RU2621750C2 - Method of forming a wear-resistant layer on the surface of a detail of titane or titanium alloy - Google Patents

Abstract

FIELD: machine engineering.

SUBSTANCE: method of forming a wear-resistant layer on the surface of parts made of titanium or alloys based on it involves carrying out the process by the method of electrospark doping in various modes, and a layer of a carbon-based material is applied to the workpiece surface of the hardened part, which, for adhesion to the surface of the part, is applied in the form paint or paste with a thickness of at least 0.01 mm.

EFFECT: invention provides the formation in the surface layer of a part of titanium or alloys based on it carbide and titanium nitride, increasing the hardness of the formed reinforced layer.

4 cl, 1 ex

Description

The invention relates to the field of engineering, and in particular to methods of forming coatings by methods of electrospark alloying.

The prior art methods for carrying out the process of electrospark alloying in various modes (SU 1609564 A, 11/30/1990; RU 95102608 A1, 12/10/1996). The disadvantage of these methods is to obtain coatings of small thickness (up to 0.12 mm) and not high enough quality.

The prior art method for electrospark alloying of parts based on iron-carbon alloys, in which graphite electrodes EG-2 are used as an anode electrode (G. Ivanov, Technology of electrospark hardening of tools and machine parts. 2nd ed., Revised and supplemented. M .: MASHGIZ, 1963 .-- 304 p.). The disadvantage of this method is the formation in the hardened surface of iron carbides with relatively low hardness, compared with carbides of elements such as titanium, vanadium and chromium.

The prior art method for electrospark alloying, in which a nanostructured alloy of the composition of tungsten carbide-cobalt in the ratio of 3 ÷ 25 wt.% Is used as a hardening electrode (electrode-anode). cobalt with a grain size of tungsten carbide of 2 ÷ 120 nm (RF Patent No. 2371520, 10.27.2009). The disadvantage of this method is the insignificant thickness of the hardened layer.

The prior art method of forming a wear-resistant coating on parts made of titanium or a titanium alloy, including the formation of a coating by the spark method using a graphite electrode cooled by gaseous nitrogen as an anode (RF Patent No. 2349432, 03.20.2009). The disadvantage of this method is the use as a carbon-containing material of only a graphite electrode and the use of nitrogen gas as a cooling medium.

The closest in technical essence is the method of applying wear-resistant coatings to the surface of parts made of titanium or titanium alloy, including applying a layer of powdered graphite to the surface of the workpiece by friction coating and subsequent conduct of electrospark alloying at various processing modes (Boytsov A.G. et al. Surface hardening parts by combined methods. M.: Mechanical Engineering, 1991). The disadvantage of this method is the use as a carbon-containing material of only powdered graphite, the use of friction spreading to fix the powdered graphite to the surface of the part.

All this reduces the versatility of the method.

The proposed method is more versatile in relation to the prototype.

The increase in versatility is expressed in the possibility of forming a wear-resistant layer on the surface of parts made of titanium or alloys based on it using materials based on carbon, which are previously applied in the form of paints or pastes on the surface of the workpiece.

The method is as follows.

The coating layer of carbon-based materials is preliminarily applied in the form of paint or paste with a layer of at least 0.01 mm onto the surface of the part made of titanium or an alloy based on it required for forming a wear-resistant coating. A layer of less than 0.01 mm is technically difficult to apply evenly. Spark alloying occurs due to the interaction of carbon from the coating with titanium (the material of the part) by the SHS mechanism, which initiates a spark discharge, which results in the formation of titanium carbide and titanium nitride in the surface layer of the part, which increases the hardness of the hardened layer. To prevent overheating of the part due to significant heat generated during the process, the method provides for the organization of cooling by feeding into the contact zone of the anode electrode and the part of a non-combustible gas (or gas mixture) or non-flammable (non-combustible) liquid. The method of supply is selected from the conditions of availability — blowing, spraying, wetting, etc. To form a hardened layer containing other phases along with titanium carbide and nitride, the method involves the use of any electrically conductive material as an anode. The use of copper and alloys based on it as an anode electrode makes it possible to additionally alloy the surface layer with copper, which increases its ductility. The use of ferroalloys as an anode electrode allows the formation of a surface layer containing, along with titanium carbide and nitride, other phases: the use of ferrochrome contributes to the appearance of additional chromium carbides and nitrides in the hardened layer, and ferroboron additionally forms iron borides in the hardened surface layer.

Since the process of electrospark alloying is carried out by the SHS mechanism, which initiates a spark discharge, the process can be carried out in various modes and installations of electrospark alloying.

Example. As a hardened part, a VT5 titanium alloy tube with a diameter of 22 mm and a wall thickness of 2 mm was used. A paste containing soot (elemental carbon) was applied to the outer surface with a layer of 0.5-0.8 mm. A copper electrode was used as the anode electrode. Hardening was performed on an EFI-46A installation in various modes (open circuit voltage 15–190 V, short circuit current 3.5–4.5 A). The hardened surface layer contained, along with carbide, nitride and titanium carbonitride, copper. The hardness of the layer was 71-72 HRC, the depth of the layer was in the range of 1.0-1.5 mm.

Claims (4)

1. A method of forming a wear-resistant layer on the surface of parts made of titanium or alloys based on it, including carrying out the process by the method of electrospark alloying in various modes, characterized in that a carbon-based material in the form of paint or paste is not previously applied to the surface of the hardened part in the form of a paint or paste less than 0.01 mm. 2. The method according to p. 1, characterized in that a non-combustible gas or a non-combustible mixture of gases is supplied into the contact zone of the anode and the workpiece. 3. The method according to claim 1, characterized in that a non-flammable liquid is supplied to the contact zone of the anode and the workpiece. 4. The method according to p. 1, characterized in that the anode is any conductive material.