RU1836484C - Method of application of nitride layers on parts made of titanium and titanium alloys - Google Patents

Abstract

An economical method for applying nitride layers to titanium and titanium alloys. In a short time, layer thicknesses of 20 mu m are achieved by nitriding under pressure in an ammonia atmosphere. Temperatures of 500 to 1000 DEG C and pressures of 0.2 to 10 Mpa are required for this purpose.

Description

The invention relates to methods for depositing nitride layers on parts of titanium and titanium alloys by thermochemical treatment of parts with ammonia or a gas mixture containing ammonia, under pressure and at a temperature above 500 ° C.

Titanium as a structural material has some advantages over steel: lower specific gravity, corrosion resistance and increased tensile strength. These advantages are opposed by a relatively low hardness, which necessitates surface treatment if wear resistance is to be increased. Typically, such a surface treatment consists in applying layers consisting of titanium carbide or titanium nitride. In known methods of nitriding parts from titanium and from titanium alloys, the treatment was carried out by means of high-energy ga &

call or through electromagnetic fields. These methods are very expensive and can only be used with simple geometry of the workpieces.

The aim of the invention was the creation of such a method of applying nitride layers on parts made of titanium and titanium alloys by thermochemical processing of parts in ammonia or in a gas mixture containing ammonia, under pressure and at a temperature above 500 ° C, which would provide moderate costs and the possibility of obtaining layers with a thickness of 20 microns or more in relatively short periods of time.

This problem is solved due to the fact that the treatment is carried out at a temperature of 500-1000 ° C and at a pressure of 0.2-10 MPa, and the partial pressure of ammonia is at least 0.2 MPa.

The temperature in the range of 700–950 ° C ft dw00 turned out to be especially expedient

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a pressure in the range of 0.5-7 MPa, moreover, a partial pressure of ammonia of at least 0.2 MPa is required,

With this method, under pressure on parts made of titanium and titanium alloys having any geometry and dimensions, with the appropriate dimensions of chamber furnaces, it is possible to obtain sufficiently thick coatings of nitride layers (up to 20 microns or more). Of exceptional importance is the fact that gases with a high degree of frequency are not required; it is sufficient to use ammonia of ordinary industrial quality. In addition, it is possible to mix nitrogen with ammonia, wherein only a partial ammonia pressure of at least 0.2 MPa is required for the nitriding process.

The thickness of the applied titanium nitride layer over a wide pressure range depends on the temperature and on the processing time. The surface is glossy gold and its hardness is substantially increased. At pressures in the range above 6 MPa, the layer thickness is almost independent of pressure.

The drawing shows the dependence of the thickness of the titanium nitride layer on parts of pure titanium on the pressure and temperature of the atmosphere containing ammonia.

Already at a temperature of, for example, 500 ° C and at an absolute pressure of 2 MPa (20 bar), after 1 h, it is possible to obtain a titanium nitride layer thickness of 10 μm. At a temperature of 880 ° C, a layer of pure titanium nitride with a thickness of 20 µm is applied over the same period.

At a pressure of 6 MPa (60 bar), for example, a titanium nitride layer with a thickness of 30 µm is formed if the samples are kept for 1 hour at a temperature of 880 ° C.

With a further increase in pressure

up to 9 MPa (90 bar), the effect of pressure on the thickness of the nitride layer is reduced. The increment is no longer linear. At higher pressures due to

of the rapid formation of dense nitride layers, only nitrogen diffusion through the deposited layer determines the time factor.

Similarly to pure titanium, titanium alloys can also be nitrided, for example

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An autoclave is not required for the application of such coatings, and processing can be carried out in a conventional chamber furnace.

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Formula of the invention

1, A method of applying nitride layers to parts of titanium and its alloys, comprising nitriding at elevated pressure in an atmosphere of nitrogen-containing gas at a temperature above 500 ° C, characterized in that the process is conducted in an atmosphere of ammonia or a gas mixture containing ammonia and nitrogen at a temperature 500 ° C ° C, a pressure of 0.2-10 MPa, with a partial ammonia pressure of at least 0.2 MPa.

2. The method of claim 1, on the basis of which the process is conducted at 700-950 ° C and a pressure of 0.5-7 MPa.

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