Diffusion thermodynamic behavior of milling Ti-6A1-4V alloy in liquid
nitrogen cryogenic cooling
Received: 20 July 2017 /Accepted: 17 November 2017 /Published online: 29 November 2017
Springer-Verlag London Ltd., part of Springer Nature 2017
This paper presents the first comprehensive investigation on milling Ti–6Al–4Valloy in cryogenic cooling, and it mainly focuses
on the effect of diffusion wear behavior of WC-Co tool in operations. Diffusion coefficient calculation model of elements is
established considering cutting temperature. A series of conventional and cryogenic cooling experiments are conducted, as well
as element diffusion behaviors are observed and analyzed by SEM and EDS, and the diffusion coefficient of model is verified.
Similarly, the influence of cutting temperature on diffusion wear on contact surface of tool/workpiece is studied. Through the
phase diagram analysis of elements, the affinity behaviors between them are researched, and then the mechanism of diffusion
wear is deduced. The results showed that the calculation results of diffusion coefficient are similar with the measurement ones
under two kinds of cooling model at 150 m/min speed, and they are close to diffusion effect of 1200 and 800 K, respectively.
Moreover, Co element has the most difficult diffusion ability, but C and Ti are easiest. At cryogenic conditions, their diffusion
degrees are all apparent decline compared with conventional one, and the cutting temperature rise is slow with the increase of
cutting speed. Although the former cutting force increases, the workpiece rebound is well suppressed. Furthermore, the friction
degree of tool/workpiece is decreased on contact surface, and the elements diffusion behavior of carbide tools is improved. In
cryogenic cooling condition, decreased friction degree of tool/workpiece and the weakening of solid solution degree between Ti,
W, and Co elements are the main reasons for effectively inhibit of the diffusion wear.
Because titanium alloy had poor thermal conductivity coeffi-
cient, high specific heat and short contact length between the
chip and tool rake face. The generated heat cannot be dissi-
pated effectively, which was mainly concentrated in a smaller
range of the cutting zone and near the tool cutting edge. The
heat made cutting temperature very high [1–3]. In addition,
the kind alloy material had bigger activity and strong affinity
with tool material. So in machining process, workpiece mate-
rial was easily cohered in tool surface. Under the effect of
cutting high temperature, the elements diffusion behavior be-
tween tool and workpiece material would be inevitable oc-
curred. Especially in high machining speed, the phenomenon
was more intense [4, 5].
It is necessary to carry out in-depth study on the principle
and mechanism of diffusion between tool and workpiece and
to improve tool cutting performance and service life . Li
et al. found that in above the temperature of 900 K, element
diffusion of W and Co firstly began, and it resulted in the
decrease of tool hardness near the diffusion interface [7, 8].
Liang and others [9, 10] adopted a carbide tools using WC as
matrix with Ni
Al adhesive to cut titanium alloy, while the
influence law of adhesive Ni
Al on tool was investigated.
The experimental results showed that the processing perfor-
mance of WC-10 Ni
Al tool was better than that of WC-8Co
carbide one, which was due to high hardness of high temper-
ature chemical inertia caused by Ni
Al adhesive at high speed.
Loladze  reported that the adhesive wear was the main
* Fengbiao Wang
School of mechanical Engineering, Shenyang Ligong University,
Shenyang 110159, China
Aerospace Research Institute of Materials and Processing
Technology, Beijing 100076, China
School of mechanical Engineering, Dalian University of Technology,
Dalian 116024, China
The International Journal of Advanced Manufacturing Technology (2018) 95:2783–2793