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Maintenance & Calibration

Thermal spraying has many benefits in equipment maintenance and calibration. In maintenance, it can repair mechanical parts, extend their lifespan and restore or improve performance. It also provides anti-corrosion protection for outdoor equipment. In calibration, it can improve the measurement accuracy of measuring tools and probes. It can also create calibration standards for surface roughness and hardness. It also lists application cases, cost-benefit analysis and other methods. Translation, writing assistance, image generation and more functions are provided.

How to Use Thermal Spray in Maintenance & Calibration?

1. In Maintenance

1.1 Surface Restoration of Machinery Parts

Worn Shafts and Rotating Components:
Assessment: 

When dealing with worn shafts in industrial machinery such as motors, turbines, or pumps, first, measure the extent of wear. This can be done using precision measuring tools like micrometers or profilometers. For example, if a shaft has a worn diameter, the worn area’s dimensions and the original specifications need to be precisely determined.

Preparation:

 Clean the worn surface thoroughly to remove any dirt, grease, or debris. Abrasive blasting, such as sandblasting, can be used to create a suitable surface profile for better coating adhesion. The blasting process roughens the surface, increasing the contact area for the thermal spray coating.

Spraying:

 Select a suitable thermal spray material. For shafts that require good wear resistance and corrosion protection, materials like tungsten carbide – cobalt (WC – Co) coatings applied via high – velocity oxygen – fuel (HVOF) spraying can be a good choice. The HVOF process propels the coating particles at high speeds, resulting in a dense and strongly – bonded coating. The sprayed coating fills in the worn areas and restores the shaft’s original dimensions, providing enhanced wear resistance.

Damaged Dies and Molds:
Identification: 

In the manufacturing industry, dies and molds often develop cracks, erosions, or surface imperfections after multiple uses. Visual inspection and non – destructive testing methods such as dye – penetrant testing or ultrasonic testing can be used to identify the damaged areas.

Surface Preparation: 

Similar to shaft restoration, the damaged areas need to be cleaned and pre – treated. Chemical cleaning may be necessary to remove any residual plastics or metals adhered to the mold surface. After cleaning, a grit – blasting process can be used to prepare the surface for thermal spraying.

Coating Application: 

For dies and molds, materials like nickel – based alloys or ceramic coatings can be applied. Plasma spraying is often used for these applications due to its ability to handle a wide range of materials and produce high – quality coatings. The sprayed coating can repair the damaged areas, improve the surface finish, and enhance the die or mold’s resistance to wear, corrosion, and thermal stress, thereby increasing its lifespan and maintaining the quality of the manufactured products.

1.2 Protection Against Corrosion

Outdoor Equipment and Structures:
Analysis:

 Outdoor equipment such as antennas, transmission towers, and storage tanks are constantly exposed to environmental factors like moisture, salt spray, and pollutants. A comprehensive inspection to assess the current condition of the equipment’s surface and identify areas prone to corrosion is the first step.

Surface Treatment: 

The surfaces need to be thoroughly cleaned to remove rust, scale, and other contaminants. This can involve mechanical cleaning methods like wire brushing or chemical cleaning using rust removers. Once clean, the surface can be prepared for thermal spraying.

Thermal Spray Coating: 

Zinc – based coatings are commonly used for corrosion protection. Flame spraying is a relatively simple and cost – effective method for applying zinc coatings. The zinc coating acts as a sacrificial anode, corroding preferentially and protecting the underlying substrate from rust and other forms of corrosion. The coating thickness can be adjusted according to the expected environmental exposure and the required protection period.

2. In Calibration

2.1 Calibration of Measuring Instruments

Surface Preparation for Gauges and Probes:
Inspection: 

Measuring gauges and probes used in precision manufacturing or metrology need to have accurate and consistent contact surfaces. Inspect the surfaces for any irregularities, wear, or contamination that could affect the measurement accuracy.

Surface Conditioning: 

Clean the surfaces using solvents and mild abrasives to ensure a smooth and clean base for the thermal spray coating. The goal is to achieve a surface roughness that promotes good adhesion without sacrificing the precision of the instrument’s contact surface.

Coating Application: 

For electrical conductivity – based measurement probes, a thin layer of gold or a gold – alloy coating can be applied using thermal evaporation or a low – energy plasma – assisted thermal spray process. The coating thickness needs to be carefully controlled to achieve the desired electrical properties. This calibrated coating ensures accurate and reproducible electrical measurements, for example, in conductivity or resistivity measurements.

Calibration of Wear – Sensitive Instruments:
Assessment:

 Instruments like tribometers, which measure friction and wear, rely on accurate and consistent surface characteristics. The wear surfaces of these instruments need to be calibrated regularly to ensure reliable results.

Surface Preparation: 

The wear – testing surfaces are prepared by polishing to a specific roughness and then cleaning to remove any polishing residues.

Coating Deposition:

 A precisely calibrated ceramic coating with a known hardness and friction coefficient can be applied using thermal spray. This coating provides a standard reference surface for wear testing, allowing for accurate calibration of the instrument and reliable comparison of different material – on – material wear tests.

2.2 Creation of Calibration Standards

Surface Roughness Standards:
Design and Preparation: 

To create calibration standards for surface roughness measurement, a substrate with a known flatness and material properties is selected. The surface is then prepared through grinding and polishing to a near – perfect finish as a starting point.

Thermal Spray Coating: 

Controlled – porosity ceramic coatings can be applied using plasma spraying. By adjusting the spraying parameters such as powder feed rate, plasma power, and stand – off distance, coatings with different roughness levels can be created. These calibrated surfaces with precisely defined roughness values can be used to calibrate surface – profiling instruments like profilometers, ensuring accurate and traceable roughness measurements.

Hardness Standards:

Base Material Selection: 

For hardness calibration standards, a material with a well – characterized and homogeneous hardness, such as a hardened steel alloy, is chosen as the substrate.

Coating and Calibration:

A series of coatings with different hardness values can be deposited on the substrate using thermal spray. For example, different ceramic – metal composite coatings can be prepared with varying compositions and microstructures. The hardness of these coatings can be measured and calibrated using standard hardness – testing methods such as Rockwell or Vickers hardness testing. These calibrated hardness standards can then be used to verify the accuracy of hardness – testing equipment in industrial and research settings.

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