The　morphology,　the　distribution　and　crystallographic　orientation　of　TiB　in　situ　formed　in　TiB/Ti-6Al-4V　composite　coatings　by　laser　were　observed　by　TEM　and　EBSD,　in　order　to　explore　the　formation　mechanism　of　tubular　TiB.　The　results　show　that　TiB　grains　exhibit　two　morphologies:　rod　and　needle,　and　which　are　controlled　by　growth　time　and　element　concentration.　Rod-like　TiB　nucleate　in　the　hypereutectic　region,　while　needle-like　TiB　nucleate　in　the　eutectic　and　hypoeutectic　region.　The　growth　of　(010)B27　and　(001)Bf　planes　would　no　longer　be　stable,　when　the　diameter　and　the　growth　rate　of　TiB　exceed　their　critical　values.　The　growth　rate　in　the　edge　region　of　TiB　is　faster　than　that　in　the　center　due　to　the　concentration　of　boron.　TiB　grains　eventually　form　a　tubular　structure　because　boron　element　is　consumed　by　the　growth　of　edges　that　further　inhibits　the　growth　of　the　central　region.　With　the　increase　of　diameter　of　TiB,　the　tubular　structure　appears　more　frequently.　©　2018,　Northwest　Institute　for　Nonferrous　Metal　Research.　Published　by　Elsevier　BV.　All　rights　reserved.