Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Effect of laser surface hardening on a low carbon steel substrate wear
  and hardness   Laser surface hardening (LSH) is an effective process to produce hard and
wear resistant steel surfaces. This work produced hardened surfaces using a
fiber laser in a bare (B. uncoated) and carbon-coated (C) conditions. The
obtained hardness and microstructure were compatible to martensite (B) and
cementite (C) major constituents. A low coefficient of friction was obtained
using C-condition. The treated surface also presented little damage during a
reciprocating wear against a hard metal sphere.

8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci