Valve industry

Context: 

Pressure levels of over 600 bar 

Challenges: 

• Ball deformed by high pressure 
• Previous coating regularly flaked off due to aggressive media and hard sediments 
• Not possible to influence the structure of the base material 
• High differential pressure 

Industry: 

Gas production 

KVT solution: 

Coating method: Laser 

Coating material: 

KVT 433® 

Base material: 

Chrome-nickel steel 

Benefits to the customer: 

Laser welding combines powerful adhesive strength with the ability to finely dose thermal stress to the base material, thereby keeping it both minimal and superficial. All the mechanical properties of the substrate are thus preserved, with any superficial influence restricted solely to the welding zone. 

We use KVT 433, a particle-reinforced nickel brazing alloy, as the coating material. Based on stainless steel, this coating provides sufficient protection against abrasion and corrosion. It is made of 60 percent fine-grained tungsten carbides in a softer nickel matrix. Extreme pressure deforms the ball but does not cause the coating to flake off – thanks to the elasticity of the coating itself and the outstanding adhesion realized by laser welding. 

High-strength chrome-nickel steel serves as the base material. Though difficult to weld, it is perfectly suited to the given conditions. 

The surface of the ball is precisely defined and aligned with the requirement for impermeability. A surface that was too thin would increase the torque. 

The sealing system comprises a ball and rings that are ground onto each other and is also covered with a diamond-like carbon (DLC) coating to reduce friction. 

Context: 

Heat levels of up to 400 °C 

Pressure levels of up to 420 bar 

Industry:

Petrochemical industry 

Challenges: 

• Ball deformed by high pressure 
• Previous coating regularly flaked off due to aggressive media and hard sediments 
• Not possible to influence the structure of the base material 
• High differential pressure 

KVT solution: 

Coating method: Laser 

Coating material : KVT 433® 

Base material: Chrome-nickel steel 

Benefits to the customer: 

Laser welding combines powerful adhesive strength with the ability to finely dose thermal stress to the base material, thereby keeping it both minimal and superficial. All the mechanical properties of the substrate are thus preserved, with any superficial influence restricted solely to the welding zone. 

We use KVT 433, a particle-reinforced nickel brazing alloy, as the coating material. Based on stainless steel, this coating provides sufficient protection against abrasion and corrosion. It is made of 60 percent fine-grained tungsten carbides in a softer nickel matrix. Extreme pressure deforms the ball but does not cause the coating to flake off – thanks to the elasticity of the coating itself and the outstanding adhesion realized by laser welding. 

High-strength chrome-nickel steel serves as the base material. Though difficult to weld, it is perfectly suited to the given conditions. 

The surface of the ball is precisely defined and aligned with the requirement for impermeability. A surface that was too thin would increase the torque. 

The sealing system comprises a ball and rings that are ground onto each other and is also covered with a diamond-like carbon (DLC) coating to reduce friction. 

Context: 

Change of temperature from 150 to 400 °C 

Operational pressure of up to 300 bar 

Medium: Ethylene oxide 

Valves' service life was too short 

Industry: 

Chemical manufacturing 

KVT solution:

Coating method: Spray-and-fuse process 

Coating material: KVT 462® 

Base material: 1.4980 

Benefits to the customer: 

Since high pressure leads to extreme levels of torque when switching between systems, the operating shaft is designed and manufactured from a single piece. 

Particular attention is paid to the choice of material.  Heat-resistant materials created for the turbine and power plant construction industry are used for the balls. 

The choice of coating is determined in this case by technical feasibility, as the projected changes of temperature make it impossible to use the ceramic layers that would actually be resistant to the relevant chemicals. Since the base material expands under the influence of temperature, ceramic layers would crack open. 

KVT 462 is therefore used as a metallic coating. These Stellite-based fused coatings consist largely of cobalt. 

Context: 

Temperature: 200 °C 

Pressure levels: 10–80 bar 

Medium: Solvents 

Absolute gas impermeability despite more than 80,000 switching actions 

Industry: 

Chemical industry 

KVT solution: 

Coating method: Spray-and-fuse process 

Coating material: Combination of KVT 404® and KVT 405® coatings 

Base material: Duplex stainless steel 

Benefits to the customer: 

Solid, trunnion-mounted balls are used to absorb the tremendous forces involved. 

A sufficiently strong duplex stainless steel is selected as the base material. 

