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Remanufacturing and Advanced Machining
Pathak and Saha (2017) indicate that restoration of dimensionally inaccurate
components or especially damaged parts through cold spray has become a great
achievement, especially in reparation of surface damage to intricate shapes. In the
process of restoration, a metallic powder is deposited in distorted sections. The host
and powder materials may be dissimilar, which is very useful to improve the various
mechanical properties of a part, depending on requirements. Unlike other repairing
processes, cold spray does not generate undesirable thermal stresses that can result in
premature failure of a component. The authors emphasize that this process is being
widely used in the automotive and industrial marketplaces and is ideally suitable for
aerospace materials like magnesium and titanium. They list benefits and examples
of repair and remanufacturing by cold spray:
• Significant total cost savings.
• Repair time reduction. Cold spray can be used to repair a part in-situ and
eliminate assembly and testing costs.
• Improved production yield. Cold spray can be applied to used-up parts
returned from the field, but it can also be used to salvage parts with manufacturing defects, making them useful.
Fauchais et al. (2014) describe many areas where thermal spray coatings may be used
as a repairing technique. In the case of aluminum components that are difficult to
repair by welding due to its high-specific thermal conductivity and high coefficient
of thermal expansion, they highlight the ability of the low-pressure cold spray technique to replace welding in repairing cracks.
2.5 VACUUM PLASMA SPRAYING
Vacuum plasma spraying refers to transport of particles from a gaseous source to a
substrate surface along a linear motion trajectory (Gushcha, 2009). When vacuum
is around 10 –2 Pa and less, the process is classified as a vacuum evaporation, pressure 1 Pa constitutes the so-called cathodic spraying, while 10 –2 –10 –1 Pa is typical for magnetron sputtering and ion–plasma beam sputtering. Vacuum spraying is
used for sputtering of metals such as Al, Аu, Сu, Cr, Ni, V, Ti, alloys, e.g., NiCr or
CrNiSi, chemical compounds like silicides, oxidizes, borides, carbides, etc., complex
glasses, and cermets (Gushcha, 2009). Vaßen et al. (2018) state that VPS is the most
often used thermal spray process for deposition of dense, high-quality 3-mm thick
tungsten coatings. Kim et al. (2020) report deposition of hafnium carbide (HfC) and
titanium carbide (TiC) with the VPS method to form ultra-high-temperature ceramic
(UHTC) coatings in the form of both single-layer HfC and TiC and multilayer HfC/
TiC coatings. Thicknesses of the HfC and TiC single-layer coatings were 165 and
140 µm, respectively, while the thicknesses of the HfC and TiC layers in the HfC/
TiC multilayer coating were 40 and 50 µm, respectively. No oxides were observed
in any of the coating layers and average porosity was approximately 16.8% for the
HfC coating and 22.5% for the TiC coating. The hardness values of the HfC and TiC
layers in the multilayer sample were 1563.5 and 1059.2 HV, respectively. Kim et al.
Remanufacturing and Advanced Machining
Pathak and Saha (2017) indicate that restoration of dimensionally inaccurate
components or especially damaged parts through cold spray has become a great
achievement, especially in reparation of surface damage to intricate shapes. In the
process of restoration, a metallic powder is deposited in distorted sections. The host
and powder materials may be dissimilar, which is very useful to improve the various
mechanical properties of a part, depending on requirements. Unlike other repairing
processes, cold spray does not generate undesirable thermal stresses that can result in
premature failure of a component. The authors emphasize that this process is being
widely used in the automotive and industrial marketplaces and is ideally suitable for
aerospace materials like magnesium and titanium. They list benefits and examples
of repair and remanufacturing by cold spray:
• Significant total cost savings.
• Repair time reduction. Cold spray can be used to repair a part in-situ and
eliminate assembly and testing costs.
• Improved production yield. Cold spray can be applied to used-up parts
returned from the field, but it can also be used to salvage parts with manufacturing defects, making them useful.
Fauchais et al. (2014) describe many areas where thermal spray coatings may be used
as a repairing technique. In the case of aluminum components that are difficult to
repair by welding due to its high-specific thermal conductivity and high coefficient
of thermal expansion, they highlight the ability of the low-pressure cold spray technique to replace welding in repairing cracks.
2.5 VACUUM PLASMA SPRAYING
Vacuum plasma spraying refers to transport of particles from a gaseous source to a
substrate surface along a linear motion trajectory (Gushcha, 2009). When vacuum
is around 10 –2 Pa and less, the process is classified as a vacuum evaporation, pressure 1 Pa constitutes the so-called cathodic spraying, while 10 –2 –10 –1 Pa is typical for magnetron sputtering and ion–plasma beam sputtering. Vacuum spraying is
used for sputtering of metals such as Al, Аu, Сu, Cr, Ni, V, Ti, alloys, e.g., NiCr or
CrNiSi, chemical compounds like silicides, oxidizes, borides, carbides, etc., complex
glasses, and cermets (Gushcha, 2009). Vaßen et al. (2018) state that VPS is the most
often used thermal spray process for deposition of dense, high-quality 3-mm thick
tungsten coatings. Kim et al. (2020) report deposition of hafnium carbide (HfC) and
titanium carbide (TiC) with the VPS method to form ultra-high-temperature ceramic
(UHTC) coatings in the form of both single-layer HfC and TiC and multilayer HfC/
TiC coatings. Thicknesses of the HfC and TiC single-layer coatings were 165 and
140 µm, respectively, while the thicknesses of the HfC and TiC layers in the HfC/
TiC multilayer coating were 40 and 50 µm, respectively. No oxides were observed
in any of the coating layers and average porosity was approximately 16.8% for the
HfC coating and 22.5% for the TiC coating. The hardness values of the HfC and TiC
layers in the multilayer sample were 1563.5 and 1059.2 HV, respectively. Kim et al.