ball mill repair

 

repair mandrel

Repair Spline Mandrel; compare method Arc welding with Arc spray coating.

As you know that repair or overlaying using arc welding will generate high heat input to the base metal due tot melting the electrode to the base metal. While your Spline Mandrel material is high tensile steel material high heat during welding will form an area known as HAZ (Heat Affected Zone) and this zone will reduce the tensile strength of the spline mandrel.

High heat will also effect on the base material composition will change, the unit will easily deform because of difficult to control the heat during welding.

While using arc spray the method of applying as follows:

Preparation
- Undercut to remove the worn area (the fatigue area) clean and uniform.
- Blasting to make the space rough and clean using aluminum oxide size G. 25
- Place the mandrel to the late machine and turning speed at 50 RPM to 125 RPM depend on the diameter
- Spray with bond coating +/- 200 microns using bond arc 75B (nickel base) bond strength 10.000 psi
- Spray with chrome steel material (60 T = 13% chrome) combine with high abrasion material ( 95 MXC)
The result chrome steel with high abrasion resistance
Hardness (micro hardness) 50 – 55 Rc

Finishing by grinding on lathe machine to final size.

For your information AISI 4420 SS is a high chrome SS material, our product for this material TAFA 60 T (Enclose the technical data).

Ceramic Coating

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No question our coating lasts longer. What’s surprising is how cost-competitive we are. Our website will acquaint you with what makes our rod-form ceramic unique from other coatings and our long history of saving money for major companies.

Performance, longevity & value is your answer for all types of wear challenges You can get the best without paying more. We are very competitively priced and over time provide an outstanding cost savings. Current customers are well aware of the benefits & value of the Saturn process and have become our strong advocates. We guarantee our rod-form ceramic coating will outperform any other coating you are currently using. A Guaranteed Satisfaction Policy can be designed to ensure positive return on investment

"This coating helps us control our maintenance costs and reduce the amount of time our pumps are down for inspection and repair."

Spray-On horsepowerCeramic Coatings
By Bob Ryder

Who would have thought that horsepower could be gained from coating internal engine components? Internal engine components are made from dissimilar metals. Due to the lack of metallurgical similarities of these components, they absorb and dissipate heat at different cycling periods. The ability to protect and cool engine internal and external components actually contributes to noticeable horsepower and performance gains. The three major contributors to horsepower gain are heat resistance, friction reduction, and wear protection. Over the years, performance engine builders have been refining the leading edge of horsepower gains while experimenting with ceramic coatings. Ceramic coatings are used as a barrier between dissimilar metals to reduce friction, which cause heat, creating unwanted wear of internal engine components. By applying ceramic coatings to these dissimilar metal components, it will allow them to interface with one another more uniformly and compatibly. Prior to applying ceramic coatings to components, its surfaces must be prepped by media- or sandblasting. This will remove the component's outer crust surface and any contaminants, exposing the virgin metal underneath. Some feel that it is important to heat the component in an oven after it has been media- or sandblasted, to sweat out any additional contaminants or porosity from within its metallurgical molecular structure. If not, during the initial time the component is exposed to a heat cycle, some porosity may sweat to the surface and become trapped underneath the coated surface, causing the coated surface to de-laminate. It is very important for the component to be pure and clean before applying ceramic coatings. Ceramic coatings are available in a variety of coatings, including tungsten and titanium. The ceramic coatings are applied with an automotive detail touch-up gravity-fed spray gun with a nozzle size of about 0.8 inch, because its smaller size allows for better control. Most ceramic coatings are applied at 35 to 40 psi for solvent coatings and 50 to 60 psi for water-based coatings. It is best to apply ceramic coatings inside a spray paint booth using a respirator when using solvent- or water-based coatings. The ceramic viscosity, or thickness, is very thin and must be applied carefully, so it will not run. Most ceramic film application buildup is approximately 0.0003 to 0.001 inch. After the component is coated, it is inspected for uniform coverage, then allowed to air dry at room temperature to slowly begin the solvent- or water-based evaporation process, before placement in an oven to cure. It is best that the components are dried in an upright air-circulating oven to allow even heating for uniform curing of the component. The first increment of heat is 175 degrees Fahrenheit during ambient versus curing temperature transition for about 10 minutes, then cranked up to a cure temp of 600 degrees Fahrenheit for one hour. When building up a film barrier to 0.001 inch, this would affect clearances. After applying the ceramic film, the thickness is checked, then burnished with a ScotchBrite pad or similar material until the film thickness is no less than 0.0003 inch. This will allow the bearings to be run with its normal installed clearance. To polish Cermakrome coatings of exhaust manifolds and headers, it is best to use a vibrator type of polisher using Microbright ceramic balls and the appropriate polishing compound. The most common applications for ceramic coatings are on the exhaust system, manifolds, and headers. When ceramic thermal barrier coatings are applied to exhaust manifolds or headers, they provide two advantages. They protect the headers from rust and corrosion and also reduce heat loss, which translates into high power output. If the headers are internally coated, they will create a higher velocity of the hot exhaust gases and less turbulence due to a smoother surface. Pistons can also increase their performance characteristics with ceramic coatings. Coating the piston's crown and top will cause heat reflectivity, driving a percentage of any detonation energy back into the fuel burn zone, to increase fuel burn efficiency. It will also lower carbon buildup, which reduces detonation quality, as it builds up on the piston's crown and increases the risk of detonation damage to the piston crown surface. By protecting the crown and land diameter surfaces, it will allow for a leaner fuel mixture. Piston skirts can be coated to create an excellent dry sliding surface during engine start-up and will help eliminate skirt slap during initial engine run-in. Using a dry coating will fight against scuffing and abrasion of the piston skirt during its stroke travel inside the engine block cylinder. The inside of the piston can also be coated with an oil-shedding coating to cut parasitic drag and return oil to the sump faster. Ceramic coatings can also be applied over the piston ring contact face of OEM hard chromium, which provides lowering friction between the ring face and cylinder inner bore surface scuffing, and also improves wear resistance. Ceramic-coating the cylinder head's combustion chamber and exhaust ports will create a faster, hotter burn and help scavenge gases at a faster rate. The coating of these passages also creates thermal transfer from hot gases to the heads themselves. The cylinder head valley can be covered with an oil-shedding coating to speed the return to the sump. Some will coat the cylinder head's external surface with a thermal dispersant to aid in cooling the head. The valve-springs are coated with an oil-shedding ceramic to aid in the oil return to the sump. Camshaft bearing surfaces are not treated, but the rest of the camshaft is coated with a dry film lubricant. The crankshaft and connecting rods are sprayed with the oil-shedding coating to cut parasitic drag.An intake manifold is coated on the bottom with an oil-shedding coating to cut thermal heat transfer from the oil to the intake charge. It also helps eliminate fuel puddling on the intake manifold's internal floor surface. If the intake manifold floor is made too slick, it can hinder fuel and air atomization, not allowing the fuel and air mixture from tumbling, keeping the two suspended. The intake manifold's exterior can be ceramic-coated to reduce heat penetration, maintaining a cooler air/fuel mixture. Ceramic coatings have proven themselves in engine horsepower gain by reducing friction, heat, and wear.

