CS217645B1 - Wear-resistant method of applying titanium carbide or titanium carbonitride coatings to hard-alloyed products - Google Patents

Abstract

The invention relates to chemical-thermal treatment of metals and alloys, which is used in mechanical engineering and metalworking in order to increase the service life of metal products, in particular to a method of applying coatings of titanium carbide or titanium carbonitride to products made of sintered hard alloys. The essence of the invention lies in the fact that in the subject method according to the invention, the said products are treated in a closed space under a pressure of 133.10_2 to 133 Pa and at a temperature of 1100 to 1250 ° C. First, the products are treated with carbon dioxide gas, then titanium chlorides, which are obtained by the action of carbon tetrachloride on a titanium agent introduced into the closed space simultaneously with the products, after which the products are again treated with carbon dioxide or nitrogen gas.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the chemical-thermal treatment of metals and alloys used in mechanical engineering and metalworking to increase the durability of metal products, and more particularly to a method of applying titanium carbide or titanium carbonitride coatings to sintered hard alloy products.

The invention consists in the fact that in the present method of the invention regulate such products in an enclosed space at a pressure 133.10_ ^2-133 Pa at a temperature of 1100-1250 ° C. First, the products are treated with carbon gas, then titanium chlorides, which are obtained by the action of carbon tetrachloride on the titanium reagent introduced into the enclosure at the same time as the products, after which the products are again treated with carbon or nitrogen gas.

217B4S

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the chemical-thermal treatment of metals and alloys used in mechanical engineering and metalworking to enhance the durability of articles, in particular a method of applying wear-resistant titanium carbide or titanium carbonitride coatings to sintered hard alloy products.

The invention can be used by plants and companies producing hard alloy products as well as engineering plants using hard alloys as tools for machining metals and alloys.

Methods of depositing coatings of titanium carbide (Swiss Patent No. 332 328) and titanium carbide or titanium carbonitride (Austrian Patent No. 312 951) are known. They consist of the separation of said compounds from a gaseous medium consisting of titanium tetrachloride, hydrogen, methane or methane and nitrogen at temperatures of 900 to 1100 ° C under continuous flow of said gaseous mixture through a heated muffle furnace with articles. About four liters of titanium tetrachloride, 800 to 1000 liters of methane or nitrogen, more than ten cubic meters of pure and dried hydrogen are consumed in this process. The processes require careful cleaning and drying of hydrogen and other gases, as well as the use of bulky equipment to neutralize the reaction products (about 3 kg of titanium chloride and hydrochloric acid in a single process). These processes can only be carried out on special equipment which has been developed and built for this purpose, which requires considerable investment, and is intended exclusively for tantalum-containing hard alloys, which are much more expensive than tantalum-free alloys.

The known methods cannot ensure the production of coatings of titanium carbide or titanium carbonitride with maximum stecliiometry and without admixture of oxygen and hydrogen, and consequently also pirovous maximum viability of the articles with these coatings.

SUMMARY OF THE INVENTION The object of the present invention is to provide a process for the production of titanium carbide or titanium carbonitride coatings on sintered hard alloy products by means of a series of controllable operations, guaranteeing maximum enhancement of the product performance. waste products.

The above object has been achieved by applying a wear-resistant coating of titanium carbide or titanium carbonitride to hard alloy products based on the use of titanium chlorides, carbon gas, nitrogen gas, which consists in treating said products in an enclosed space at a pressure of ¹ to 100 mbar and at a temperature of 1100 to 1250 ° C first with carbon gas, then with titanium chlorides obtained by the action of carbon tetrachloride on the titanium reagent introduced with the products into said enclosure, and then with carbon or nitrogen gas.

By allowing control of the carbon content of the article prior to and in the coating and the absence of hydrogen and titanium tetrachloride containing oxygen and moisture, the method of the invention allows coatings of wear resistant titanium carbide and titanium carbonitride with stoichiometric ratios close to one and minimum. oxygen content.

The process for producing titanium carbide coatings or titanium kia / ribiotnitiride resistant to the measures is carried out according to the invention as follows.

The vacuum induction furnace is charged with treated articles, for example multi-faced insert, titanium reagent, for example titanium chips or titanium powder. In the cold state, the furnace is evacuated to a pressure of 1.33 Pa to 133.10 ^-2 Pa to ensure a minimum residual oxygen content. Then the heating is switched on and the temperature rises to 1100 to 1200 ° C with the pumps still working, depending on the hard alloy composition. Lower temperatures reduce process performance, while higher temperatures due to melting of the cobalt phase of the hard alloy are impermissible. When the temperature in this range is reached, a carbonaceous gas such as methane, propane, butane is introduced into the furnace and the product is carburized. The carburization delay time is selected according to the hard alloy composition and temperature. After ukofnče | nJauhličlovací the operation 'to the furnace space again evacuated to a pressure of 1.33 Pa to 133.10 Pa ^-2 IA introduced into a furnace with carbon tetrachloride. At the selected process temperature, it dissociates to form atomic chlorine.

The resulting chlorine reacts with the titanium reagent according to the following equations:

Ti + Clz -> TiClz

Ti + 3 Cl 2 -> 2 TiCl 2

Ti + 2 Cl 2 -> TiCl 4.

