Experimental Investigation of Effect of Fe-Cr-C based Hardfacing on Wear Properties of Mild Steel

Experimental Investigation of Effect of Fe-Cr-C based Hardfacing on Wear Properties of Mild Steel

Ranjit Singh

Asst. Professor,

Dept. of Mechanical Engineering Lovely Professional University Jalandhar, India

Sudhanshu Kumar Pandey

M. Tech student Lovely Professional University

Jalandhar, India

AbstractAn experimental investigation was carried out to improve the wear properties of mild steel hardfacing it with Fe- Cr-C based hardfacing electrode. Shielded metal arc welding process was used to deposit 1 and 3 layers of the alloys over the mild steel base metal surface. In order to check whether the wear property is improved or not Pin on Disc wear test was performed. Hardness test was also performed and the microstructural observations of the samples were investigated using optical microscopy. It was found that Wear resistance increases by 79.48%, as the hardfacing layers are increased from 1 to 3. Hardness also increases by 32.26%, as the hardfacing layers are increased from 1 to 3.

Keywords Hardfacing ,POD, Mild steel, Buffer layer

1. INTRODUCTION

   Hardfacing is the deposition of a special alloy material on a metallic part, by various welding processes, to obtain more desirable wear properties or dimensions. The properties usually sought are greater resistance to wear from abrasion, impact, adhesion (metal-to-metal), heat, corrosion or any combination of these factors. A wide range of surfacing alloys is available to fit the need of practically any metal part. Some alloys are very hard; others are softer with hard abrasion resistant particles dispersed throughout. Certain alloys are designed to build a part up to a required dimension, while others are designed to be a final overlay that protects the work surface. [1] Hardfacing is the process of depositing of metal by one of various welding techniques, a layer or layers of metal of specific properties on certain areas of metal parts to resist wear, erosion, corrosion, high temperature, or impact. [2] Hardfacing can be done for a new part also while producing it and also for worn out part to re-establish the worn out portion. Thus hard-facing has capability to enhance service life of a part and there by extend life of equipment. Hardfacing can help reduce both maintenance and manufacturing costs. Maintenance costs are reduced because hardfaced parts are less likely to fail and therefore need to be replaced less often. Also, parts that would otherwise need to be replaced can be repaired using hardfacing. Production cost is also reduced because parts do not have to be made out of expensive metal alloys. They can be made out of less expensive metals and then hardfaced for strength.[ 3]

2. HARDFACING PROCEDURE

   The hardfacing alloy is deposited over the base metal surface by using shielded metal arc welding process. Fe-Cr-C based electrode is used to overlyed the surface of base metal. Such type of electrode is having the chromium as major constituents which provide better resistance against wear. Buffer layer is used before hardfacing and an interpass temperature of 250°C is maintained between subsequent passes. Once the buffer layer is applied the Fe-Cr-c hardfacing alloy is deposited over the surface by using shielded metal arc welding. The electrode used is having dia. 3.2mm and length 350mm.

3. EXPERIMENTATION

   1. selection of base metal

      For this research work mild steel was selected as base metal having chemical composition given below.

      Table I

      Chemical composition of base metal

      C	Si	Mn	P	S	Cr	Mo	Ni	Cu
      0.21	0.12	0.40	0.02	0.002	0.10	0.01	0.11	0.20

   2. Selection of hardfacing electrode

      Fe-Cr-C based hardfacing electrode was selected for the experiment and the chemical composition is given below.

      Table II

      Chemical composition of Fe-Cr-C hardfacing electrode

      C	Mn	Si	Cr	Mo	V
      0.60	0.70	0.50	6.2	0.45	0.30

   3. Selection of buffer eletrode

      The buffer layer electrode has been used to provide proper bonding between the base metal and hardfacing electrode. And their chemical composition is given below.

      Table III

      C	Mn	Si	S	P	Ni+Cr+Mo+V
      0.06	1.40	0.40	0.010	0.019	< 1.75

      C	Mn	Si	S	P	Ni+Cr+Mo+V
      0.06	1.40	0.40	0.010	0.019	< 1.75

      Chemical composition of buffer electrode

   4. Test to be performed

      The parameters selected for hardfacing the base metal is given in table IV.

      Sample no	Current	Hardfacing Layers
      1	180	3
      2	180	1
      3	150	3
      4	150	1

      Sample no	Current	Hardfacing Layers
      1	180	3
      2	180	1
      3	150	3
      4	150	1

      Table IV Parameters for test

      In order to investigate wear properties ASTM G99 Pin on disc wear test is performed. The specimens prepared are having dia.6mm and length 25 mm as shown in Fig.1.The pin on disc set up is shown in fig.2.

      Wear volume loss in mm3 = Weight loss / 10*D (1) Wear rate in mm3/Nm = Weight *10000/ S*D*T (2) Where

      D = density

      S= sliding distance T= time

      Disc rotation speed	250 RPM
      Disc dia.	80 mm
      Load applied	3 Kg
      Sliding distance	1500 meters
      Intervals	4
      Total time	24 min

      Disc rotation speed	250 RPM
      Disc dia.	80 mm
      Load applied	3 Kg
      Sliding distance	1500 meters
      Intervals	4
      Total time	24 min

      Table V Parameters for wear test

      Fig. 2 Pin on disc machine

4. RESULTS & DISCUSSION

   1. Wear test result Mass loss

   Wear resistance test is carried out to measure the increase in wear resistance of hard faced samples as shown in figure 3. Mass loss is measured durin the wear resistance test for the sliding distance of 1500 meters. Mass loss is minimum (0.0020 g) in sample number 3 followed by sample number 1 (0.0023 g), sample number 4 (0.0085 g), sample number 2 (0.0090 g) and base metal (0.0102). Sample number 3 has highest %age of chromium along with negotiable amounts of Mo and V. Cr increases wear resistance whereas Mo, V increases hardness. Mass loss is associated with presence of allowing elements and microstructure of an alloy/metal. Base metal mild steel has highest mass loss among all samples due to softer pearlitic phase in microstructure and unavailability of alloying elements as compared to other samples.

   Hardness test was performed at Punjabi University, Patiala. The hardness test is carried out by polishing the cross- sectioned samples with amri papers up to grade 2000 with a load of 500 grams.

   Microstructural observations have been taken by optical microscope at the magnification of 100X in Lovely University, Phagwara (Punjab). Prior to observations, the samples are polished and etched with 3% nital for 10 seconds.

   Fig. 1 Pins for wear test

   Fig. 3 Wear test result

   Wear volume loss

   Wear volume loss is measured in mm3 for the samples with the equation (1) Figure 4 shows wear volume loss is maximum in sample number 2 followed by sample number 4, sample number 1 and sample number 3. Wear volume loss gets decreased with sliding distance except for sample number 2, in which wear volume loss increases up to 1125 meters and then decreases. The decreased wear volume loss is associated with work hardening of substrate.

   high current (180 amperes) and single layer hardfacing High current result in slower cooling rates resulting in softer matrix having lower hardness. The hardness of mild steel is (250 HV) this is due to presence of relative softer phases than hard faced samples. Sample 1 has slightly low hardness (840 HV) than sample 3which is due to similar welding conditions except high current in sample 1 as compared to sample 3 which results in coarser dendritc segregation thereby reduced hardness. Figure 6 showing the plot b/w samples and hardness.

   Wear rate

   Fig. 4 Wear volume loss vs. sliding distance

   Wear rate is measured in mm3/Nm. Sample number 1 and sample number 3 shows least wear rate as compared to sample number 2 and sample number 4. Sample number 1 and sample number 3 have 5.22% and 5.19% of chromium as compared to 3.08% and 3.73% in sample number 2 and sample number 4 respectively as shown in figure 5. Higher amount of Cr in samples number 1 and sample number 3 decreased the wear rate as higher amount of chromium results in increased carbide formation which acts as barrier to the removal of material in wear, hence lower wear rate. Except Cr, other key elements in sample number 1 and sample number 3 are Mo and V, which tends to increase in hardness. As the hardness increases, there is decrease in wear rate. Wear rate decreases with time and tends to stable.