Plasma Spray Coating Microstructure - Ceramic Coatings

Plasma sprayed Zirconia Titania Yttria Ceramic Composite Coating

over a Nickel Aluminium Bond Coat

Coating sectioned from a piston ring

Plasma sprayed 60/40 Alumina / Titania Ceramic Coating

Source : http://www.gordonengland.co.uk/pmg16.htm

New Life for Old Turbines -Sprayed Surface Lasts Five Times Longer

Reprinted from
Praxair News, July/August 2004
New Life for Old Turbines

TAFA-Sprayed Surface Lasts Five Times Longer Praxair Surface Technologies’ TAFA subsidiary in Concord, New Hampshire, has a uniqueapplication for hydroelectric companies that operatein areas where the water contains high particulateconcentrations and is very abrasive. Insteadof repairing the worn-out turbine wheelsevery three or four weeks, why not spray them with a coating that allows them to operate for more than six months without a repair? The process not only extends the operating life, butsaves thousands of dollars in weld-repair and labor costs for each water wheel. TAFA’s Equipment & Services Business Unit Manager Richard Thorpe developed the solution for coating the pelton wheel, a water turbine used by many hydroelectric companies, in 1996. Each pelton wheel has 21 arms, with a “bucket” at the end of each arm. Water is channeled into the turbine, hitting the wheel at high pressure and causing it to spin and generate electricity. In contrast to the United States or Europe, in some regions, such as Peru, Chile, China, India and Nepal, the water has extremely high levels of quartz and silica, which quickly erode the wheel’s surface and decrease its generating efficiency.

“Power companies try to keep the turbines’ generating efficiency high by constantly rotating and servicing the wheels,” Thorpe explained. “When the wheels are sprayed with a tungsten-carbide- type material, they last five times longer.”

TAFA’s first customer was Chilgener, an electric company in Chile, located in Santiago. “The coating extended the life of our turbine from 40 to over 200 days,” said Chilgener Production Manager Juan Moggia, “and we needed only 660 pounds of stainless steel for weld repair instead of 2,200 pounds.”

Thorpe explains how the process works. “We take a powder made of 86 percent tungsten carbide, 10 percent cobalt and four percent chromium, which is manufactured at our Indianapolis, Indiana, powder facility,” he said. “We run it through our high-velocity, oxy-fuel spray gun, Richard Thorpe says he’s trying to expand the coating’s use to India and other developing countries that need more power. where it’s semi-melted, accelerated to 500 to 700 meters per second velocity and then applied to the wheel’s surface.

The coating formed is extremely dense and hard, so it protects the wheel from damage for much longer period of time.” The initial success at Chilgener led to sales of the spray systems and coating solution to customers in Peru, India and Nepal. “Hydroelectric power is less expensive than oil and nuclear power,” Thorpe said. “We’re trying to expand the coating’s use throughour distributors to India and other developing countries thatneed more power.”

Praxair and the Flowing Airstream design are trademarks or registered trademarks of Praxair Technology, Inc. in the United States and/or other countries. Other trademarks used herein are trademarks or registered trademarks of their respective owners. The information contained herein is offered for use by technically qualified personnel at their discretion and risk without warranty of any kind.

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