Look at the demos "save", "wmf" or "fpvetorial" in the folder (lazarus)/components/tachart/demo/save of your Lazarus installation.
If you are on Windows only I'd recommend the wmf export which is well-understand by Word. See the "wmf" demo. You can even copy the chart to the clipboard as a metafile. But note: Since wmf support is Windows-only the required package TAChartWMF is not installed by default (Select menu "Package" > "Install/Uninstall packages", find TAChartWMF in the right list of packages "available for installation", Click "Install selection", then "Save and rebuild IDE" -- this takes some time after which Lazarus restarts with the new package installed.).