Following presentation shows how to overcome the hardfacing problems by introducing a new welding procedure known as Buffering process.

1. By
Gaurav Kale.
Sponsored Industry: KOSO INDIA, Pvt. Ltd,
Nashik.
K.K. Wagh Institute of Engg. Education & Research, Nashik

2. Hardfacing is a metalworking process
where harder or tougher material is applied
to a base metal.
WHAT IS HARDFACING?
Before Hardfacing:
After Hardfacing:

3. Hardfacing Materials:
1. Stellite:
• Grade 6
• Grade 12
Sr.No. Elements (%) Grade 6 Grade 12
1 Carbon 0.9-1.4 1.2-1.7
2 Silicon 2 1
3 Manganese 1 2
4 Phosphorous 0.016 0.016
5 Sulphur 0.015 0.015
6 Chromium 26-32 26-32
7 Nickel 3 3
8 Molybdenum 1 1
9 Iron 3 3
10 Tungsten 3-6 7-9.5
11 Cobalt Remaining (min
60%)
Remaining (min
60%)

4. FLAWS DURING HARDFACING:
Currently the industry is facing some problems in this
(Hardfacing) processes such as,
1. Cracks.
2. Porosity
3. Blowholes..
Cracks in the specimen:

5. Flaws overcome strategies:
 Modify the present Welding Process
Specification(WPS).
 Suggest the new procedure according to the
metallurgical properties of work piece if any.

6. Our Research and study:
 Removing flaws not possible just by modifying the
present WPS.
 We found a process in which the base metal is welded
first with intermediate hardness material.
• The process is known as Buffering Process.

7.  In buffering process, the material of intermediate
hardness between alloy steel and stellite is hardfaced
first on valve part and then hardfacing of stellite is
done.
 Here, we are using stainless steel for buffering.
Buffering Process:

8. Specimen creation:
Diameter : 100mm
Thickness:40mm

9. OUR OBSERVATIONS:
Stellite reacts differently with alloy steels.
Alloy steel is softer compared to cast steel

10. Hardfacing on alloy steel job with conventional
method:

11. Observations for hardfacing
(With convensional method):
Parameter Observations
Rotation speed meter 0.42 RPM
Powder speed 11.6 gm/min
Voltmeter 19.6 V
Ammeter 120 A
Powder gas 3.7 LPM
Center gas 2.6 LPM
Shield gas 6 LPM

13. Buffering process observations:
Welding process GMAW welding
Buffer Material SS 316L.
Preheat temperature 100-150℃
Interpass temperature 150℃
Current 182 A

14. •Stainless Steel.
•Manganese Steel.
•Nickel based steel.
•Copper based steel.
Stainless steel electrode:

15. BUFFERING ANALYSIS:
Specimen Testing:

16. Hardfacing on buffered specimen:

17. Parameter Reading
Rotation speed meter 0.42 RPM
Powder speed 11.6 gm/min
Voltmeter reading 29 V
Ammeter reading 130A
Powder gas 4.3 LPM
Centre Gas 5LPM
Observations for Hardfacing on buffered specimen:

18. CONCLUSION

19. Sr. No. Parameter Conventional
method
Modified
method
1
Rotation speed meter 0.42 RPM 0.42 RPM
2
Powder speed 11.6 gm/min 11.6 gm/min
3
Voltmeter 19.6 V 29 V
4
Ammeter 120 A 130 A
5
Powder gas 3.7 LPM 4.3 LPM
6
Centre Gas 2.6 LPM 5LPM
Comparison Between
Conversional welding and Hardfacing after Buffering
process: