日本金属学会誌

J. Japan Inst. Metals, Vol. 43, No. 12 (1979),
pp. 1115-1120

The Effect of NH3 Gas Addition to the Atmosphere on the Metallurgical Property of the Nitrided Layer Formed by Ion-nitriding and Ion-softnitriding

Mizuo Edamura1, Minoru Makimura1, Takashi Kajikawa1, K\=oichi Imai1, Satoshi Furuitsu1 and Satoru Kunise1

Engine and Motorcycle Group, Kawasaki Heavy Industries Ltd., Akashi

Abstract:

The study on the ion-nitriding (or ion-softnitriding) in the atmosphere of N2-H2 mixing gas (or N2-H2-C3H8 mixing gas) was previously carried out. In this report, NH3 gas was added to the above-mentioned atmosphere, and the degree of dissociation of NH3 gas, the thickness and composition of the compound layer and the depth of the diffusion zone were investigated (nitriding temperature: 550°C, nitriding time: 6 h, total gas pressure: 400 Pa (3 Torr), current density: 11.5 A/m2). The main results were as follows.
(1) The degrees of dissociation of NH3 gas as a function of its molar fraction in the introduced gases (NH3-N2-H2 and NH3-N2-H2-1%C3H8) were measured when the molar fraction ratio of N2 to H2 gases in the exhaust gases was kept constant as 1/3. Using the above measured degrees of dissociation of NH3 gas, the molar fractions of NH3, N2, H2 gases in the introduced gases (NH3-N2-H2 and NH3-N2-H2-1%C3H8) were well calculated to keep the molar fraction ratio of N2 to H2 gases in the exhaust gases as 2/1.
(2) When the molar fraction of NH3 gas in the exhaust gases was increased, the voltage was increased and the thickness of the compound layer was also increased; however, the depth of the diffusion zone was almost constant.
(3) The volume ratio of the ε -Fe2--3N phase to the sum of the ε -Fe2--3N and γ '-Fe4N phases in the compound layer, cε /(cε +cγ '), was almost constant when the molar fraction ratio of N2 to H2 gases in the exhaust gases and the C3H8 gas content were constant. Here cε and cγ ' were the volume fractions of the ε -Fe2--3N and γ '-Fe4N phases in the compound layer.


(Received 1978/10/13)

Keywords:


PDF(Free)PDF (Free)     Table of ContentsTable of Contents

Please do not copy without permission.