to determine the temperature difference through blank thickness of the for one hundred-day of the define the warm-up swing on of the stocking up by solving the thermal conductivity stationary problem for quill (hollow) cylinder with internal heat source. Herewith, since in practice thickness of the cylinder wall is much less then its diameter and the temperature difference is comparatively small, the thermal conductivity dependence upon the temperature can be treated as negligible.
As it was shown by our previous studies, in the induction heating process under powdered material centrifugal surfacing (i.e. before achieving the melting temperature) the temperature distribution in powdered layer thickness may be considered even. Hereinafter, considering the blank part induction heating process quasi-stationarity under Fо big values, it is possible to consider its internal surface heating as developing with constant velocity.
There is unlimited hollow cylinder at the temperature T0=Tm (Tm is a powder melting temperature). The cylinder external surface temperature increases linearly. Melted layer with thickness R–η = ξ, where η is a distance from axis of the cylinder to the layer boundary, is formed beginning from the cylinder surface.
1 – melted zone; 2 – not melted zone; 3 – blank.
Fig 1 – a boundary conditions under centrifugal induction surfacing.
As a result of development the melting front movement mathematical model in a powdered material with nanostructure modifiers the minimum surfacing time is defined. It allows to minimize negative impact of thermal influence on formation of applied coating structure, to raise productivity of the process, to lower power inputs and to ensure saving of nonferrous and high alloys by reducing the allowance for machining.
The difference of developed mathematical model of melting front movement from previously known is that the surface temperature from which the heat transfer occures is a variable.
