Electrochimica Acta 50 (2005) 4538–4543
Properties of electrodeposited nanocrystalline Ni–B alloy films
K.H. Lee∗, D. Chang, S.C. Kwon
Surface Engineering Department, Korea Institute of Machinery and Materials, 66 Sangnam-dong, Changwon,
Gyeongnam 641-010, Korea
Received 7 January 2004; received in revised form 10 March 2004; accepted 10 March 2004
Available online 5 July 2005
Abstract
The influence of the boron content on the various properties of nanocrystalline Ni–B alloy produced by electrodeposition was investigated.
The considerable reduction in grain size was observed with increasing boron content. The internal stress was tensile and increased linearly
with increasing boron content. Hardness increased up to 750 Hv at 2 at.% boron and then kept the value to 11 at.% boron for as-plated Ni–B
coatings.
The hardness of Ni–B films increased considerably due to the intermetallic Ni3B precipitation by the heat treatment and maximum hardness
of each coating increases with boron content. Wear resistance decreased with increasing the boron content because of high friction coefficient
and brittle fracture of coating with high content of boron.
© 2005 Elsevier Ltd. All rights reserved.
Keywords: Nanocrystalline Ni–B alloys; Electrodeposition; Internal stress; Microhardness; Wear properties
1. Introduction
the solution. Ni–B alloys can be also obtained by electrode-
position using the above-mentioned reducing agents. The
plating process and maintenance of the solution is much
easier than that of electroless plating. Moreover, concen-
tration of boron in the deposit, which is related to physical,
mechanical and chemical properties of deposits, can be easily
controlled.
Since the studies on the electrodeposition of Ni–B alloys
are few, the deposition behavior and various properties of
electrodeposited Ni–B alloy are not sufficiently understood
yet. In this study, using differential scanning calorimetry
(DSC), X-ray diffraction and transmission electro micro-
scope (TEM), the composition of the electrodeposited Ni–B
films, structural features and phase transformations of Ni–B
beforeandafterheattreatment, andtheirrelationwithinternal
stress, microhardness and wear properties was investigated.
Many of nickel-base alloys have been developed and used
as viable chromium substitutes. Among them Ni–B alloys
have surface finish and wear properties similar to those of
chromium plating [1–4]. As-plated coatings have a hardness
of approximately 600–700 Hv, but annealing increases their
hardness. The maximum hardness of about 1200 Hv, which
is comparable to the hardness of chromium, occurred during
post-plating heat treatment [5,6].
Nanocrystalline or amorphous Ni–B films can be prepared
by electroless or electrochemical deposition. Electroless
deposition is performed by using strong reducing agents
such as borohydride, hydrazine borane, pyridine borane,
and dimethylamine borane. Electroless deposition runs at
high temperature (80–90 ◦C), high pH values (13–14). After
adding a reducing agent spontaneous decomposition with
precipitation of metallic nickel in the bulk of the solution
occurred. To avoid this, stabilizing agent is introduced into
2. Experimental
∗
Stainless steel (AISI 304) coupons with a size of
Corresponding author. Tel.: +82 55 280 3545; fax: +82 55 280 3599.
E-mail address: lgh1636@kmail.kimm.re.kr (K.H. Lee).
10 cm × 10 cm were used as substrates for electrodeposi-
0013-4686/$ – see front matter © 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.electacta.2004.03.067