 Proceedings of Engineering and Technology Innovation , vol. 4, 2016, pp. 13 - 15 13 Improving the Weldability of Nickel-Based Superalloy by High Frequency Vibration Ti-Yuan Wu 1,* , Ming-Tzer Lin 1 , Weite Wu 2 1 Institute of Precision Engineering, National Chung Hsing University, Taichung, Taiwan. 2 Department of Materia ls Science and Engineering, National Chung Hsing University, Ta ichung , Taiwan. Received 22 February 2016; received in revised form 15 March 2016; accept ed 13 April 2016 Abstract The objective of this paper is to discuss the weldability of Mar-M -004 nic kel-based alloy by simu ltaneous proceeding vibration. Three kinds of vibration modes were chosen to compare the results, including high frequency vibration, subresonant and without vibration . We used x-ray diffraction (XRD) to quantize the residual stress of each sample, a ls o the microstructure and crystal structure were investigated by using optical microscopes. The results showed that the grain size will get refined after vibrat ion we lding, especially in high frequency vibration. Fro m XRD and mi- crostructure results, by using the high frequency vibration method, there has a significant effect of having lowest residual stress and lowest stress rela xation; furthermore, the formation of cracks was also inhib ited and having the shortest crack length. Ke ywor ds : vibratory stress relief, residual stress , welding crack, nickel-based super- alloy, high frequency vibration 1. Introduction Nic ke l-based alloy has the properties of high strength and high corration resistance in high temperature [1]. Ho wever, Mar-M-004 n ick- el-base superalloy contains high levels of tita- nium and alu minum. While cooling after we ld- ing, a large nu mber of γ 'phase will be prec ipi- tated, and produce large shrinkage stress es, which will result in c racking and having poor weldabilities [2]. Vibratory stress relief (VSR) is effective in reducing the residual stress, prevending defo r- mat ion and increasing the materia l’s strength. Furthermore, it has advantages of energy saving, without pollution, low cost, high efficiency and easy to operate [3]. Besides , simultaneously apply the vibration force wh ile we lding, which can properly in- crease the atoms’ mobility in high te mperature, will have a better effect of stress relie f and refine the microstructure [4]. Bonal Corporation has developed a tech- nique of subresonant vibration, which uses the frequency of 1/3 of resonant amplitude to do VSR. This d iscusses have got the world wide adoption,also been recognized in the papers published[5]. Fig. 1 Waveforms and spectrums of different VSR modes , (a) high frequency vibration (b) subresonant (c) resonant We have developed a new approach of high frequency vibratory stress relief, wh ich use a low-frequency wave to stimulate a h igh fre - quency comple x waveform. Thus, this technique has been proved to be more effective to promote local dislocation move ment and reduce the re- sidual stress [6]. 2. Method This e xperiment is the use of Nd: YA G laser weld ing s imultaneously input vibration to fill (a) (b) (c) * Corresponding aut hor. Email: paxon1992911@gmail.com Proceedings of Engineering and Technology Innovation, vol. 4, 2016, pp. 13 - 15 14 Copyright © TAETI blind holes . Both the filler and the base materia l are Mar-M-004 nickel-base superalloy. As Fig. 2, the VSR apparutus composed of a vibration motor input a vibration wave to the workp iece and scaning the operating frequency of different VSR modes. Fig. 2 Schematic of vibration welding process 2.1. Processing Steps (1) Scanning the spectrum, subresonant and high frequency point of the workpiece. (2) Using subresonant53.1Hz, high frequency 51.7Hz 50.4Hz and without vibration to do simultaneous vibration welding. (3) For each vibration modes, fill two blind hole on the nickel-based alloy plate. 2.2. Sample Analysis (1) Using Cr-XDR to measure the residual stress value. (2) Using OM and SEM to observe the mic ro- structure. 3. Results and Discussion Fro m Fig. 3, the residual stress in weld bead is highest without vibration and lowest while using high frequency vibration , also, by cutting the weld bead to relax the stress . Fig. 3 Vibration modes -residual stress diagram Fig. 4 shows the mic rostructure of the weld bead. While using high frequency vibration weld ing, there has the least cracks in fusion line and the shortest crack’s length in fusion zone. Fig. 4 Bead cross -section (a) no vibration 0Hz (b) high frequency vibration 50.4Hz (c) high frequency vibration 51.7Hz (d) subresonant 53.1Hz Fig. 5 Mic rostructure of weld bead (a) no vi- bration 0Hz (b) high frequency vibration 50.4Hz (c ) high frequency vibration 51.7Hz (d) subresonant 53.1Hz As the crystal structure in Fig. 5, vibration weld ing can form equia xed dendritic g rains in contrast to the columnar dendrit ic grains without vibration. It represent that the solidification and cooling rate a re faster, and have the better gra in structures. Furthermore, the high frequency vibration can form a optimu m structure as compare with other vibration methods. 4. Conclusions Summarize the total results, high frequency vibration we lding possessed grain refine ment, lowest residual stress and reduce the cracks , which can effective ly get a better mechanica l properties and weldability of nic kel-based super alloy. Acknowledgement The authors are grateful to all colleagues and students who contributed to this study. Vibration motor Welding direction Laser beam Specimen Weling wire A: Subresonat 53.1Hz B: Wavelet 51.7Hz C: Wavelet 50.4Hz D: No vibration 0Hz A B C D 55 42 44 47 0 Hz 50.4 Hz 51.7 Hz 53.1 Hz 0 200 400 600 800 1000 1200 1400 1600 1800 S tre ss re la x tio n (% ) R e si d u a l st re ss ( M P a ) As welded Before cutting  Relaxtion (%) Frequency(Hz) 38 40 42 44 46 48 50 52 54 56 Without vibration subresonant High frequency Proceedings of Engineering and Technology Innovation , vol. 4, 2016, pp. 13 - 15 15 Copyright © TAETI References [1] S. Kou, Welding metallurgy, 2nd Ed., A John Wiey & Sons,Inc., New Jersey, pp. 263-300, 2003. [2] M. H. Haafkens and G. H. Matthey, “A new approach to the weldability of nickel-base as-cast and powder metallurgy superalloys,” Welding Journal, vol. 61, no. 1, pp. 25-30, 1982. [3] C. A. Walker, A. J. Waddell, and D. J. John- ston, “Vibratory stress relief - an investigation of the underlying process,” Process Institution Mechanical Engineers, vol. 209, pp. 51-58, 1995. [4] S. Weiss and S. Baker, “ Vibrational residual stress relief in a plain carbon steel weldment,” Welding Journal, vol. 55, 1976. [5] M. La x, “Stress relief technology”, Bonal Technology, lnc, 1986. [6] W. Wu, “Method for relieving residual stress in an object,” US 2009 /0049912 Al, 2009.