Cathodic Cage Plasma Nitriding: An Innovative Technique

R R M De Sousa,C Alves,A De S Brandim,F O De Araújo,J A P Da Costa,R A De Brito

doi:10.1155/2012/385963

R R M De Sousa, C Alves + Show 4 more

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https://doi.org/10.1155/2012/385963

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Abstract

Cylindrical samples of AISI 1020, AISI 316, and AISI 420 steels, with different heights, were simultaneously treated by a new technique of ionic nitriding, entitled cathodic cage plasma nitriding (CCPN), in order to evaluate the efficiency of this technique to produce nitrided layers with better properties compared with those obtained using conventional ionic nitriding technique. This method is able to eliminate the edge effect in the samples, promoting a better uniformity of temperature, and consequently, a smaller variation of the thickness/height relation can be obtained. The compound layers were characterized by X-ray diffraction, optical microscopy, and microhardness test profile. The results were compared with the properties of samples obtained with the conventional nitriding, for the three steel types. It was verified that samples treated by CCPN process presented, at the same temperature, a better uniformity in the thickness and absence of the edge effect.

Highlights

Conventional plasma nitriding has been employed a lot in the industry, due to several advantages in relation to other nitriding processes, such as higher gas economy and smaller processing time, since the diffusion velocity of nitrogen (N2) in plasma nitriding is higher [1]
This fact is a consequence of the uniform temperature characteristic in this process, since in cathodic cage plasma nitriding (CCPN) technique there are no thermal gradients between the surfaces of the sample and sample holder
A small gradient is verified in the variation of the thickness of the layers nitrided by the new technique as function of the height of the samples, especially for higher treatment temperatures (773 K), where the maximum variation observed in the thickness is of the order of 10%, unlikely for samples treated by conventional nitriding technique the nitriding layer thickness variation was of the order of 25% between two successive sample heights value

Summary

Introduction

Conventional plasma nitriding has been employed a lot in the industry, due to several advantages in relation to other nitriding processes (gas nitriding and salt bath nitriding), such as higher gas economy and smaller processing time, since the diffusion velocity of nitrogen (N2) in plasma nitriding is higher [1] This process is used to improve superficial properties like hardness, wear, and corrosion resistances, in order to increase the useful life of nitrided components. A new plasma nitriding technique entitled cathodic cage plasma nitriding (CCPN) based on multiple hollow cathode effects is used and the results compared with the conventional plasma nitriding This technique presents some advantages compared to the conventional method, including process efficiency and the production of layers with uniform thickness. The temperature inside the nitriding chamber is uniform, and the thermal gradient is very small [5]

Experimental

Results and Discussion

Conclusions