используйте загрузку formData, как описано ниже:
public upload(file: any): Observable<any> {
let headers: HttpHeaders = new HttpHeaders();
const params = new HttpParams();
const formData: FormData = new FormData();
if (file) {
formData.append('file', file, file.name);
}
return this.http.put(this.Url, formData, { headers, params })
.pipe(map((response: any) => {
return response;
}));
}