thermal spray powder: 五月 2015

2015年5月28日星期四

Principle and application of plasma spraying

In the high temperature surface process technology, when some gas (such as Nitrogen, argon, hydrogen, helium and so on) produces plasma thought compressive arc, The energy of the plasma arc concentrated temperature is very high, its flame flow temperature above ten thousand degrees Celsius, it can melt all solid engineering material. This is plasma spraying.

In plasma spraying process, the material to be deposited— typically as a powder, sometimes as a liquid, suspension or wire — is introduced into the plasma jet, emanating from a plasma torch. In the jet, where the temperature is on the order of 10,000 K, the material is melted and propelled towards a substrate.

Applications:

Surface of Traction equipment

The roll surface

Most classical thermal spraying

This technique is mostly used to produce coatings on structural materials. Such coatings provide protection against high temperatures (for example thermal barrier coatings for exhaust heat management), corrosion, erosion, wear; they can also change the appearance, electrical or tribological properties of the surface, replace worn material, etc.

It can also be used for spray powder processing (spheroidization, homogenization, modification of chemistry, etc.).This technique with variation may also be used to create porous structures, suitable for bone ingrowth, as a coating for medical implants.

The initial parameters of plasma system should be carefully set, then the spraying gun can run continuously for several hours under standard condition. Plasma spraying is better than arc or oxygen flame spraying with lower oxygen content and porosity.

What is self-molten alloy?

Self-molten alloy is one kind of alloy which has a lower melting point, deoxidizing and slagging on its own in melting process and can “wetting” base material surface then metallurgical bonding. It can form high hardness of the dispersion strengthening phase in solid solution after the alloy solidification, increasing the strength and hardness of alloy.

Nowadays, most self-molten alloys are made from Fe, Ni, cobalt-based alloys, and add appropriate amount of B and Si elements. After the adding of B and Si, the coating can be Heated to above 1000 ℃, reaching the molten state, combining with matrix , eliminating porosity of the coating, fully embodying the superior performance of coating material.

The remelting of (Wc Co thermal spray powder or others) coating can be heated by flame, high frequency induction and vacuum oven, what we should pay attention to is that deformation and the changing of matrix organization is inevitably because the heating temperature above 1000 ℃.

2015年5月19日星期二

Excellent-performance tungsten powder for tungsten carbide manufacturing

Tungsten carbide power is an excellent- performance materials which made from tungsten and carbon, it is prominently featured with the same hardness with diamond and high toughness when mixed with appropriate metal blinder. So, tungsten carbide powder is mainly cemented carbide powder for tungsten carbide manufacturing, applied to many industrial tools and wear-resistant parts making, meeting various performance requirements needs of the end users.

There are two reasons why mining conditions become more and more difficult, one is the growth of global demands for raw materials with each passing day, and the other one is the available mineral resources decreasing at the same speed. Excellent-performance tungsten carbide powder can be used for many technological processes, for example, drilling and milling for modern construction with metal materials efficiently and reliably.

Diamond bit for development and drilling of oil gas is also made from tungsten carbide powder, doing highly impactive and abrasive working under the condition of high temperature corrosion, theses drills must keep excellent reliability. The tungsten carbide tools are more popular than others because of its low costs and high benefits. Tungsten carbide power can longer the productions’ service life significantly, reducing the cost of equipment machine halt and replacement efficiently, then creating an operation environment which with low consumption cycle and low parts replacing frequency.

2015年5月17日星期日

Production methods of thermal spraying ceramic coating materials

Ceramic materials are brittle, basically preparation of coating with thermal spraying technique in powder form, mechanical process and physical-chemical process are the two main ways to preparation of thermal spraying ceramic coating powder materials. Mechanical process includes crushing method，atomization method, mixing method, mechanical Alloying and so on, and physical-chemical process contains bonding process, chemical reduction method, pyrolysis method, quench method, combustion method etc. . liquidity and shape pf powder, apparent density, sedimentation efficiency and other wholesomeness are affected by the preparation way of ceramic powder, so it’s have great influence on thermal spraying process performance.

Except powder form of thermal spraying powder ceramic coating materials, the other form is composite wire which contains ceramic particles, it mainly includes filling composite wires and flexible composite wires. The former is made of mixing, heating, squeezing of ceramic powder and seldom adhesives. Common coating metal materials of Metal filling materials composite wire are Ni, Cu, Al, steel, stainless steel and so on, common ceramic particles are WC, Al2O3, TiO2, Cr2O3 etc.

Related articles
Our advanced surfacing technology
Performances and classifications of spraying coating
Classifications of thermal spraying technology (part one)
Classifications of thermal spraying technology (part two)
Cemented carbide coating

2015年5月12日星期二

Applications of thermal technique in energy industry

In china, coal are the main fuel of power plant boiler and industrial boiler. “four tubes” of boiler work under bad environment of high temperature, high pressure, gas corrosion and grains ablation, high temperature corrosion and abrasion generate easily, then thinning the wall tubes, leading to damage of equipment even accidents. The surface of Induced draft fan, air cylinder and some other equipment which high-speed gas flows through, abrasion, cavitation and other reasons may lead to efficacy loses, causing heavy losses. Many moving parts (for example, axle), scraped because of mechanical abrasion. In addition, electric power transmission & transformation equipment and all kinds of steel structures of power plant suffer serious industrial atmospheric corrosion because of they are always in the outdoor environment. All the solutions can be solved by thermal spray techniques, strengthening and improve its service life greatly, or restoring its workability by repairing, then increasing production safety and economic benefit of powder plant.

High-temperature corrosion and abrasion not only have great effects on safe operation of boiler, but also cause huge economic loss, it’s urgent to be solved in safety problem of boiler. It has been proved that spraying high chromium NiCr wire coating with arc spraying is an ideal method, which has been widely used in many countries. And except wire, powder is common used in thermal spray technique, especially WC spray powder, there are more and more china spray powder suppliers and manufacturers, accelerating the development of thermal spraying technique.