Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Plasma-assisted nitriding of M2 tool steel: An experimental and
  theoretical approach   Present work was aimed to investigate the effect of nitriding time; 1, 1.5,
2.5 & 3.5 h, on surface characteristics & mechanical properties (surface
nano-hardness, hardness Vickers, and adhesion) of AISI M2 tool steel.
Mechanically effective compound (4 to 17.6 um) and diffusion layers (50.8 to
82.4 um) were obtained. Plasma nitriding considerably improved Surface
engineering has been recognized as a family of technologies used to modify or
improve the surface properties of a substrate. Nano-hardness, E-moduli and
resistance to scratch of AISI M2 steel. Surface properties enhancement was
associated to two harmonious effects at the nano-scale resulted by (a) stable
nitride phases formation such as: gamma-Fe4N, epsilon-Fe2,3N, and (b) no
brittle nitride networks and no critical decarburization of the steel upon
nitriding. Thermodynamic calculations are in agreement with the experimental
findings.

12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg