Study on slurry erosion of different heat-treated steel

Under guidance of Dr. Sourav Das Mitul Rawat12216013

Introduction

Tribology & Wear-loss of materials-wear debris

Abrasive Wear-Micro-cutting : sharp particle or hard asperity cuts the softer surface. Cut material is removed as wear debris.- Micro-fracture : generally occurs in brittle, e.g. ceramic material. Fracture of the worn surface occurs due to merging of a number of smaller cracks.- Micro fatigue : When a ductile material is abraded by a blunt particle/asperity, the worn surface is repeatedly loaded and unloaded, and failure occurs due to fatigue. - Removal of material grains : Happens in materials (i.e. ceramics) having relatively week grain boundaries.

Introduction

Mechanism of Erosive Wear-particle properties (size, shape and hardness)- fluid flow conditions (density of the fluid, angle of impingement, particle velocity, particle concentration in the fluid, nature of the fluid and temperature of the fluid), and -surface properties(hardness and microstructure, geometry component, fatigue, melting point

Introduction

Slurry pot erosion testers, in which the samples are attached at the ends of arms pointing out from a centre hub with bearings, see Fig.

Introduction

In tests, the sample holders rotate and the samples travel along a circular path in the slurry volume, and collisions between the sample surfaces and the slurry particles will lead to erosive wear [Wood & Wheeler 1998, Knuutila et al. 1999, Lathabai et al. 1998]. The tests are often conducted under vacuum for gas erosion testing. The method has been used, for instance, for studies on the erosive wear resistance of blades of helicopter rotors and gas turbine compressors [Wood & Wheeler 1998, Maozhong & Jiawen 2002].

Literature Review

Knuuttila et al. had designed the slurry erosion pot test in 1999 for studying slurry erosion of thermal oxide spray coatings Alumina & Chromia . They varied pH of the slurry to obtain a relation between erosion and pH of slurry. Large grit size and high density of thermal oxide caused higher wear rates.

Rambabu et al. investigated the sand slurry erosive wear behaviour of Ni-Cr-Si-B coating deposited on mild steel by flame spraying process under different test conditions.Erosive wear test using 20 and 40 per cent silica sand slurry at three rotational speeds (600, 800 and 1,000 rpm).Wear ratio between the uncoated sample and coated sample was used as a parameter to compare wear. Scanning electron microscope (SEM) study of wear surface showed that loss of material from the coating surface takes place by indentation, crater formation and lip formation and its fracture.

Finnie et al. explained the mechanism of erosion of ductile and brittle material.Erosion is maximum at 30 for ductile and 90 for brittle metals.In cutting erosion, a lip is formed at the beginning when erodent particles hit the surface.Subsequently other erodent particles deforms the lips into platelets.These chips are cutoff by subsequent impact and causes weight loss.Erosion for brittle materials is explained as mechanism of fragmentation and impact.The striking erodent particle fragments a part of metal / alloys and leads to weight loss

Amarendra et al. studied the effect of various heat treatments on slurry erosion behavior of 13Cr- 4Ni martensitic stainless steel (MSS) at different impingement angles.

The heat treatments given, involved the austenitization of cast steel at temperatures of 950 C, 1000 C and 1050 C for different soaking durations of 2, 4 and 6 h at each temperature. This was followed by oil quenching and tempering for 1 h at a 600 C air cooled. The tempered MSS showed 34% lower wear rate due to increased toughness and hardness.

Procedure

ElementsCMnSSiPAlTiCrN

Conc.0.14690.860.0080.0150.0240.0580.0120.02555ppm

jih

Different samples of steel were obtained under varying heat treatments.The sample concentration is shown in table.The microstructure formed is observed under SEM and characterised by R&D, Tata Steel.

Samples were treated under different conditions at R & D,Tata Steel; Compositions are

SampleTreatmentDurationTemperature

Sample 0Water Quenched4hr930

Sample 1Normalized1hr930

Sample 2Annealed1hr930

Procedure

Bars obtained are grinded and cut according to the experimental setup requirements. Additionally 5 samples of steel are grinded and cut to match the need of three additional dummy samples.Earth sand is obtained by digging the earth to simulate the working conditions similar to digging.The sand is dried in Oven at 250C for 12h.The sand is filtered to obtain uniform size of paricles around 210- 310 microns.Sieve sizes used were Tyler 20/28/48/65.Concentration of slurry is fixed and 1kg of sand was mixed with 10 kg of water with continous stirring to obtain uniform compostion.

Procedure

Weight of samples are measured precisely upto 0.0001 gm before and after the experiments.There are 4 four groves in holder at different angles of 30,45,60 & 90.In one grove the experimental sample is fixed and in other three standard dummy samples are fixed.The experimental setup and holder are shown below.

Procedure

The speed of tester is kept at two speeds 800 rpm and 500 rpm. With one experimental sample and three standard dummy samples , the holder is rotated in the slurry mixture at a fixed speed for varying duration of 30min and 1hr.After running the tests sample is cleaned and weighed.The weight loss is calculated for each sample.XRD and SEM analysis is obtained to the slurry erosion behaviour.

Results & Discussion

Comparison of Microstructure for std. Dummy samples before & after experiment

Comparison of SEM for exp. Samples before & after experiment

Hardness Variation

Wear Rate

XRD analysis

Profilometer

Future Scope

Change in Conc / Conditions

References

[1] Wen, DC.,Improvement of slurry erosion resistance of martensite/ferrite duplex stainless steel by hot rolling .Met. Mater. Int. (2010) 16: 13 [2] Zu, Jian Bo., Wear of materials by slurry erosion,ProQuest Dissertations Publishing, 1990. [3] J Kannuttila, Wet abrasion and slurry erosion resistance of thermally sprayed oxideCoatings, Wear 232 1999 . 207212[4] Finnie, I., Wolak, J. and Kabil, Y.H. (1967), "Erosion of metals by solid particles", Journal of Materials, Vol. 12, pp. 682-700.[5] M. Divakar , Effect of material surface hardness on erosion of AISI 316 , Wear 2005 , pg 110-117[6] HJ Amarendra, Slurry erosion of heat treated 13Cr-4Ni Martensitic stainless steel, Material Science Forum 2012 p500-505.[7] Rambabu Arji, Some studies on slurry erosion of flame sprayed Ni-Cr-Si-B coating ,Industrial Lubrication and Tribology , 2009[8] Prantik Mukhopadhyay, Microstructural developments during abrasion of M50 bearing steel , Wear 2004[9] Victor Jaimes, Abrasive Wear Assessment of X-70 Steel and PolyurethaneCoupons on a Modified Dry/Sand Rubber Wheel Apparatus , ProQuest Dissertations Publishing 2013[10] S. Das Bakshi , Three-body abrasive wear of fine pearlite, nanostructured bainiteand martensite, Wear 2013