CS249917B1 - A method of directly forming a TiAb layer in the titanium surface layer and its alloys - Google Patents

Abstract

The essence of the method of forming a protective diffusion layer of TiAb on titanium and its alloys in a vacuum, which increases the resistance of the substrate to corrosion and abrasion at elevated temperatures, consists in heating a substrate of titanium or its alloys with an Al layer in an ion plating device to a temperature in the range of 600 to 660 °C, and in doing so, the substrate is further treated with ions in a glow discharge of an inert gas, the substrate being the cathode of this glow discharge at an argon pressure in the range of 10'2 to 102 Pa for at least 1 hour. This method makes it possible to form a diffusion layer of TiAb or TiAb + Al during the process of forming an Al layer on a titanium substrate without the need for subsequent diffusion annealing outside the vacuum chamber, which is particularly advantageous in terms of energy saving and the possibility of regulating the composition of the diffusion layer across its cross section.

Description

249917

The invention relates to a method of forming a surface-resistant layer resistant to corrosion and abrasion of high temperatures. The titanium and its alloys currently used do not meet the requirements for high temperature corrosion resistance in the entire application range, so their utility properties are adjusted by additional surface treatments such as galvanic or alumina coatings, nitriding and the like. In order to obtain adhesion and to form a diffusion layer, the treated components must be subsequently treated and annealed, which has an adverse effect on the mechanical properties of the base material. In addition, the process is burdensome, energy intensive and costly.

A further method of protecting titanium and its alloys at high temperatures is to form an aluminum layer on their surface in a vacuum of one of the known methods for forming coatings and subsequent diffusion annealing in a conventional furnace for heat treatment in a protective atmosphere. In this way, an intermetallic refractory and abrasion-resistant layer A1A3 can be formed on the surface of the substrate. A disadvantage of this method is that, after the aluminum layer has been formed with a nitrate substrate, it is necessary to subject the substrate to the above-mentioned additional diffusion annealing outside the vacuum chamber, which leads both to an increase in the energy intensity of the process and to that, in the case of diffusion annealing, the entire aluminum layer is formed into TiAh and it is difficult to diffuse the refractory layer composition after its cross-section.

These disadvantages are eliminated by the direct formation of TiAl3 layer on the titanium and its compounds according to the invention, the fact that the titanium substrate or its alloys is heated by the Al layer in the ion plating apparatus to a temperature of between 600 and 660 degrees Celsius, thus that the Al layer-forming substrate is further treated with ions in a more inert gas discharge, wherein the substrate is the cathode of this gaseous discharge of argon at a rate of 10 to 102 Pa for at least 1 hour. In this way, a TiAl3 substrate having a structural properties that can be influenced by changing the partial pressure of the inert gas is formed on the substrate by a current density on the substrate and at the rate of evaporation of the aluminum. The advantage of this method over the aforementioned method in which the conversion of Al to TiAh occurs after the additional diffusion annealing outside the vacuum chamber is that in one process, TiAh occurs in the vacuum chamber without the need to interrupt the process, which is time-consuming. energy advantageous as well as modifying the composition of the layer after its cross-section, for example TiAl 3 ++ A1. Further, as shown in Example 2, the process of forming the TiAl3 layer of the mosaic is such that a TiAh layer of thin thickness is first formed, to which the Al layer is formed in the vacuum. Since this process occurs in one process, without venting the vacuum chamber, there is no possibility of forming an anti-diffusion barrier on the surface substrate. This fact, together with the TiAh's proven property and the fact that the TiAh AI is not much higher than Ti in Ti, provides the ability to form a TiAh layer even at lower temperatures than 600 ° C in less time.

According to the invention, diffusion layers are formed on the titanium and its alloys from the TiAh intermetallic compound, optionally TiAh + Al, whose microhardness is 11,000 to 15,000 N. mm'‘z. The layers thus formed reduce the coefficient of friction by 400% and titanium wear by up to 800% by comparison with titanium compounds. Corrosion tests at high temperatures have revealed that the TiAh layer long-term resists oxidation in air at temperatures up to 900 ° C. EXAMPLES Example 1

The method of forming a TiAh layer on the titanium or its alloys according to the invention is characterized by the formation of an Al layer on the sublayer in an ionic cladding device of 10 < 10 > Pa, the substrate forming a base. Prior to the evaporation of Al by the electron beam at its power of 2 kW, so-called as well as o-heating of the substrate in the Ar discharge occurs. Ar is admitted through the inlet valve to the vacuum chamber at a pressure of 3 Pa. After reaching this pressure, a negative voltage of 2.5 kV is set to the negative substrate in the next step, compared to a grounded vacuum chamber. Through the regulation of napatiana substrate, the given parameters produce such discharge conditions in Ar (current value 0.1 to 3.0 mA.cnr2) to degas the substrate surface for 30 minutes, then remove thin layers from the surface of the substrate. xid films, while the substrate is heated to about 600 ° C. Due to the method of pre-treatment of the substrate surface in the vacuum chamber prior to evaporation of Al and also that its surface is bombarded with ionized Ar particles during the growth of Al, the conditions for microdiffusion of AI into the substrate are formed, thereby forming a Ti-Al and Al intermetallic compound layer. The commonly required thickness of the layer thus formed is approximately 10 μΐη, with a TiA layer thickness of approximately 3 μm, the remainder being Al. Example 2 In the second example, conditions

Claims (1)

249917 ky forming a TiAb layer on titanium or its alloys. The process of purifying the substrate in Ar discharge is consistent with the conditions set forth in Example 1. The difference is that initially 2 kW of Al layer of approximately 3 µm thickness is vaporized with an electron beam to such a cleaned surface of the substrate. Next, the Al-layer substrate surface is exposed to bombarded Ar particles in a vacuum coil at a pressure of 3 Pa and a negative tension of 2.5 kV for at least 20 minutes. This results in the dedusting of the Al layer from the surface of the substrate and at the same time the heating of the substrate to a temperature above 600 ° C, thereby creating conditions for the Al layer remaining to diffuse into the surface of the substrate to form a T1A3 layer. In the next step, the vaporized Al is electron beam assisted at its power of 2 kW and at a pressure of 10 mbar, followed by diffusion of Al through the TiAl4 layer to the substrate surface where it reacts with Ti to TiAlS. The above-mentioned properties of the T1A1 layers predetermine the use of Ti-based or surface-treated alloys, for example in Florida, seawater and also structurally bonding with Al without the risk of a so-called titanium weld at elevated operating temperatures as well as moving mechanisms. An example of a textile machine may be mentioned. Because of the accelerating or braking force, it is important that the weight of the barbell is as low as possible. Therefore, Al or Mg alloys are used to produce the Chinese. In some cases, these alloys do not have sufficient strength and, as an additional construction material, Ti and its alloys are considered. However, they are highly susceptible to seizure and therefore their surface needs to be adjusted. One of the ways to reduce the susceptibility of Ti and its alloys is its surface treatment according to the invention. SUBSTITUTE A method of directly forming a TiAb layer in the titanium surface layer and its alloys, characterized in that a titanium or tantane alloy substrate and an aluminum layer which has been prepared on the surface of the substrate in an ionic cladding system are destroyed. pressure from 10-2 to 102 Pa, immediately after the preparation of the aluminum layer, a plasma formed by an inert gas pressure ranging from 10-2 to 10 2 Pa in the ionic cladding device for at least 1 hour at the substrate temperature of 600 to 660 ° C.