DETERMINATION OFHARDNESS OF TITANIUM SAMPLE

Priyanshu 12518 Raghvendra 12528Proneet 12520 Rahul 12535Punkesh 12522 Ashutosh 12542

Tuesday Group 22014

Dept. of Materials Science & Engineering

Outline

Background: Introduction to indentation techniques

Objective: Determination of mechanical properties of titanium using Vickers

Micro Indenter

Work done: Polishing, etching, Indentation

Instruments: Metallographic polishing machine., Vicker’s Microindenter

Introduction

Hardness: Measure of material’s resistance to permanent deformation

Indentation : Technique for measuring hardness of a material

Some major indentation techniques: Brinell Hardness Test, Rockwell Hardness Test, Vickers Hardness Test

HR=E - e

Brinell

Rockwell

Vickers Hardness test

The Vickers hardness test consists of indenting the test material with a diamond indenter, in the form of a right pyramid with a square base and at an angle of 136 degrees between opposite faces subjected to a load.

Why?

• It is based on an optical measurement system.

• Indentation made is very small hence, it can be used for very thin foils, tiny surfaces, and small samples.

• It works for a large scale of hardness scale and does not destroy the specimen

• Accurate results for homogeneous materials

ProcedureSample preparation

Polishing:

• Silicon Carbide Abrasive strips (1/0, 2/0, 3/0)

• Metallographic polishing machine (Grit size: P320,P800,P1000,P1200,P2500)

• Cloth polishing (Semi finer liquid, finer liquid)

Etching:

with Kroll’s reagent

• Distilled Water(90 ml)

• HNO3 (8ml)

• HF (2ml)

Dipped in reagent(15 seconds) then Swabbed with cotton

ProcedureMicrostructure after polishing

Procedure

Indentation• Used a 136° pyramidal diamond indenter

• Four indents of load 200gf were made as a boundary to specify area of indentation

• Indenter is pressed into each grain within specified area with a load of 15gf

• The indenter is pressed into the sample by an accurately controlled test force.

• The force is maintained for a specific dwell time, normally 10 – 15 seconds.

• The size of the indent is determined optically by measuring the two diagonals of the square indent.

Procedure

Specified area for indentation:

Procedure

Microstructure of the specimen after making all

the indents

Calculation

where: P(=15kgf) is load d(avg) is average diagonalHV=Vickers Hardness no.

The size of the indent is determined optically by measuring the two diagonals of the square

indent.

Then Vickers hardness number is determined using d(avg):

Observation

Hardness values varies from one grain to another

Maximum Hardness : 344

Minimum Hardness : 41.8

Standard Deviation: 57.133

y = 29057x-2.01

R² = 0.995

0

50

100

150

200

250

300

350

400

0 5 10 15 20 25 30

Hardness vs Average Diagonal

Observation

0

2

4

6

8

10

12

14

16

18

20

1-50 51-100 101-150 151-200 201-250 251-300 301-350

Fre

qu

ency

of

Har

dn

ess

Hardness Intervel

Hardness Frequency Distribution

Inference

Hardness values are not consistent throughout the structure.

We inferred from the frequency distribution that the hardness values are lying in a particular range for most of the grain.

Acknowledgement

Dr. Nilesh Prakash Gurao

Ram Krishna Sir (Mechanical Lab, ACMS)

Chandrashekhar Sir, Samantha Ma’am

Mechanical Behavior Laboratory

Thank You!