Mechanical and tribological properties of cold sprayed Ni/CrC-NiCr metal matrix composites
Bibliographic record
Abstract
Cold spray (CS) is a solid-state deposition method involving severe plastic deformation of micron-sized powder particles accelerated to supersonic speeds. These particles are propelled through a compressed gas stream, such as air, nitrogen, or helium, using a de Laval nozzle. Since CS operates at low temperatures, no melting takes place during deposition. This offers a distinct advantage over other thermal spraying techniques, resulting in unique and significant advantages. Metal-matrix composites (MMC) combine the high hardness, wear resistance, and thermal stability of ceramics with the ductility, toughness, and thermal conductivity of metals.In the development of coatings through CS technology, the feedstock powder is crucial for achieving the desired engineering properties, and it becomes more significant when cermet MMC powders are used. This dissertation aims to experimentally investigate the mechanical and tribological properties of a cold-sprayed cermet based MMC. Chromium carbide-nickel chromium (CrC-NiCr) was used as the cermet particle, where CrC is a ceramic and NiCr is a ductile binder. This cermet particle was used in the MMC by using Ni as the overall binder. Therefore, the MMC is designated as (CrC-NiCr)/Ni. The first part of the study focuses on: (i) investigating the influence of increasing the metallic (NiCr) binder percentage in the cermet particle, and (ii) exploring the effects of varying the matrix-to-cermet ratio, i.e. Ni to (CrC-NiCr) ratio, in the feedstock blend on the microstructure and mechanical properties of the CS deposits. Results indicate that increasing the binder phase percentage in the cermet particles enhances deposition efficiency, cermet area fractions, and interparticle adhesion. This also results in coatings with porosity less than 1%, as well as improved ductility and shear strength. To address inter-splat defects and brittleness of the MMCs, the second part of this study examines the effects of post-spray annealing on the mechanical properties and microstructure. Scanning transmission electron microscopy (STEM) demonstrated improved interparticle bonding between matrix splats, with fractographic analyses indicating a shift from brittle to ductile fracture mechanisms. Mechanical tests reveal that post-process annealing significantly enhances the ultimate tensile strength (UTS), elongation, and adhesion shear strength of the coatings, however, it adversely affects coating hardness. The third part of this study investigates the effects of various post-spray heat treatments on the microstructure and tribological behavior of cold-sprayed Ni/CrC-NiCr metal matrix composite (MMC) coatings. Post spray (PS) laser heat treatment (LHT) and plasma arc heat treatments (PAHT), along with two furnace annealing temperatures were employed. Results show the wear rate of the MMCs is significantly influenced by the type of heat treatment. PS-LHT and PAHT facilitated the formation of thin oxide tribofilm (mainly Cr2O3) that acted as solid lubricants, reducing metal-to-metal contact and abrasive wear.--Author's abstract
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".