55
Contemporary Machining Processes
thick layers exhibiting hardness above 800 HV are generated. Similarly, (α+β)-Ti
alloys like Ti-4, 5Al–3V–2Mo–2Fe (SP700), and β-Ti alloys like Ti–10V–2Fe–3Al
can be enhanced by laser nitriding (Höche et al., 2015).
Laser carburizing was initially performed using graphite coatings in laser surface
hardening of steels. At present, laser carburizing is applied to commercially pure
iron, plain carbon, and low-alloy steels. It can be achieved by two different mechanisms: (a) laser surface alloying, which involves melting of a surface layer while carbon enters the liquid phase; and (b) solid-state diffusion of carbon, activated by laser
heating (Katsamas and Haidemenopoulos, 2001). Laser carburization also proves
successful for austenitic stainless steel and non-ferrous materials such as aluminum
and silicon in methane atmospheres (Höche et al., 2015).
Laser surface treatment also has an impact on technical grade ceramics, e.g.,
Si 3 N 4 or ZrO 2 , causing changes in their topographical, chemical, microstructural,
compositional, mechanical, and thermal properties. Changes in hardness and the
resulting crack length from diamond indentation demonstrate modification of the
fracture toughness K 1c after fiber laser engineering of surfaces of these two ceramics
(Shukla and Lawrence, 2015).
Laser is also used for supporting other surface engineering techniques, for example, enhanced electroplating. In this method, irradiation of a laser beam on a substrate
(cathode) during electrolysis promotes drastic modification of the electrodeposition
process in the irradiated region. Other applications of lasers to surface engineering
are laser cleaning, paint stripping or laser surface roughening. The latter, executed
with pulses from an excimer laser, improves adhesion of glue to a surface. Laser
shock hardening or “laser shot peening” has emerged as an industrial process able
to create a compressive stress in a surface and thus increase fatigue strength of a
component’s material (Steen, 2003).
1.10.4 remanufacTuring wiTh laser cladding Technology
Even though laser cladding remanufacturing (LCR) has been researched actively
for several decades and proved to be an effective repair technology, the quality and
repeatability of cladding layers are still the key issues in the LCR technology. There
are some unquestionable benefits of LCR, but also some important challenges which
can be found in the literature (Liu et al., 2017). Among the advantages, the following
should be mentioned:
• LCR is applied to both surface engineering and three-dimensional deposition forming.
• Inherent rapid heating and cooling during the LCR process improve the
microstructure and property of cladding layers.
• Sound metallurgical bonds between an added metal and a base material are
achieved.
• LCR produces very few microcracks and distortions.
• The LCR technique has the ability to manufacture multifunctional homogenous or heterogeneous structures.
Contemporary Machining Processes
thick layers exhibiting hardness above 800 HV are generated. Similarly, (α+β)-Ti
alloys like Ti-4, 5Al–3V–2Mo–2Fe (SP700), and β-Ti alloys like Ti–10V–2Fe–3Al
can be enhanced by laser nitriding (Höche et al., 2015).
Laser carburizing was initially performed using graphite coatings in laser surface
hardening of steels. At present, laser carburizing is applied to commercially pure
iron, plain carbon, and low-alloy steels. It can be achieved by two different mechanisms: (a) laser surface alloying, which involves melting of a surface layer while carbon enters the liquid phase; and (b) solid-state diffusion of carbon, activated by laser
heating (Katsamas and Haidemenopoulos, 2001). Laser carburization also proves
successful for austenitic stainless steel and non-ferrous materials such as aluminum
and silicon in methane atmospheres (Höche et al., 2015).
Laser surface treatment also has an impact on technical grade ceramics, e.g.,
Si 3 N 4 or ZrO 2 , causing changes in their topographical, chemical, microstructural,
compositional, mechanical, and thermal properties. Changes in hardness and the
resulting crack length from diamond indentation demonstrate modification of the
fracture toughness K 1c after fiber laser engineering of surfaces of these two ceramics
(Shukla and Lawrence, 2015).
Laser is also used for supporting other surface engineering techniques, for example, enhanced electroplating. In this method, irradiation of a laser beam on a substrate
(cathode) during electrolysis promotes drastic modification of the electrodeposition
process in the irradiated region. Other applications of lasers to surface engineering
are laser cleaning, paint stripping or laser surface roughening. The latter, executed
with pulses from an excimer laser, improves adhesion of glue to a surface. Laser
shock hardening or “laser shot peening” has emerged as an industrial process able
to create a compressive stress in a surface and thus increase fatigue strength of a
component’s material (Steen, 2003).
1.10.4 remanufacTuring wiTh laser cladding Technology
Even though laser cladding remanufacturing (LCR) has been researched actively
for several decades and proved to be an effective repair technology, the quality and
repeatability of cladding layers are still the key issues in the LCR technology. There
are some unquestionable benefits of LCR, but also some important challenges which
can be found in the literature (Liu et al., 2017). Among the advantages, the following
should be mentioned:
• LCR is applied to both surface engineering and three-dimensional deposition forming.
• Inherent rapid heating and cooling during the LCR process improve the
microstructure and property of cladding layers.
• Sound metallurgical bonds between an added metal and a base material are
achieved.
• LCR produces very few microcracks and distortions.
• The LCR technique has the ability to manufacture multifunctional homogenous or heterogeneous structures.