   Fig.6 Plot b/w samples and hardness

   C. Microstructural observations

   Wear resistance

   Fig. 5 Plot b/w Wear rate vs. time

   Wear resistance is reciprocal of wear rate. Wear resistance is maximum for sample number 3, which has minimum wear rate among all samples. Similarly sample number 2 has minimum wear resistance among all hardfaced samples with maximum wear rate Increased wear resistance is associated with presence of alloying elements and wear resistance particle in substrate. Sample number 1 and sample number 3 has higher amount of Cr, V and Mo causing better wear resistance than sample no 2 and sample no 4.

   1. Hardness test

      Hardness is maximum (871 HV) in sample number 3. In which lower current (150Amperes) and 3layers of hardfacing are used which produces finer grained structure as compare to single layered samples, causing an increase in hardness. Whereas sample 2has the lowest hardness (575HV) across all the hard faced samples except base metal. Which is due to

      Fig. 7 Microstructural observations

      All the hard faced shows a microstructure composed of martensite and retained austenite with a pattern of dendritic segregation which becomes more redefined as current has reduced. Sample no 1 and 3 shows microstructure tempered by subsequent passes produces further precipitation of small carbides whereas in sample 2 and 4 shows coarser grain as compared to sample no 1 and 3 due to slower cooling rates. Whereas base metal shows pearlitic phase embedded in matrix of ferrite. Figure 7 is showing the microstructural observations of samples.

5. CONCLUSION

1. Hardness and wear resistance increases with increase in hardfacing layers and decreases with increase in current.

2. Hardness increases by 32.26%, as the hardfacing layers are increased from 1 to 3.

3. Wear resistance increases by 79.48%, as the hardfacing layers are increased from 1 to 3.

4. Hardness and wear resistance decrease by 3.55% and 12.22% respectively with 16.66% increase in current.

REFERENCES

1. Afrox Product Reference Manual – Welding Consumables Hardfacing.

2. Kumar S , Mondal D.P , Khaira H.K , and Jha A.K (1999) improvement in high stress abrasive wear property of steel by hardfacing. JMEPEG vol. 8, pp. 711-715

3. Chatterjee S and Pal T. K (2006) weld procedural effect on performance of iron basedhardfacing deposits on cast iron substrate. Jour. Of mat. Proc. Tech. vol. 173, pp. 61-69.

4. Wang X. , Han F. and Shiyao D. (2008) microstructure and wear properties of Fe-Ti-V-Mo-C hardfacing alloy. Wear, vol. 265, pp. 583-589.

5. D. K. Dwivedi, ABRASIVE WEAR BEHAVIOUR OF IRON BASED HARD SURFACING ALLOY COATINGS DEVELOPED BY WELDING. 2004.

6. S. Kumar, D. P. Mondal, and A. K. Jha, Effect of Microstructure and Chemical Composition of Hardfacing Alloy on Abrasive Wear Behavior, JMEPEG, vol. 9, pp. 649655,2000.

7. Buchely M.F, Guttierz J.C and Leon L.M (2005) the effect of microstructure on abrasive wear of hardfacing alloys. Wear. Vol. 259, pp. 52-61.

8. Klimpel A. , Kik T. , Gorka J and Sitarz P (2009) SAW surfacing of low alloyed steel withsuper ferrite additional material. JAMME, vol. 36, issue 2.

9. Ilo S, Just Ch. , Xhiku F, (2012) optimisation of multiple quality characteristics of hardfacing using grey-based taguchi method. Materials and Design vol.33, pp. 459 468.

10. Fijisova N, James L. Natalie and Woodard J.C (2003) a novel pin-on apparatus.Wear,vol.254,pp.111-119.

11. G. Kocher, O. Parkash, and S. Vardhan, Hardfacing by Welding to Increase wear Resistance Properties of EN31 by MR 3LH Electrode, Int. J. Emerg. Technol. Adv. Eng. Website www.ijetae.com, vol. 2, no. 2, 2012.