Laser Cladding of Inconel Using Huffman Machines

Laser Success Story Huffman Corporation invited TWI to collaborate in an application involving the laser cladding of Inconel 738 onto CMSX-4 Blades. The procedures developed are being used in production at a Tier 1 Component Casting facility for a major Industrial Gas Turbine OEM, to hard-face turbine blades for improved wear resistance.

Inconel 738 alloy is particularly susceptible to cracking during welding or cladding, and it is known to be very difficult to weld successfully with conventional welding techniques, such as TIG welding. However, the use of laser cladding minimizes the risk of cracking because of the low heat input involved. This characteristic is also of benefit when cladding onto single crystal substrates, because excessive heat will cause recrystallisation.

In addition to the material issues, production of the complex geometry of the turbine blade was challenging, as it required accurate positioning of the toolpath coordinates.

Objective

Develop a capability for the laser cladding of Inconel 738 powder onto CMSX-4 turbine blades.
Carry out process stability trials using the cladding procedures developed for testing and analysis.
Use the procedures developed to carry out a production run.

Equipment

Deposition trials were undertaken using Huffman HC-205 laser cladding machines, installed at TWI, Huffman and the Tier 1 facility. All the machines were equipped with Version 2.5 of the Huffman optical camera image recognition software ‘AutoClad’. This ‘vision’ system enables parts to be located and procedures applied rapidly in a production environment.

A PRC CO² laser, with a maximum power output of 2kW, was used for the trials at TWI. The procedure developed on TWI’s system was then used to assist the parameter determination for the other machines. Both Huffman and the Tier 1 used a 1kW IPG fibre laser for the work to produce a similar deposit.

Process Development At TWI, Yorkshire, UK

Process development was carried out at TWI to develop knowledge in the deposition of Inconel 738 powder onto the CMSX-4 substrate. CMSX-4 is a single crystal nickel based super-alloy, commonly used in engine components where high-temperature performance is required.

Initial trials were carried out on flat Inconel 718 plate using single track deposits. A combination of key process parameters, such as laser power, deposition speed and powder feed-rate were considered. Procedures were developed that showed no cracking when cross sectioned. Low penetration was desirable to reduce the heat input to the single crystal substrate minimizing any recystallisation.

Process Development At Huffman, Clover, SC

The process parameter set developed at TWI was used as a basis for the trials at Huffman. Because an IPG fibre laser was used as the laser source for the Huffman machine the power required was approximately half of that for the CO² laser at TWI. This is because of the reduced material interaction efficiency involved in using a 10.6µm wavelength CO² laser, as compared to a 1.064µm wavelength fibre laser.

After a series of trials, two sets of process parameters were selected for further examination at the Tier 1. Cross-section of samples created using these process parameter sets showed no unacceptable cracking in the deposits.

Process Development At Tier 1, USA

Procedures developed at Huffman were transferred to the Tier 1’s Huffman laser machine. An additional NC path was generated to follow the contour of the blade tip. An offset was introduced at the leading edge to change the skew angle of the blade tip.

The total processing time taken was less than 10 minutes, including loading and unloading of the component, capturing blade geometry and laser cladding. A number of blades were deposited, which were then heat-treated and cross-sectioned to examine the internal deposit quality.

Micrograph of laser deposit All the cross-sectioned samples showed acceptable deposit quality. Figure 2 (at left) shows a cross-section micrograph of deposit created using the final procedure. Inconel & Substrate Interface The micrograph shown in Figure 3 (at right) shows a narrow interface between the Inconel 738 deposit and the CMSX-4 substrate with no defects evident. Repeatable results were obtained in all the samples produced.

Figure 4 (below) shows a turbine blade, with the deposited material finished to blend-in with the remaining casting. No issues have arisen to date.

Conclusions

Procedures for the laser cladding of CMSX-4 blades using Inconel 738 developed at TWI and Huffman were successfully transferred to the Tier 1 Huffman laser cladding system.
No significant defects were seen in the bulk of the deposit or at the interface between the single crystal casting and deposit.
Repeatability trials show the process is stable and capable of depositing Inconel 738 onto CMSX-4 blades over a production run.

Huffman Corporation is always striving to make our customers profitable and efficient in their industries. We are proud to share these success stories to show you how you can be just as successful. Want to learn more? View our success cycle!