To guarantee an extremely long service life, a combination of KVT 404 and KVT 405 coatings is chosen. Both weld-on/fused nickel brazing alloys are harmonized as mating components. Their metallurgical bond protects them from sub-surface migration, while a high nickel content guards against corrosion. 

Context: 

Medium is highly abrasive due to the high flow velocity. 

Ball valve often jams because of the composition of the medium. 

Service life needs to be extended significantly. 

KVT solution: 

Coating method: HVOF 

Coating materials: KVT 231® and KVT 433® 

Base material: 1.4571 

Benefits to the customer: 

The austenitic stainless steel 1.4571, which is highly chemical-resistant, is used as the base material. 

To minimize costs, the ball is given a KVT 231® chromium carbide coating, which is extremely hard (900-1,100 HV/0.3) and provides adequate protection against abrasion and chemical reactions. 

The KVT 433® coating, applied using the spray-and-fuse process, is selected for the washer. The high tungsten carbide content in this coating makes it hard enough and gives it the required edge stability. This weld-on/fused coating is a little more expensive, but features a metallurgical bond and a thickness of 0.5 mm. Moreover, the fact that the coated surface on the washer is relatively small and does not require much material means that investments are quickly recouped thanks to a longer lifecycle. 

Context: 

Large volumes of ball valves are needed to build plant and pipelines for the transportation and processing of natural gas. Valves used in the gas flow are subject to severe abrasion and chemical corrosion. 

Use of the base material 1.0566 TStE and a tungsten carbide coating is prescribed by the customer. 

In addition to the prescribed coating, the components also need to be protected against chemical corrosion. 

Industries: 

Gas industry, pipeline construction, gas scrubbing and gas processing 

KVT solution: 

Coating method: HVOF 

Coating material: KVT 175® and chemical nickel (NiP) 

Base material: 1.0566 

Benefits to the customer: 

High-velocity oxygen fuel spraying (HVOF) applies little thermal energy but a lot of kinetic energy. As such, it strikes the right balance between adhesive strength for the coating and minimal stress for the base material. It can also be applied to all common materials. 

KVT 175®, which has a tungsten carbide content of 86 percent, is prescribed as the material for the coating. This coating is very wear-resistant, boasts a hardness of 1,400 HV/0.3, is between 0.15 and 0.2 mm thick and has a porosity of less than 0.5 percent. At the same time, it is resistant to acids, caustic solutions and corrosive gases. 

Before being coated with KVT 175®, the prepared black steel components are first electroplated with chemical nickel to ensure comprehensive protection against chemical corrosion. The hard coating is then applied on top of the electroplating, which significantly reduces the cost of materials for sealing systems. 

This combination of coating layers is one of the most inexpensive but also most resilient ways to create high-grade metal-seated ball valve sealing systems. 

Context: 

Valves made of Inconel are needed for the chemical industry. 

Given a nominal size of DN 200, however, it would be extremely expensive to make the entire valve body from Inconel. 

The medium contains natural sediments that have an abrasive effect when subject to high flow velocities. It also contains aggressive chemical components that would even react with normal stainless steels. 

The assemblies are safety-critical and must never be allowed to fail in their entirety. 

KVT solution: 

Coating method: Laser, spray-and-fuse process 

Coating material: KVT 404®/KVT 433® 

Base material: 1.4462 

All internal parts of the valve that come into contact with the medium are cladded using the laser-welding method. The points at which seals and washers are affixed are turned to create a perfect fit to tolerances of within a few hundredths of a millimeter. 

Balls and washers are flame-sprayed and fused with a combination of KVT 404 and KVT 433. The components are lapped against each other in pairs for an impermeable fit. 

Benefits to the customer: 

Cladding the valve with Inconel avoids the expense of using solid materials and reduces production costs for the valve body by more than 50 percent. The material is subject only to superficial thermal stresses and retains its full mechanical performance capabilities. 

The laser-welding method creates a permanent metallurgical bond between the substrate and the protective Inconel cladding. This eliminates the threat of sub-surface corrosion and the resultant risk that the cladding might flake off. 

Over more than three decades, the combination of KVT 404 and KVT 433 hard alloy coatings has proven itself in thousands of installations involving all kinds of media. It also delivers the longest known service lives in the industry. Thanks to a high nickel content, these coatings are very well protected against chemical corrosion. The spray-and-fuse process produces virtually non-porous coatings,  and the metallurgical bond almost completely precludes the possibility of sub-surface migration.