The lower titanium chlorides react with the carbon dissolved in the cobalt phase of the hard alloy to form a titanium carbide coating according to the following reactions:

TiCl 2 + C -> TiC + 2 TiCl 2

TiCb + C - TiC + 3 TiCb

Higher titanium tetrachloride TiCl 2 reacts with the titanium reagent to form lower chlorides again and the process proceeds in a closed cycle. The pressure rises to 66 to 133 Pa. The thickness of the titanium carbide coating formed is controlled by the residence time, which depends on the temperature selected.

After the coating of the selected thickness has been produced on the product, a carbon or nitrogen gas such as methane, propane, butane, nitrogen, ammonia is introduced into the furnace and the process temperature is maintained for some time to increase the stoichiometric ratio of titanium carbide or

1 conversion of carbide to carbonitride. After holding, the heating is switched off, the products are cooled together with the furnace and removed from the furnace.

The furnace used in the method of applying wear resistant coatings can be used simultaneously as a furnace for sintering products or for other purposes for which it is intended.

The developed method increases the durability of hard alloy inserts with mechanical attachment 2.5 to 5 times, requiring no special equipment, large investments for implementation, use of explosive hydrogen, equipment for its purification and drying as well as equipment for neutralizing waste products. The method can be used to apply coatings on hard alloys of various brands comprising a carbon-dissolving binder.

In order to better understand the present invention, specific examples are set forth below.

Example 1

A titanium carbide coating is applied to the multi-faceted, hard alloy alloy insert, consisting of 14 wt. TiC, 8 wt. C10 and 78 wt. WC.

The products and the titanium powder are placed in a vacuum induction furnace. The furnace chamber is evacuated to a pressure of 1.33 Pa and switches on the heating. Vacuum pumps operate continuously during heating. When the temperature reaches 1120 to 1150 ° C, the pumps are switched off, methane is introduced into the furnace and held for two hours.

After the carburizing of the platelet surface is completed, a vacuum of 0.8 Pa is generated in the furnace, the pumps are turned off and carbon tetrachloride is introduced into the furnace. A titanium carbide coating with a thickness of 7 to 10 µm is formed on the surface of the plates within two hours at a pressure of 0.8 to 66 Pa. Methane is then introduced into the furnace. Within two hours, the titanium carbide coating was additionally carburized and the carbide composition approached the stoichiometric composition. After the operation is completed, the heating is switched off and the furnace is cooled. A titanium carbide coating having a thickness of 7 to 10 μπι is obtained. Stoichiometry: TiCo _i97 .

Machining time for steel with Birinellia 2 hardness ^! 079 N / mm ² at a cutting speed of 140 m / min, a cutting depth of 1 mm, a feed of 0.2 mm / rev was 11.4 for uncoated inserts

645 min. at a wear of the back surface of 0.8 mm, for plates having a coating obtained according to the invention of 31.9 min. when the back surface is worn 0.45 mm. The durability factor is more than 2.7 with considerably less wear.

Example 2

A carbonitride coating is applied to the 10-wt. % (TiC + TaC), 8 wt. Co and 72 wt. WC. The process was carried out analogously to Example 1. The furnace chamber was evacuated to a pressure of 1.33. IO ^-2 Pa. Carburization is carried out in an environment of propane at a temperature of 1140 to 1160 ° C for one hour.

The platelets are treated with titanium chlorides for three hours. During this time a titanium carbide coating of 10 to 12 μΐη is formed on the top of the plates. Nitrogen is then introduced into the furnace and held for three hours. During this time, a 10-12 m thick titanium carbonitride coating and TiCN composition is formed on the surface of the plates.

The plates are tested in analogy to Example 1. The durability factor is 2.8 at a wear of 0.25 mm.

Example 3

A titanium carbonitride coating is applied to a multi-faceted, hard alloy alloy insert, consisting of 92% by weight. WC and 8 o / o What.

The process was carried out analogously to Example 1. The furnace chamber was evacuated to a pressure of 0.133 Pa. Carburization is carried out in a methane environment at a temperature of 1200 to 1250 ° C for one hour. The platelets are treated with titanium tetrachlorides at a pressure of 0.133-133 Pa for three hours. During this time, a titanium carbide coating with a thickness of 5 to 7 μια is formed on the surface of the plates. Ammonia is then introduced into the furnace and held for three hours. During this time, a titanium carbonitride coating with a thickness of 5 to 7 μτη, a composition of TiCN, is formed on the surface of the plates.

Plates with the obtained coating exhibit a durability factor of 2.5 at a wear of 0.5 mm when machining pig iron.

Claims (1)

Subject A method of applying wear-resistant titanium carbide or titanium carbonitride coatings to sintered hard alloy products by using titanium chlorides, carbon gas, nitrogen gas, characterized in that said products are treated in a confined space at a pressure of 133. IO ^{- 2} to VYNALEZU 133 Pa and a temperature of 1100 to 1250 ° C first with carbon gas, then with titanium chlorides, which are obtained by the action of carbon tetrachloride on the titanium reagent introduced with the products into the confined space, and then with carbon or nitrogen gas.