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	Laser Cladding of Inconel Using Huffman Machines Huffman Corporation invited TWI to collaborate in an application involving the laser cladding of Inconel 738 onto CMSX-4 Blades. The procedures developed are being used in production at a Tier 1 Component Casting facility for a major Industrial Gas Turbine OEM, to hard-face turbine blades for improved wear resistance. Inconel 738 alloy is particularly susceptible to cracking during welding or cladding, and it is known to be very difficult to weld successfully with conventional welding techniques, such as TIG welding. However, the use of laser cladding minimizes the risk of cracking because of the low heat input involved. This characteristic is also of benefit when cladding onto single crystal substrates, because excessive heat will cause recrystallisation. In addition to the material issues, production of the complex geometry of the turbine blade was challenging, as it required accurate positioning of the toolpath coordinates. Objective Develop a capability for the laser cladding of Inconel 738 powder onto CMSX-4 turbine blades. Carry out process stability trials using the cladding procedures developed for testing and analysis. Use the procedures developed to carry out a production run. Equipment Deposition trials were undertaken using Huffman HC-205 laser cladding machines, installed at TWI, Huffman and the Tier 1 facility. All the machines were equipped with Version 2.5 of the Huffman optical camera image recognition software ‘AutoClad’. This ‘vision’ system enables parts to be located and procedures applied rapidly in a production environment. A PRC CO² laser, with a maximum power output of 2kW, was used for the trials at TWI. The procedure developed on TWI’s system was then used to assist the parameter determination for the other machines. Both Huffman and the Tier 1 used a 1kW IPG fibre laser for the work to produce a similar deposit. Process Development At TWI, Yorkshire, UK Process development was carried out at TWI to develop knowledge in the deposition of Inconel 738 powder onto the CMSX-4 substrate. CMSX-4 is a single crystal nickel based super-alloy, commonly used in engine components where high-temperature performance is required. Initial trials were carried out on flat Inconel 718 plate using single track deposits. A combination of key process parameters, such as laser power, deposition speed and powder feed-rate were considered. Procedures were developed that showed no cracking when cross sectioned. Low penetration was desirable to reduce the heat input to the single crystal substrate minimizing any recystallisation. Process Development At Huffman, Clover, SC The process parameter set developed at TWI was used as a basis for the trials at Huffman. Because an IPG fibre laser was used as the laser source for the Huffman machine the power required was approximately half of that for the CO² laser at TWI. This is because of the reduced material interaction efficiency involved in using a 10.6µm wavelength CO² laser, as compared to a 1.064µm wavelength fibre laser. After a series of trials, two sets of process parameters were selected for further examination at the Tier 1. Cross-section of samples created using these process parameter sets showed no unacceptable cracking in the deposits. Process Development At Tier 1, USA Procedures developed at Huffman were transferred to the Tier 1’s Huffman laser machine. An additional NC path was generated to follow the contour of the blade tip. An offset was introduced at the leading edge to change the skew angle of the blade tip. The total processing time taken was less than 10 minutes, including loading and unloading of the component, capturing blade geometry and laser cladding. A number of blades were deposited, which were then heat-treated and cross-sectioned to examine the internal deposit quality. All the cross-sectioned samples showed acceptable deposit quality. Figure 2 (at left) shows a cross-section micrograph of deposit created using the final procedure. The micrograph shown in Figure 3 (at right) shows a narrow interface between the Inconel 738 deposit and the CMSX-4 substrate with no defects evident. Repeatable results were obtained in all the samples produced. Figure 4 (below) shows a turbine blade, with the deposited material finished to blend-in with the remaining casting. No issues have arisen to date. Conclusions Procedures for the laser cladding of CMSX-4 blades using Inconel 738 developed at TWI and Huffman were successfully transferred to the Tier 1 Huffman laser cladding system. No significant defects were seen in the bulk of the deposit or at the interface between the single crystal casting and deposit. Repeatability trials show the process is stable and capable of depositing Inconel 738 onto CMSX-4 blades over a production run. Huffman Corporation is always striving to make our customers profitable and efficient in their industries. We are proud to share these success stories to show you how you can be just as successful. Want to learn more? View our success cycle!