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Enhanced activation of self-passivating metals

A self-passivation, metal technology, applied in the direction of metal material coating process, solid diffusion coating, coating, etc., can solve the problem of no claim, can not use stainless steel workpiece, surface area to surface area inconsistency and so on

Active Publication Date: 2020-12-04
SWAGELOK CO +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0020] However, it does not claim to be applicable to the self-activation technique described in the aforementioned publications of Somers et al. and Christiansen et al., where the workpiece is activated by contact with acetylene or "N / C compounds"
Rather, experience has shown that if stainless steel workpieces of complex shape are not surface treated by electropolishing, mechanical polishing, chemical etching, etc. Works, or even if it does, produces results that are spotty at best and inconsistent from surface area to surface area
So, as a practical matter, these self-activating surface hardening techniques cannot be used on complex shaped stainless steel workpieces unless these workpieces are pretreated to first remove their Beilby layer

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0078] A cut section (1 / 2 inch (1.27 cm) diameter) of a machined ferrule made of AISI 316 stainless steel was encapsulated with 10 g of guanidine hydrochloride in a degassed (1-2 Pa) 12 mm diameter glass ampoule (210 mm length). The ampoule was heated in a furnace at a rate of 50°K / min to 720°K (447°C), which evaporated the guanidine hydrochloride. After two hours at 720°K, the ampoule was removed from the furnace and rapidly cooled. Subsequent metallography of the cross-sectioned ferrule revealed diffusion to form a 37 μm deep carbonitride shell with a near-surface hardness of 1000 Vickers (25 g recess load).

Embodiment 2 and 3

[0080] Example 1 was repeated a second and a third time. In a second run, the shell depth was found to be 38 microns deep and the near surface hardness was 1300 Vickers. In a third run, the shell depth was found to be 36 μm and the near surface hardness was 1200 Vickers. These examples demonstrate that the technique of the present invention is highly reproducible.

Embodiment 4

[0082] Example 1 was repeated except that the workpiece (i.e., the cut portion of the machined ferrule) was treated with 0.01 g of NH 4 Cl and 0.11 g of urea were encapsulated, the glass ampoule was 220 mm long, and the ampoule was heated to 450° C. for 120 minutes. This example was run four times separately. The obtained nitrocarburized workpieces all exhibited a near-surface hardness of approximately 1200 Vickers hardness and uniform shell depths of 15 μm, 18 μm, 18 μm and 20 μm, respectively.

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Abstract

A workpiece made of a self-passivating metal and having one or more surface regions bounding a Beilby layer resulting from a prior metal forming operation obtained by exposing the workpiece to a heated oxygen-free nitrogen halide salt The generated vapor is activated for subsequent cryogenic gas hardening.

Description

Background technique [0001] Cross-Referenced Related Applications [0002] This application claims the benefit of earlier Provisional Patent Application Serial No. 62 / 031,338, filed July 31, 2014, the priority of which is hereby claimed, and the disclosure of which is incorporated herein by reference in its entirety. [0003] conventional carburizing [0004] Conventional (high temperature) carburizing is a widely used industrial process for increasing the surface hardness ("shell hardening") of shaped metal articles. In a typical commercial process, a workpiece is contacted with a carbon-containing gas at high temperature (eg, 1000° C. or higher), whereby carbon atoms released by decomposition of the gas diffuse into the surface of the workpiece. Hardening occurs by the reaction of these diffused carbon atoms with one or more metals in the workpiece, thereby forming distinct chemical compounds, namely, carbides, which then act as discrete, extremely hard crystalline particl...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C23C8/24C23C8/26C23C8/30
CPCC23C8/26C23C8/02C23C8/32C23C8/24C23C8/22
Inventor 皮特·C·威廉姆斯史蒂文·V·马克斯弗兰克·恩斯特安娜·V·阿加博努瓦
Owner SWAGELOK CO