Cold Spraying as a Repair Method for Crankshaft Journals
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Applied mechanics (MPAME), MSc
Publicerad
2023
Författare
Blomgren , Matilda
Gunnarsson, Stefán
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
In this study, the feasibility of repairing crankshaft journals with cold spraying was
investigated. It was researched through a systematic literature study, and contact
with cold spraying companies, with the main focus on the parameters affecting the
coating properties; surface hardness and adhesive strength, machinability of the cold
sprayed coating, and limitations to the shape and size of repair. The most critical
factor affecting the deposit hardness and adhesive strength is the impact velocity.
The size and shape of the repair are limited by both the cold spraying process capacity
and the crankshaft design. The design elements limiting shape and size are the
critical zones; radiuses, oil holes, and the lower part of the pin journals. Machining
the cold sprayed coating is possible, however, it can be problematic due to the critical
zones and simultaneous machining of two materials. The cold spraying companies,
which differ by the pressure system they specialize in, have recommended materials
for the repair, only the recommendation from the high pressure cold spraying company
can fully meet the design requirements. For low-pressure cold spraying, three
feedstock materials have been recommended, Ni/Zn, Al/Zn, and Cu/Zn composites.
For high-pressure cold spraying, two feedstock materials have been recommended,
a tungsten carbide with nickel and cobalt, and a tungsten carbide with stainless
steel. The latter can be further developed to meet the crankshaft requirements.
The recommended materials must comply with Volvo’s list of substances. The recommended
feedstock materials include substances on the lists. The materials shall
therefore be assessed if allowed to be used, if not it must be considered if other
feedstock materials are available, or if the material open for development can be optimized
with the lists in mind. A detailed recommended plan of testing is presented
with the purpose of defining the unknown parameters of the coatings; compatibility
and strength, and to verify that the coating meets all journal requirements.
Beskrivning
Ämne/nyckelord
Cold spray , Crankshaft , Journal , Low-pressure cold spray , High-pressure cold spray