How to process the Superalloy parts well with CBN Cutting Tools

Part 1 The meaning and features of Superalloy:

1.Superalloy: It Means a metal material based on iron, nickel, cobalt, can worked long-term under a high temperatures(more than 600℃) and certain stress, also called high temperature alloy.

2.Superalloy’s Features: It has a high temperature strength, good resistance to oxidation , corrosion resistance , good fatigue properties and resistance to fracture toughness. Superalloy is a single austenite tissue, Superalloy have a good organizational stability and reliability under a variety of temperature.

As the Superalloy’s characteristics ,it has become the key materials of the hot end component in aerospace engine, it is an important member of aerospace materials, and also widely used in petrochemical, power, metallurgy and other fields.

Part 2 The history of Superalloy:

High temperature material development from 1930s, in order to meet the needs of new engine, Superalloy walked into a period of vigorous development during World War II. Early 1940s, British adding a small amount of aluminum and titanium into 80 nickel-20 cobalt alloy firstly, researching the first nickel-based alloy with high temperature strength. During the same period, United States began to use cobalt-based alloy as blades of engine turbocharger in order to meet the needs of aviation piston engine.

In addition, United States also developed the nickel-based alloys for the combustion chambers production of jet engine. Then metallurgists added tungsten, molybdenum, cobalt and other elements in nickel-based alloys for improving the high temperature strength of the alloy further, increasing the content of aluminum and titanium, developed a series of alloy, the development of cobalt-based high-temperature alloy is still limited as the lack of cobalt resources.

Iron-based Superalloy have also been developed in 1940s, Incoloy901, A-286 and other model appeared in 1950s ,but its development was slow down since the 1960s since the high temperature stability is poor. The Soviet Union began product nickel-based Superalloy in 1950, and later produced wrought Superalloy and forging Superalloy. From 1956, China began trial production the high temperature alloys, then become wrought Superalloy and forging Superalloy later. For adopting the needs of increasing the inlet temperature of the aero-turbine United States manufactured directional crystallization blade and powder metallurgy turbine disk by new process.

Part 3 The high-temperature alloy’s classification:

(1)     Divided by the based elements:

It include iron-based Superalloy, nickel-based Superalloy and cobalt-based Superalloy. Where for the iron-based Superalloy, it is suitable for temperature in 600~800℃, nickel-based Superalloy suit 650 ~ 1000 ℃; cobalt-based Superalloy suit for 730~1100 ℃, but the development of cobalt-based alloy is limited since cobalt is an important strategic resource. Nickel-based Superalloy has a wider application currently.

(2)Divided by the way of strengthening:

Solid solution strengthening, precipitation strengthening type, oxide dispersion strengthened and reinforced fiber strengthened type,etc.

(3) Divided by Preparation process:

Wrought high temperature alloys, cast high temperature alloys and powder metallurgy Superalloy.

Part 4 The trouble and right method during processing Superalloys:

1.The trouble of machining high temperature alloy:

(1)The high temperature resistance performance improved the processing difficulty directly; (2)The tools easily crushed and deformed under the heavy cutting forces and high temperature during processing.

(3)Most superalloys will occur hardening phenomenon quickly, thus affecting the accuracy of the workpiece surface.

2.Superalloys processing methods:

(1) process alloy before workpiece hardening as far as possible ;

(2) Use the tool with a sharp cutting acute angle edge;

(3) Use the tools with high strength geometry tools;

(4) Use the tool which can improve the rigidity measures.

Currently, the tool which can process Superalloy include: carbide tools, coated tools, ceramic cutting tools, cubic boron nitride(CBN) cutting tools, as the carbide cutting tools and coated carbide tools have a low hardness , poor resistance to deformation, just suit for processing Superalloy with lower hardness.

Ceramic tools can machine high-temperature alloy, but only for finishing process. However, ceramic tools are more prone to gaps and debris especially during processing the cast iron with a sandy surface.

When processing the high-temperature alloys and other high hardness alloy material, often using cubic boron nitride(CBN) cutting tools. Cubic boron nitride cutting tools is the best tools choice for machining ferrous materials currently. Although CBN cutter has a high price, this tools has a better effect than carbide tools, coated tools and ceramic tool when machining the high temperature alloy.

Part 5 Machining high-temperature alloy with cubic boron nitride cutting tools:

At present, the best tools for processing Superalloy in China is CBN tools from Halnn superhard material Co.,ltd. Since the founded of Halnn Superhard tools company, offer the high-quality, high-performance tool products always. And being the first one to propose using overall polycrystalline cubic boron nitride tools to roughing parts, this way also match the high-speed and precision finishing requirement. Halnn Superhard tools company enjoy a high reputation in the superhard tools field.

Halnn company researched Cubic Boron Nitride(CBN) tools BN-K11 and BN-S200model for machining high temperature super-hard alloy(Superalloy) parts, those two tools are both belong to finishing tools, it is better to keep the cut depth less than 0.3mm for BN-K11.

Part 6 The case of CBN Tools machining the Superalloy:

(1)Halnn CBN tools BN-K11 machining medical equipment

Machining part: Hip supporter of the medical equipment;

Machining material: Cobalt-based alloys;

Work piece Hardness: HRC 35;

Processing Type: Finishing;

Insert grade:BN-K11;

Cutting parameters: depth of cutting a_p=0.15mm

Feed rate Fr=0.10mm/r

Cutting speed Vc=210m/min

Processing methods: dry cutting;

Processing results: Compared with some European brands PCBN inserts (as shown below): cutting speed is more quickly than the European brands, and tools life is also higher than the European brands .

(2) Halnn CBN tools BN-S200 machining nickel-base superalloy

Material: nickel-based alloy Inconel 718;

Machining nickel-based alloy hardness: HRC45-HRC47

(state precipitation hardening nickel base alloy);

Insert Model: BN-S200 grade CBN circular blade RNGN120400;

Processing Type: Finishing;

Cutting speed: 350 m/min;

Feed rate: 0.15 mm/r

Cutting depth: 0.5 mm;

                    

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