Prakt. Met. Sonderband 46 (2014) 265 
ı Werkstoffen. LOW-PRESSURE VACUUM CARBURIZING OF NiTi SHAPE 
und Adhasion MEMORY ALLOYS 
sse entstehen 
ler fehlenden 
eingebrachte 
ei M. Bruncko, P. Kirbis, R. Rudolf, M. Kos, I. Anzel 
und von der 
Harte seiner University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, SI-2000 Maribor, 
ihergehenden Slovenia, Europe 
Abspanen der 
1 der weichen 
leiRraten bei 
en. 
ABSTRACT 
t werden: 
d deren Harte This paper studies the usability of low-pressure vacuum carburizing process for improving 
en, Adhasion the wear resistance of NiTi shape memory alloys. It is well known that B2 austenitic parent 
lastisch indu- phase exhibits an excellent wear resistance. On the other hand, the wear resistance of the 
halten grober B19’ martensite phase is weak and must be improved for some applications. One of the 
suitable techniques for improving the surface properties in metallic materials is low-pressure 
ab. Durch die vacuum carburizing. The process is performed under oxygen free hydrocarbon gas 
ein adhasives atmosphere at partial pressure lower than 20 mbar. This is obligatory due to high affinity of 
können stark titanium to oxygen. The low-pressure vacuum carburizing consists of the cycles of active 
lern. (saturation) and passive (diffusion) stages. The desired depth of the carburized zone and 
s zeigen sich corresponding target concentration profile of carbon can be supervised by controlling the 
proder agiert, duration of these two stages. 
In this research work, the kinetics of the process and the microstructural changes during 
wesentlichen carburizing of NiTi shape memory alloy with an equiatomic composition in a low-pressure 
trachtung von acetylene atmosphere were monitored. 
mperatur und 
1. INTRODUCTION 
y of abrasive 
act ee or NiTi alloys are the most technological important shape memory alloys use for wide range of 
nd steel”, Mat. applications, which are based on shape memory effect and superelasticity [1]. 
ducing effects Characteristic for shape memory materials is an unconventional, unique correlation of strain, 
at”. Tribol. Int., stress and temperature, which is based on crystallographic reversible thermoelastic 
martensitic transformation. The low-temperature and the high-temperature phases are, 
of cast MMCs analogous to steel technology, named martensite and austenite (also parent phase). The 
5. transformation start and finish temperatures are As (austenite start) and Ar (austenite finish) 
and Ms (martensite start) and Mr (martensite finish) during heating and cooling, respectively.