JPS5839773A - Surface hardening method for ferrous metal and its alloy - Google Patents

Abstract

PURPOSE:To harden the surfaces of steel contg. metals such as Ni, Co and others in which N, B are difficult to penetrate by forming thin layers of Ce, Cs, etc. on said surface and using the same as catalysts. CONSTITUTION:In hardening the surfaces of steel contg. Ni and Co such as stainless steel and high speed steel by penetrating B and N therein, thin layers are formed on the surfaces of the steel by the vapor of Ce or Cs and the steel is put in a vacuum furnace. While the steel is heated to high temp. together with boron or boron compd., gaseous ammonia is introduced into the furnace. The boron compd. is reduced by the gaseous ammonia and penetrates in the surfaces of the steel with the Ce and Cs layers as catalysts, thus forming the hardened layer of high abrasion resistance contg. boron nitride as a lubricant.

Description

[Detailed description of the invention] What are the conventional iron-based metals cobalt and nickel?

It was difficult to penetrate nitrogen-boron.

The present invention is based on the discovery that nitrogen and boron can be permeated by utilizing the fact that cesium, cerium, etc. are metals that have vapor pressure at low temperatures and are used as catalysts.

In practice, the following is required for surface hardening of steel materials.

(1) High surface hardness (2) Toughness so that the hardened part does not peel off (
3) It should be wear resistant (4) There should be little dimensional change from before treatment (5) The base material should not be weakened by hardening treatment.

The present invention was invented to meet the above conditions. That is, for the purpose of (1), since nitriding alone causes softening when exposed to high temperatures after treatment, boron was infiltrated at the same time. In conventional boronizing treatment, it did not penetrate unless heated to a high temperature, but in the present invention, it penetrates into the surface of a single item.

Vapors such as cesium and cerium are deposited to form a thin layer that acts as a catalyst.

In addition, in conventional borening treatment, due to the high temperature, a brittle compound is formed on the outermost surface by combining with iron and peeling off, so (2)
I can't satisfy you.

In the case of iron alloys, if nitrogen is permeated at a temperature of around 5oO<0>C to create an austenitic structure near the 2nd surface, it becomes easier to infiltrate. In addition, the action of cesium, cerium, etc. not only aids in borons, but also prevents the formation of brittle iron and boron compounds, and forms boron nitride on the outermost surface. It is a lubricant and is said to be better than tripden disulfide at temperatures above 400°C. Therefore, (3) is satisfied.

In nickel/cobalt and their alloys.

In the case of an austenitic structure at room temperature, by increasing the treatment temperature to increase the amount of cesium, cerium, etc. deposited and strengthening the catalytic action, it becomes possible to penetrate boron φ nitrogen, which was previously difficult to do. . Regarding (4),
It is no different from nitriding, but in the case of conventional nitriding, a nitride that easily peels off is formed on the outermost surface, but in the case of the present invention.

Due to the action of cesium, cerium, etc., nitrides that are easy to peel off are not formed, so there is no need to perform a diffusion treatment after nitriding.

Regarding (5), there is no need to worry about weakening the base material.

Another advantage of the present invention is that when a part of the mold is exposed to high temperatures after treatment, as in the case of a Guicast mold, it becomes an austenitic structure at a temperature of 400°C or higher because it contains nitrogen as a solid solution. There are no cleavage planes like in the case of ferrite structure, so you don't have to worry about it breaking into 90s, and even if hair tangles or cracks occur.

It is characterized by slow crack growth.

Also, metals such as cesium and cerium, which have a vapor pressure at low temperatures, form a solid solution with nitrogen and boron.

It has the effect of properly diffusing cesium and cerium into iron-based metals, so vapors such as cesium and cerium can enter powder metallurgy products and grain boundaries that have holes or holes that can only be seen under a microscope, causing catalyst damage. It is thought that the action causes nitrogen and boron to form a solid solution while producing boron nitride, which progresses in the direction of crystallization.

An example is the one of first order.

Example 1 Put the carbide tool (KIO) into a stainless steel box.

Put powdered sodium borohydride and cerium pieces in it, put it in a vacuum furnace, and make mercury column 10III11.
After creating a vacuum above and heating to 700°C ± 20°C, ammonia gas is introduced, heated for about 3 hours, and then cooled in the furnace.

Example 2 Hardened and tempered high-speed steel (8KH9) was placed in a stainless steel box and mixed with boron oxide powder and MEC.
・Insert a rod of metal (40% cerium, 60% other metals) with a diameter of 2 degrees, put this box in a vacuum furnace, create a vacuum of more than 10-4 kg of mercury, and raise the temperature to 450 degrees Celsius. , ammonia gas was passed through the mixture, and the mixture was heated for 3 hours and cooled in the furnace.

Example 3 A mold material 8KD61 was put in a stainless steel box, and boron oxide powder and MEC/metal powder were put in it, and it was put in a vacuum furnace to a vacuum of IQn- or higher and heated at 500°C ± 20°C.
After about 7 hours, cool with oil.

As described above, the present invention is particularly effective in improving the technology of tools and molds.

that's all

Claims (1)

[Claims] In vacuum at a temperature below the Al transformation point of iron. A thin layer of metals such as cesium and cerium is created on the surface of iron-based metals and their alloys, and this is used as a catalyst to reduce boron or boride with ammonia gas, and at the same time, surface hardening allows boron and nitrogen to penetrate. Law.